Muscles doi: 10.3390/muscles5030050

Authors: Valentina Cavedon Chiara Milanese Carlo Zancanaro

Understanding the direct relationship between skeletal muscle mass and strength in athletes is paramount for optimizing performance. Such a relationship has been poorly investigated in soccer players. In this work, a large number (n = 225) of elite soccer players aged 14–37 years had whole-body (WB) and regional skeletal muscle mass (SMM) estimated from Dual-energy X-ray absorptiometry (DXA) scans, together with maximal isokinetic strength of several muscle groups. Results showed a statistically significant (p < 0.001) correlation between limb SMM or muscle strength and body mass (r = 0.84–0.86; r = 0.61–0.97, respectively) and stature (r = 0.58–0.64; r = 0.61–0.93, respectively), whereas the relationship with age was much more variable. A statistically significant (p < 0.001) correlation was found between SMM and muscle strength across all muscle groups (r = 0.55–0.80). Linear regression showed that SMM explained 30% to 64% of the variance in muscle strength. ANOVA showed that playing position had a statistically significant effect (p < 0.001) on all SMM and muscle strength values. Playing position had a significant effect on relative (normalized per-limb SMM) muscle strength during knee and ankle flexion. This work showed that DXA-measured skeletal muscle mass is associated with the strength of several limb muscle groups in soccer players. This association is of variable strength across muscle groups and is partially modulated by playing position.

Muscles doi: 10.3390/muscles5030049

Authors: Franziska Adams Matthias Kohl Simon von Stengel Andre Filipovic Michael Uder Wolfgang Kemmler

Background: Given its practical advantages in terms of time efficiency, joint compatibility and extensive adaptability, whole-body electromyostimulation (WB-EMS) has gained considerable attention as a training method among athletes and sportspeople across numerous disciplines. The present systematic review and meta-analysis aimed to determine the impact of WB-EMS on maximum hip/lower-extremity strength and power. Methods: A systematic search of five literature databases was carried out up to 30 March 2025 in accordance with the PRISMA scheme. Effect sizes (SMD) and 95–confidence intervals (95–CI) were derived using a random-effect model incorporating the inverse heterogeneity approach. Results: Nineteen WB-EMS and 21 control groups were included. Overall, we observed favorable effects of this novel training technology on maximum strength (18 trials, SMD: 0.62, 95–CI: 0.08 to 1.16, I2 = 86%)) and power (8 trials, SMD: 0.38, 95–CI: 0.06 to 0.70, I2 = 15%). Subgroup analyses examining superimposed WB-EMS relative to voluntary exercise alone yielded low to moderate, yet statistically non-significant, effects on maximum strength (12 trials, 0.44, −0.20 to 1.08, I2 = 85%) and power (7 trials, 0.39, −0.02 to 0.81, I2 = 35%). Studies addressing the comparison of superimposed or non-superimposed WB-EMS against traditional dynamic resistance exercise reported largely equivalent outcomes for both strength and power development. Conclusion: Contingent upon the mode of application (superimposed, additional or optional), WB-EMS may exert a positive influence on maximum strength and power in sportspeople and athletes.

Muscles doi: 10.3390/muscles5030048

Authors: Dai Qiyun Yoshinari Matsumoto Masao Katsushima Ryu Watanabe Yuya Fujita Shinsuke Yamada Daiki Habu Motomu Hashimoto

Accurate assessment of appendicular lean mass (ALM), an essential component for evaluating sarcopenia and nutritional status, typically requires dual-energy X-ray absorptiometry (DXA); however, its widespread clinical application is limited by cost and accessibility. This study aimed to develop a simple anthropometry-based equation for estimating ALM in women with systemic lupus erythematosus (SLE) and to compare its predictive performance with existing models. This cross-sectional study included 92 female patients with SLE. A multiple regression model was developed, incorporating height, body weight, calf circumference (CC), and age. Model performance was internally validated using five-fold cross-validation, and agreement with DXA-measured ALM was assessed using out-of-fold predictions. The diagnostic performance for detecting low skeletal muscle mass index (SMI) was also evaluated and compared with previously published equations (Hwang and Santos). The predicted ALM showed good correlation with measured ALM (R2 = 0.76) and moderate agreement (Lin’s concordance correlation coefficient [CCC] = 0.829), with a root mean square error of 1.38 kg. Sensitivity and specificity for detecting low SMI were 65.0% and 88.9%, respectively. The proposed equation demonstrated comparable or superior performance (CCC: Hwang 0.782; Santos 0.672) and may serve as a practical tool for estimating ALM in female patients with SLE.

Muscles doi: 10.3390/muscles5030047

Authors: Amir Hossein Ahmadi Hekmatikar Gema Santamaría Ana M. Celorrio San Miguel Enrique Roche Fatemeh Khodadadi Álvaro López-Llorente Diego Fernández-Lázaro

Background: Physical exercise is strongly recommended for breast cancer survivors due to its beneficial effects on physical function, metabolic health, and quality of life. Lactate, traditionally considered a metabolic byproduct of glycolysis, is increasingly recognized as a signaling molecule involved in metabolic regulation and exercise adaptation. However, exercise-induced circulating lactate responses in breast cancer survivors remain poorly characterized. The aim of this systematic review and exploratory meta-analysis was to synthesize and critically appraise current evidence on exercise-induced circulating lactate responses in breast cancer survivors Methods: A systematic review and exploratory meta-analysis were conducted according to PRISMA guidelines and prospectively registered in PROSPERO (CRD42024504288). PubMed, Scopus, and Web of Science were searched to identify controlled trials investigating exercise-induced changes in circulating lactate concentrations in breast cancer survivors. Random-effects meta-analysis was performed using pooled mean differences. Results: Among 173 screened records, four studies met eligibility criteria for qualitative synthesis and three contributed to quantitative analysis. Pooled results demonstrated no statistically significant effect of exercise on circulating lactate concentrations (weighted mean difference: 0.03 mmol/L; 95% CI: −0.24 to 0.31; p = 0.81), with low heterogeneity (I2 = 31.1%). Considerable variation was observed across exercise protocols, intervention duration, and lactate assessment timing. Conclusions: Exercise-induced circulating lactate responses in breast cancer survivors appear modest and inconsistently reported across available studies. Current evidence remains limited by small sample sizes and methodological heterogeneity. These findings provide a physiological overview of lactate responses to exercise in breast cancer survivorship and highlight the need for standardized exercise interventions and metabolic outcome assessment in future research.

Muscles doi: 10.3390/muscles5030046

Authors: Felipe Yuji Koyama Azeka Paulo de Lima Serrano Daniel Delgado Seneor Sophia Luiz Calegaretti Mateus Medeiros Pinheiro Marcos Vinícius Martins Leonardo Mobiglia Guilherme João Paulo Barile Patrícia Marques Mendes Lucas Henrique de Moura Rogério Garcia Maria Júlia Tabosa de Carvalho Galvão Sofia Mônaco Gama Renan Brandão Rambaldi Cavalheiro Igor Braga Farias Roberta Ismael Lacerda Machado Wladimir Bocca Vieira De Rezende Pinto Acary Souza Bulle Oliveira Paulo Sgobbi

Congenital Myasthenic Syndrome represents a complex and heterogeneous group of inherited neuromuscular disorders, which result from variants in genes involved in different pathophysiological mechanisms related to the neuromuscular junction. LRP4 (Low-density lipoprotein receptor-related protein 4) represents one of the most important proteins involved in this complex signaling pathway, acting in a complex with agrin and Muscle Skeletal Receptor Tyrosine Kinase (MuSK) proteins. LRP4 became known to most neurologists due to the description of anti-LRP4 antibody-related Myasthenia Gravis. There are, however, different neurological and neuromuscular disorders that result from pathogenic variants in LRP4 gene, especially a rare and potentially treatable Congenital Myasthenic Syndrome. The authors performed a detailed narrative review, including descriptions of the main pathophysiological, clinical, and therapeutic aspects of LRP4-related Congenital Myasthenic Syndromes.

Muscles doi: 10.3390/muscles5020045

Authors: Joévin Burnel Benoit Vallee Benoit Pairot de Fontenay Joachim Van Cant

Hip joint position sense (JPS), a key component of neuromuscular function arising from muscle spindle and periarticular mechanoreceptor input, remains underexplored, with no standardized and reliable clinical protocol available to assess hip proprioception. This study evaluated the intra- and inter-rater reliability of a laser- and inclinometer-based active hip JPS protocol and established preliminary references in healthy adults. A two-phase reliability study was conducted in accordance with GRRAS and COSMIN guidelines: 17 participants for reliability analyses and 57 for preliminary references. Six movement directions were assessed (flexion, extension, abduction, adduction, medial and lateral rotations). Reliability was quantified using intraclass correlation coefficients with their 95% confidence intervals, using two-way random-effects models with absolute agreement (ICC(3,1) for intra-rater and ICC(2,1) for inter-rater analyses), interpreted as poor (<0.50), moderate (0.50–0.70), or good (≥0.70). Absolute measurement error was reported as standard error of measurement (SEM%) and 95% minimal detectable change (MDC95%), normalized to target amplitudes to allow direct cross-direction comparison. Intra-rater reliability ranged from poor to moderate, with experienced raters reaching ICC = 0.64 (95% CI [0.39; 0.80]) for medial rotation. Inter-rater reliability improved across sessions, peaking for medial rotation (ICC = 0.78; 95% CI [0.50; 0.91]). Rotational movements yielded the lowest SEM% (3–6%), indicating high measurement precision despite trial-to-trial variability (MDC% 9–31%). Normative errors were largest in flexion (21.4 cm) and smallest in rotations (≈2.2–2.3°). Despite overall low-to-moderate reliability, the protocol achieved clinically acceptable measurement precision (SEM% < 10%) for rotational tasks, whereas the laser-based sagittal and frontal-plane components remained exploratory. The protocol provides preliminary reference values for hip JPS in healthy adults and requires further validation before clinical use.

Muscles doi: 10.3390/muscles5020044

Authors: Yifan Chen Tianzheng Yu

Micronutrients are essential for optimal muscle metabolic function. We previously showed that heat-induced skeletal muscle injury is associated with depletion of nicotinamide adenine dinucleotide (NAD+) and magnesium (Mg2+), and boosting NAD+ abundance with the precursor nicotinamide riboside (NR) improves skeletal muscle integrity against heat stress in male mice. In this study, we hypothesized that NR supplementation would prevent heat-induced skeletal muscle injury in female mice. Female 6-week-old C57BL/6J mice were orally administered vehicle or NR (185 mg/kg body weight) daily for 10 days. Subsequently, they underwent a single sham or heat exposure experiment. No significant differences in muscle NAD+ content were observed between vehicle and NR groups or between sham and heat groups. Heat groups showed significantly lower muscle Mg2+ levels compared to sham groups. In vehicle groups, heat exposure caused significant inflammation, oxidative stress, mitochondrial impairment, and apoptosis in skeletal muscle compared to the sham condition. NR treatment significantly reduced these alterations. While neither heat exposure nor NR affected muscle NAD+ homeostasis, the protective effects of NR on skeletal muscle against heat stress were similar to those observed in male mice. Together, our results demonstrate the preventive effect of NR on muscle heat injury in female mice. This effect is associated with anti-inflammatory and antioxidative activities, mitochondrial protection, and anti-apoptosis without NAD+ homeostatic alterations.

Muscles doi: 10.3390/muscles5020043

Authors: Harry Wilton-Clark Alishba Raza Toshifumi Yokota

The DMD gene is best known for its product dystrophin, a large rod-shaped protein that plays a critical role in muscular membrane strength and integrity. Mutations affecting dystrophin lead to Duchenne muscular dystrophy, a fatal X-linked disease characterized by muscular weakness and breakdown. In addition to the full-length dystrophin product that is most often associated with disease, the DMD gene also encodes multiple shorter isoforms of dystrophin with diverse functions. One isoform in particular, Dp71, has been increasingly found to play a wide variety of roles throughout the body. In this narrative review, we consolidate the numerous studies on Dp71 to provide a comprehensive foundation for future work. We outline and summarize the current state of knowledge on the role of Dp71 in the brain, the retina, and skeletal muscles, identifying current knowns and unknowns in the field. We also explore Dp71-based therapies currently being tested in the pre-clinical landscape and identify potential limitations for clinical translation.

Muscles doi: 10.3390/muscles5020042

Authors: Elisa Silva Correia Jéssika Martins Siqueira Gustavo Duarte Pimentel

Hemoglobin levels play an important role in oxygen delivery to skeletal muscle, and reduced levels may impair muscle function and contribute to sarcopenia, particularly in patients with cancer. The aim of the present study was to evaluate the influence of hemoglobin levels on muscle mass and function in patients with digestive tract cancer. Methods: Patients of both sexes aged up to seventy years with cancers of the digestive system undergoing surgical and clinical treatment at an oncology referral center were included. Hemoglobin levels were assessed using a blood count, and the risk of sarcopenia was estimated using the Mini Sarcopenia Risk Assessment (MSRA). A total of 82 patients were evaluated, with a mean age of 55.4 years. Colon cancer was the most prevalent (41.6%), followed by rectal (18.3%) and stomach (14.6%) cancers. The risk of sarcopenia was estimated at 85.4%, and the prevalence of low hemoglobin levels was 71.9%; 35.4% of patients presented moderate hemoglobin depletion. Hemoglobin levels showed a moderate correlation with gait speed and a slight correlation with calf circumference, handgrip strength, and MSRA score. In conclusion, the risk of sarcopenia and low hemoglobin levels are present in patients with digestive tract cancer. Additionally, hemoglobin levels positively correlate with indicators of muscle function and the risk of sarcopenia.

Muscles doi: 10.3390/muscles5020041

Authors: Andrei Cretu Eliza-Maria Bordeanu-Diaconescu Catalina-Stefania Dumitru Cristian-Vladimir Vancea Mihaela-Cristina Andrei Adriana Serban Cristian-Sorin Hariga Cristian-Radu Jecan Ioan Lascar Andreea Grosu-Bularda

Quadriceps muscle and tendon injuries are a significant cause of impairment of the knee extensor mechanism, ranging from minor muscle strains to complete tendon ruptures and extensive defects following oncologic resections. This narrative review provides a comprehensive analysis of contemporary concepts in anatomy, biomechanics, diagnosis, surgical management, and rehabilitation, with a particular focus on reconstructive techniques and functional outcomes. While most muscle injuries respond well to conservative management, complete quadriceps tendon ruptures typically require surgical repair to restore extensor continuity. Both transosseous suture techniques and suture anchor fixation demonstrate reliable outcomes, with no clear superiority in clinical results. Chronic ruptures present additional challenges due to tendon retraction and poor tissue quality, often necessitating advanced reconstruction methods such as V–Y tendon lengthening and augmentation with autografts, allografts, or synthetic materials. In cases of large defects, especially following soft-tissue sarcoma resection, free functional muscle transfer (FFMT) has emerged as a key reconstructive strategy. Common donor muscles include the latissimus dorsi, gracilis, rectus abdominis, and vastus lateralis, each offering specific biomechanical advantages. Functional recovery is strongly influenced by the extent of quadriceps preservation, with better outcomes observed when at least two muscle heads remain functional. Rehabilitation protocols vary depending on the surgical approach. Early controlled mobilisation is generally recommended after tendon repair, whereas FFMT requires a more cautious and prolonged rehabilitation process to allow for flap integration and reinnervation. Overall, optimal outcomes depend on a multidisciplinary approach combining appropriate surgical technique, individualized rehabilitation, and careful patient selection.

Muscles doi: 10.3390/muscles5020040

Authors: Hyeon Yu Kevin Wang

Purpose: To develop a fully automated 2D nnU-Net pipeline for multi-class skeletal muscle segmentation (psoas, paraspinal, and abdominal wall) at the third lumbar (L3) vertebral level, and to quantitatively evaluate its diagnostic performance and reliability compared to manual segmentation. Materials and Methods: A 2D nnU-Net was trained on 164 axial L3 CT slices from the multi-institutional AMOS22 dataset, spanning diverse abdominal pathologies and multivendor imaging. To assess generalizability under severe anatomical distortion, independent external validation was performed in 50 consecutive patients with advanced liver disease from a single institution (January–December 2025; mean age, 63 ± 15 years; 32 women, 18 men), of whom 88% had moderate-to-severe ascites. Model stability was examined by comparing a five-fold ensemble with the best-performing single-fold model. Intra-observer reliability of the manual reference standard was evaluated in a random subset of 30 cases. Inter-observer agreement was additionally assessed using an independent second reader. Performance metrics included the Dice Similarity Coefficient (DSC), Pearson correlation coefficient (r), and Bland–Altman analysis for cross-sectional areas and mean attenuation. The inference workflow was deployed via a custom Streamlit-based graphical user interface (GUI). Results: In this anatomically complex external validation cohort, the 5-fold ensemble 2D nnU-Net achieved an overall mean DSC of 0.937 ± 0.043 (95% CI, 0.925–0.950), with 80% of cases achieving a mean DSC ≥ 0.90. While the mean DSC was statistically comparable to the best single-fold model (0.937, [95% CI, 0.921–0.952], p = 0.736), the ensemble strategy increased the minimum observed DSC (worst-case performance) from 0.720 to 0.822. Class-specific external validation performance for the 5-fold ensemble was highest for the paraspinal muscles (DSC: 0.960; 95% CI, 0.952–0.967), followed by the psoas muscles (DSC: 0.941; 95% CI, 0.927–0.956), and lowest for the anatomically complex abdominal wall muscles (DSC: 0.911; 95% CI, 0.893–0.929). Comparison between the ensemble model and manual segmentation yielded a Pearson correlation of r = 0.955 (p < 0.001) for total skeletal muscle area, with a mean bias of +7.17 cm2. Intra- and inter-observer agreements for the manual reference standard demonstrated correlation coefficients of r = 0.995 and 0.090 for total areas, respectively. The automated pipeline required 3–5 s per case for inference and quantitative reporting, compared to 3–5 min for manual segmentation. Conclusions: In patients with advanced liver disease and substantial anatomical distortion from ascites, an ensemble-based 2D nnU-Net provides high quantitative agreement with manual L3 skeletal muscle segmentation, while mitigating lower-bound (worst-case) errors relative to single-fold models. Integration with a dedicated GUI enables substantial time savings and supports scalable quantitative body composition measurement.

Muscles doi: 10.3390/muscles5020039

Authors: Victoria C. Sanfrancesco Daniella Della Mea David A. Hood

To maintain homeostatic conditions and optimal function during stressors, mitochondria initiate retrograde signaling. The mitochondrial integrated stress response (ISR) and unfolded protein response (UPRmt) are critical quality control mechanisms activated during instances of mitochondrial perturbations. Restoration of mitochondrial homeostasis is orchestrated by three transcription factors, ATF4, CHOP, and ATF5, which upregulate protective genes to counteract stress. As the health and function of skeletal muscle are heavily dependent on a highly adaptive mitochondrial network, defining how mitochondrial health is maintained across various conditions is essential. Although several studies demonstrate the importance of these responses following instances of stress, the signaling mechanisms required to initiate such pathways remain poorly characterized in skeletal muscle. This review examines how the mitochondrial ISR/UPRmt and related transcription factors respond to organellar stress by emphasizing the molecular events that occur during exercise, aging and muscle disuse. By consolidating the literature, this work aims to highlight the current understanding of mitochondrial stress response signaling within skeletal muscle and thus emphasize areas for future research and potential therapeutic strategies during divergent metabolic conditions.

Muscles doi: 10.3390/muscles5020038

Authors: Shilpa Sharma Danielle Debruin Jeannie Devereaux Alan Hayes Kulmira Nurgali Gustavo Duque

Muscle wasting contributes substantially to inflammatory bowel disease (IBD)-related disability, but its association with colitis severity across disease stages remains poorly characterized. We therefore assessed skeletal muscle mass, fiber morphology, and voluntary wheel-running performance in Winnie mice—a spontaneous Muc2 mutant model of chronic colitis—in separate female and male homozygous mutant and WT littermate cohorts. Assessments were performed at 5 weeks, before overt colitis, and at 15 weeks, in a cohort with more pronounced colitis. Outcomes included disease activity index (DAI), fecal lipocalin-2 (LCN-2), wheel-running metrics, soleus and tibialis anterior mass, and minimal Feret’s diameter distributions. At 5 weeks, Winnie mice showed no overt disease activity and no consistent structural muscle deficit. In contrast, the 15-week cohort exhibited marked colitis in both sexes, with increased DAI and LCN-2, reduced voluntary wheel-running performance, lower soleus and tibialis anterior mass, and smaller muscle fiber diameters with left-shifted size distributions. Correlation analyses identified associations between fecal LCN-2, skeletal muscle mass and size, and wheel-running distance and velocity, supporting a link between intestinal inflammation and muscle impairment in this model. These cross-sectional data are consistent with reduced voluntary activity and structural myopathy during progression of spontaneous colitis. The Winnie mouse model therefore provides a clinically relevant preclinical platform to study IBD-associated muscle wasting and its association with intestinal inflammation.

Muscles doi: 10.3390/muscles5020037

Authors: Filippos Christodoulou Petros Maniatis Andreas Erotocritou Stelios Hadjisavvas Michalis A. Efstathiou Irene-Chrysovalanto Themistocleous Manos Stefanakis

Background: The Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST) is used to assess upper-extremity performance in a closed kinetic chain position. The standard hand placement of 36 inches may favor individuals with larger body dimensions. Methods: Sixty-five healthy adults (44 males, 21 females; 18–33 years) performed the CKCUEST under two conditions: the standard position and a modified position with hand distance set at 50% of arm span. The mean number of touches, standard score, and power score were calculated for each condition. Reliability and the effects of sex and body composition were also examined. Results: Performance was significantly better in the modified position for mean touches (24.4 ± 4.47 vs. 23.0 ± 4.62, p = 0.001), standard score (0.4 ± 0.07 vs. 0.3 ± 0.06, p = 0.001), and power (81.1 ± 18.29 vs. 77.1 ± 22.00, p = 0.001). Both conditions showed excellent reliability (ICC = 0.944–0.946). Females performed significantly fewer touches than males in the standard position (p = 0.001), whereas this difference was not significant in the modified position. Several anthropometric and body composition variables significantly predicted performance. Conclusions: An arm-span-adjusted hand position improves CKCUEST performance and may provide a fairer assessment across individuals with different body dimensions.

Muscles doi: 10.3390/muscles5020036

Authors: Chi Ngai Lo Marcus Kwong Lam Fung Bernard Pui Lam Leung

Background: Musculoskeletal pain remains a major cause of disability worldwide, encompassing disorders such as rheumatoid arthritis (RA), osteoarthritis (OA) and chronic back pain. Acupuncture and dry needling are increasingly used for symptom management, yet their effects on inflammatory modulation remain unclear. This systematic review and meta-analysis evaluated the influence of acupuncture on inflammatory biomarker regulation in musculoskeletal pain. Methods: Following PRISMA and Cochrane methodological guidelines, comprehensive searches were conducted across MEDLINE (via PubMed), Web of Science, Cochrane Library, Scopus, Google Scholar, and OpenEvidence from inception to August 2025. Eligible studies were randomized controlled trials (RCTs) involving acupuncture or dry needling interventions with inflammatory biomarker outcomes. Screening, data extraction, and risk of bias assessment using ROB2 were performed by two reviewers independently. The certainty of evidence was appraised using GRADE criteria. The protocol was registered on PROSPERO (CRD420251011831). Results: Nineteen RCTs and one randomized cross-over study (n = 1492) met inclusion criteria. Some studies demonstrated reductions in CRP, ESR, IL-1β, IL-6 and TNF-α following acupuncture. Random-effects meta-analysis indicated that modified acupuncture (electroacupuncture or needle-knife therapy) significantly reduced TNF-α in knee OA compared with traditional acupuncture (SMD = −1.63, 95% CI −2.47 to −0.80, p < 0.01) but not IL-1β. However, no significant effects were observed from acupuncture versus sham acupuncture for CRP or ESR in patients with arthritis. However, the findings are limited by high heterogeneity and the small number of studies included in each meta-analysis. Conclusions: A moderate level of GRADE evidence suggests that modified acupuncture may be more effective than standard acupuncture in reducing TNF-α levels in patients with OA. Further high-quality biomarker-based RCTs are warranted to confirm these findings. This study received no external funding.

Muscles doi: 10.3390/muscles5020035

Authors: Bana Abolibdeh Charles H. Williams

Centronuclear myopathy (CNM) is a genetically heterogenous congenital myopathy traditionally classified as a membrane remodeling disorder. Emerging evidence reveals that centronuclear myopathy mutations converge upon common cellular dysfunction extending beyond membrane trafficking. This review proposes a unified model positioning CNM as a disorder of impaired organelle communication and structural crosstalk. We focus on how mutations in Myotubularin1 (MTM1) and gain-of-function mutations in Dynamin 2 (DNM2) disrupt the triad architecture, leading to aberrant calcium handling, mitochondrial dysfunction, imbalanced reactive oxygen species (ROS) production, and defective autophagy. These dysfunctions are not isolated but form a pathological feedback loop that compromises muscle integrity and regeneration. By identifying shared mechanisms across CNM types, this review positions the disorder as the convergence of organelle stress and cytoskeletal network failure. This perspective reveals novel therapeutic strategies based on the principle that targeting a central pathological node may alleviate systemic dysfunction. However, given the complexity of the organelle feedback loop, a comprehensive, multi-target approach may ultimately be required to achieve full phenotypic rescue across all affected tissues.

Muscles doi: 10.3390/muscles5020034

Authors: Antonela Karmen Ivišić Dario Vrdoljak Nikola Foretić Vladimir Pavlinović Ivan Drviš

Background: Respiratory muscle strength (RMS) is a critical factor influencing athletic performance, particularly in high-intensity or prolonged activities. RMS encompasses inspiratory (IMs) and expiratory muscles (EMs), which differ in anatomical structure, fiber composition, and responsiveness to training. Methods: This pilot interventional within-subject study investigated the effects of two resistive respiratory muscle training (RMT) protocols on RMS and small airway function in eight physically active adults (two females, six males). Maximal inspiratory (MIP) and expiratory pressures (MEP), along with pulmonary function tests (PFTs), were measured using the Airofit PRO™ device and spirometry before and after two consecutive 7-day training protocols, with a 2-day break between interventions. The workload was progressively increased by lengthening the duration of forced inhalation and exhalation, while keeping the air resistance constant. Results: Results demonstrated significant improvements in MEP across both protocols and after a 10-day washout period (p < 0.001–0.03), whereas MIP showed no significant changes (p = 0.19–0.66). Moderate transient improvements were observed in small airway flow (MEF25%) following the first protocol (ES = 0.62), which regressed after the second. Conclusions: These outcomes suggest differential responsiveness of respiratory muscles to RMT; EMs, characterized by a higher proportion of fast-twitch type II fibers and a predominantly passive role in normal breathing, respond rapidly to short-duration, high-intensity forced expiration training through neuromuscular adaptations. Conversely, IMs, dominated by slow-twitch type I fibers, require longer-duration, higher-load training to elicit meaningful adaptations, explaining the limited changes in MIP. Small airway function appeared minimally trainable due to structural and physiological constraints, with short-term improvements likely reflecting effort-dependent factors rather than lasting adaptations. Finally, RMT can selectively enhance EM performance through appropriately designed short-duration, high-intensity interventions, while IMs may necessitate prolonged or higher-load stimuli. The findings highlight the importance of targeted training strategies, individualized to muscle fiber composition and functional demands, to optimize respiratory performance. Future research should investigate longer interventions, larger diverse cohorts, and precise measurement methods to further elucidate RMT’s effects on both respiratory muscles and small airway function.

Muscles doi: 10.3390/muscles5020033

Authors: Mikyung Ryu

Background/Objectives: Sarcopenia, characterized by progressive loss of skeletal muscle mass and function, is a major public health concern among aging populations. While physical activity is recognized as protective, the comparative effectiveness of different exercise modalities remains understudied in Asian populations. This cross-sectional study investigated the association between exercise type and sarcopenia prevalence among Korean adults aged 40 years and older. Methods: This cross-sectional study analyzed data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2024. A total of 1688 adults aged ≥40 years were included. Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia (AWGS) 2019 criteria, incorporating dual-energy X-ray absorptiometry (DXA)-based appendicular skeletal muscle mass index (ASMI) and handgrip strength. Due to the absence of physical performance measures in this survey cycle, the operational definition required both low ASMI and low handgrip strength. Exercise types were categorized into four groups: no exercise, aerobic only, resistance only, and combined exercise. Multivariable logistic regression, adjusting for age, sex, socioeconomic status, lifestyle factors, nutritional intake, and comorbidities, was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: Sarcopenia prevalence was 13.2% (n = 223). In the fully adjusted model, resistance-only exercise was associated with 56% lower odds of sarcopenia (OR 0.44, 95% CI 0.23–0.82, p = 0.010), and combined exercise with 69% lower odds (OR 0.31, 95% CI 0.13–0.78, p = 0.012). Aerobic-only exercise showed no significant association (OR 0.88, 95% CI 0.54–1.42, p = 0.594). The protective association was statistically significant in the 60–69 age group (OR 0.28, 95% CI 0.11–0.74), with similar but non-significant trends in other age groups. Conclusions: Resistance exercise, either alone or combined with aerobic exercise, is associated with lower odds of sarcopenia in Korean adults aged 40 and older. These observational findings warrant further investigation through prospective and interventional studies before informing public health strategies. Interpretation should consider the limited sample size in the resistance-only subgroup (n = 18 with sarcopenia) and the cross-sectional design, which precludes causal inference.

Muscles doi: 10.3390/muscles5020032

Authors: Bana H. Odeh Amanda L. Wellman Michael Ameye Zachary Atwood Luke Gray Aiswarya Saravanan Havish Poluru Morium Begam Takako I. Jones Renuka Roche Joseph A. Roche

Neuromuscular electrical stimulation (NMES) is integral to studying muscle function in healthy and dystrophic mice. Certain commercial electrodes and laboratory stimulators used for NMES in mice are no longer in production. We developed and/or tested low-cost, open-source alternatives to discontinued commercial standards. We performed two studies—a comparison of electrodes and a comparison of stimulators. In the electrode study, in vivo NMES was applied to the left hindlimb ankle dorsiflexors in healthy C57BL/6J and dysferlin-null BLAJ mice using three electrode types: a previously available commercial electrode, a custom 3D-Printed electrode, and a custom Pen electrode assembled from off-the-shelf components. Twitch and tetanic torque were measured and compared using two-way repeated-measures ANOVA. Twitch torque differed by electrode type (p = 0.031), with lower values observed for the Pen electrode compared with the 3D-Printed electrode (e.g., 573 ± 72 vs. 666 ± 70 mN.mm in C57BL/6J mice), whereas tetanic torque did not differ significantly between electrode types (p = 0.060). In the stimulator study, twitch and tetanic contractions were elicited using the open-source StimJim stimulator and compared with contractions elicited by the discontinued Grass S48 stimulator. Twitch torque was lower with the StimJim (588 ± 107 mN.mm) compared with the Grass S48 (698 ± 116 mN.mm; p < 0.001), whereas tetanic torque values were not statistically different (p = 0.055). These findings indicate that open-source electrodes and stimulators can produce similar maximal tetanic torque under the tested conditions, although differences in twitch torque and stimulation parameters should be considered. These results reflect a methodological validation of accessible tools rather than a formal equivalence analysis.

Muscles doi: 10.3390/muscles5020031

Authors: Miki Yoshimura Takanori Taniguchi Takeshi Yoshitomi Yuki Hashimoto

Stretching of the upper trapezius muscle reduces stiffness and choroidal blood flow velocity, but its effect on skin blood flow remains unclear. We evaluated the changes in upper trapezius skin circulation hemodynamics before/after self-stretching using skin laser speckle flowgraphy (LSFG). Twenty-two healthy young adults (median age [Q1–Q3]: 21.0 [20.0–21.0] years) were enrolled. Trapezius stiffness was assessed using ultrasound strain elastography, and skin and choroidal blood were measured with skin and ocular LSFG, respectively, using mean blur rate (MBR) as an index of blood flow velocity. Intraocular pressure (IOP); systolic (SBP), diastolic (DBP), and mean blood pressure (MBP); heart rate (HR); ocular perfusion pressure (OPP); salivary α-amylase (sAA) activity; and subjective eyestrain/shoulder stiffness symptoms (visual analog scale, VAS) were evaluated at baseline and after stretching. SBP, DBP, MBP, OPP, sAA activity, VAS scores for eyestrain and shoulder stiffness, trapezius stiffness, and skin and choroidal MBR decreased significantly after self-stretching, whereas IOP and HR remained unchanged. Trapezius muscle self-stretching reduces muscle stiffness and induces relaxation in healthy adults, accompanied by reduced sympathetic activity and decreased systemic, choroidal, and local skin circulation. These findings suggest that skin LSFG may serve as a useful, non-invasive tool for evaluating shoulder stiffness.

Muscles doi: 10.3390/muscles5020030

Authors: Anthony B. Trombetta William J. Hanney Abigail W. Anderson Morey J. Kolber

Background: Tensiomyography (TMG) offers a noninvasive means of evaluating skeletal muscle contractile properties, including muscle displacement (Dm), delay time (Td), contraction time (Tc), half-relaxation time (Tr), and sustain time (Ts). When applied to lumbosacral musculature, interpretation may be influenced by changes in muscle stiffness that occur across the respiratory cycle. Understanding these fluctuations is essential for improving measurement consistency and data interpretation. Methods: Thirty healthy young adults (mean ± SD age = 21.07 ± 1.55 years) underwent TMG assessment of the erector spinae (ES) and latissimus dorsi (LD) at four distinct lung volumes: end-tidal inspiratory volume (ETIV), end-tidal expiratory volume (ETEV), total lung capacity (TLC), and residual volume (RV). Visual cues were used to guide participants’ respiratory phases. Paired-samples t-tests compared TMG parameters across respiratory conditions. Results: For the ES, significant differences were observed in Dm, Tr, and Ts between ETIV and ETEV (p ≤ 0.05), ETIV and TLC (p ≤ 0.05), and ETEV and RV (p ≤ 0.05). No statistically significant differences were identified for the LD (p ≥ 0.12). Conclusions: Some erector spinae contractile properties vary across the respiratory cycle, which may affect TMG outcomes. The findings of this research lend belief to the idea that a standardized respiratory phase during data collection may improve the reliability and comparability of TMG measurements involving trunk musculature. Future research could address the negative findings for latissimus dorsi and further determine which muscles require respiratory standardization.

Muscles doi: 10.3390/muscles5020029

Authors: Peter M. Tiidus

Although widely used, massage has not been reported to be effective in enhancing recovery from exercise-induced muscle damage in humans. Studies using massage-like interventions in animal models have, in contrast, consistently demonstrated a significant enhancement of muscle repair, reduction in muscle inflammation and enhanced return of muscle force following muscle damage. The physiology of muscle damage and repair and the putative physiological mechanisms of potential massage-induced muscle repair and post-damage recovery, including soreness sensation, edema, inflammation, protein synthesis and other related mechanisms, are reviewed in this context. Animal models have demonstrated that massage effectiveness in enhancing post-damage muscle repair is dictated by the timing, duration, force and technique of its application and may also be modified by age and sex effects. The potentially very narrow “window of effectiveness” of massage application for the enhancement of post-damage muscle repair in humans has yet to be defined. And the lack of demonstrated effectiveness for massage on post-damage muscle recovery may be due to the wide range and inconsistency of massage techniques, timing and methodologies applied in human studies. Until a specific massage application protocol is defined for massage efficacy in post-damage human muscle recovery, therapists will continue to work blind, using a variety of techniques which lack empirical validity and have an undemonstrated effectiveness for enhancing muscle repair.

Muscles doi: 10.3390/muscles5020028

Authors: Takanori Taniguchi Ryoutarou Mutou Kokoro Oki Miki Yoshimura Yuko Kodama Nao Nakamura Yuki Hashimoto

This study evaluated changes in upper trapezius muscle stiffness and choroidal blood flow velocity before and after ultrasonic therapy of the trapezius muscle. Participants included 27 healthy young adults in their 20 s (median age [Q1–Q3]: 21.0 [19.3–21.0]) without subjective shoulder pain. All participants received a single-session ultrasound intervention, and no control group was included. Intraocular pressure (IOP), systolic blood pressure (BP), diastolic BP, mean BP, heart rate (HR), ocular perfusion pressure (OPP), and salivary α-amylase (sAA) activity, a marker of autonomic nerve function, were assessed at baseline and after therapy. Stiffness of the upper trapezius muscle was evaluated using shear wave elastography, and choroidal hemodynamics were assessed by measuring the mean blur ratio (MBR), a relative index of macular blood flow velocity, using laser speckle flowgraphy. IOP, systolic BP, diastolic BP, mean BP, HR, OPP, sAA activity, and MBR reduced significantly after therapy. The shear elastic modulus of the trapezius muscle also decreased significantly. However, no significant correlations were observed among the parameters. Among healthy adults in their 20 s without shoulder pain, trapezius muscle ultrasound therapy may enhance parasympathetic activity, contributing to decreases in systemic and choroidal circulatory parameters. These findings indicate that ultrasound therapy for shoulder stiffness may influence local musculoskeletal characteristics, systemic and ocular circulation, and autonomic pathways.

Muscles doi: 10.3390/muscles5020027

Authors: Consolato Gullì Giuseppe Ferrara Emanuele Ferravante Roberto Calbi Mario Di Diego Davide Parisi Daniele Perla Tommaso Villa Luigi Natale

Myositis ossificans (MO) is a benign, self-limiting heterotopic ossification process that typically develops within soft tissues following trauma, although non-traumatic forms have also been described. Despite its benign nature, MO frequently represents a diagnostic challenge, particularly in its early stages when imaging findings may mimic aggressive soft-tissue tumors, leading to unnecessary biopsies or surgical interventions. This narrative review provides an updated overview of the classification, pathophysiology, and imaging features of myositis ossificans, with a specific focus on the time-dependent evolution of radiologic appearances across different imaging modalities. Radiologic findings are discussed according to disease stage, highlighting key diagnostic clues such as the zonal phenomenon and peripheral maturation pattern. In addition, the main entities included in the differential diagnosis are reviewed, with particular emphasis on imaging features that help distinguish myositis ossificans from soft-tissue sarcomas and other calcified or ossified lesions. Finally, current management strategies and the role of imaging in patient follow-up are summarized. A thorough understanding of the evolving imaging spectrum of myositis ossificans is essential for radiologists and clinicians to achieve an accurate diagnosis, guide appropriate management, and avoid overtreatment.

Muscles doi: 10.3390/muscles5020026

Authors: Sam J. Hillen Matthew D. Fliss Cameron J. Mitchell

Dynamic muscular endurance, the ability to lift a submaximal load until task failure, is a common measure in both cross-sectional and training studies. However, the repeatability of low-load muscular endurance in the knee extensors has not been well established. Establishing reliability metrics is essential to ensure that observed differences reflect true physiological changes rather than measurement error. The purpose of this study was to quantify the repeatability of low-load dynamic knee extensions performed to task failure. Forty healthy adults completed three visits, each consisting of one set of knee extensions at 20%, 30%, and 40% of one repetition maximum (1RM) to assess relative muscular endurance, and three sets at 20% 1RM on the contralateral leg to assess the impact of fatigue within a single session (fatigue curve). Intraclass correlation coefficients (ICCs), standard error of the measurement, and smallest detectable difference (SDD) were calculated. Repeatability ranged from moderate to excellent across conditions (ICC = 0.77–0.94). Lower loads and later sets demonstrated reduced repeatability compared with heavier loads and earlier sets. These results indicate that researchers and practitioners should consider load and fatigue curve effects in protocol design and SDDs when interpreting the meaningfulness of individual changes in knee extension muscular endurance.

Muscles doi: 10.3390/muscles5020025

Authors: Sabine D. Brookman-May

Physical exercise can influence cognitive performance and neurobiological processes, but evidence spans diverse modalities, intensities, and adult populations. Acute exercise represents a state of transient skeletal muscle activation that induces systemic signaling through metabolic, endocrine, and myokine-mediated pathways, which may contribute to neurocognitive modulation. To map the breadth of acute exercise–cognition research, characterize cognitive and biological outcomes, and identify consistent patterns and gaps. Studies of adults (≥18 years) involving a single exercise session or short microcycle (≤7 days) with pre–post assessment of cognition and/or neurobiological markers across any exercise modality (aerobic, resistance, high-intensity interval training/HIIT, combined, vibration, mind–body) were included. PubMed and CENTRAL were systematically searched, yielding 101 studies. Data were extracted using a structured framework capturing exercise modality, dose, cognitive domains, biomarkers, neuroimaging outcomes, population characteristics, and study design features. Most studies examined young adults (53%) or older adults (32%). Aerobic exercise predominated (62%), followed by resistance (18%) and combined modalities (12%). Moderate-to-vigorous aerobic exercise consistently improved executive function, processing speed, and working memory. Resistance exercise also enhanced executive function in several trials (31 studies). Neurobiological correlates included increases in Brain-Derived Neurotrophic Factor (BDNF), lactate, catecholamines, and prefrontal activation, though variability in sampling limited mechanistic conclusions. Acute exercise is consistently associated with improvements in executive function and processing speed across modalities. Standardized exercise protocols, biomarker timing, and cognitive assessments are needed to strengthen mechanistic synthesis.

Muscles doi: 10.3390/muscles5020023

Authors: David Ayi-Bonte Samantha Dworacek James Madden Jacob Evans Ingrid E. Lofgren Kathleen J. Melanson Christie L. Ward-Ritacco Marie Mortreux

NASA intends to return humans to the Moon, where partial gravity will put them at risk of musculoskeletal deconditioning. Resveratrol (RSV) is a promising nutritional countermeasure that may protect muscle health during disuse; however, its efficacy and mechanism in simulated lunar gravity are unknown. Forty adult male Wistar rats underwent 14 days of normal loading or partial weight-bearing at 20% of normal loading (PWB20). Unloaded animals received daily RSV supplementation with or without an ERα antagonist to test whether ERα was required to mediate RSV benefits. Muscle function was longitudinally assessed, and a Western blot was used to quantify key signaling proteins in the soleus muscle. PWB20 led to a significant reduction in grip strength (−14.2%) associated with marked changes in electrophysiological muscle properties. RSV-supplemented animals performed better throughout the study, but not when Erα was inhibited. RSV supplementation resulted in a greater ERα phosphorylation ratio compared to PWB20 alone (3.5 vs. 1.91). These results suggest that RSV can mitigate muscle deconditioning in a lunar gravity analog and that ERα signaling is required.

Muscles doi: 10.3390/muscles5020024

Authors: Ivan Curovic Milan Markovic Lazar Toskic Jill Alexander Damian J. Harper

(1) Background: Handgrip strength (HGS) is a widely used indicator of neuromuscular function, with predictive values for health and performance outcomes. The aim of this study was to evaluate the intraday and interday reliability of maximal and explosive handgrip force–time metrics using the Kinvent K-Grip handheld dynamometer. (2) Methods: Thirty-four participants performed three maximal voluntary isometric contractions per hand across two testing days. Force–time data were analysed for peak force (PF), mean force (MF), peak rate of force development (RFD), time-specific RFD, impulse, and forces at fixed time points. Reliability was assessed using intraclass correlation coefficients (ICCs), standard error of measurement (SEM), minimal detectable change (MDC), and coefficient of variation (CV%). (3) Results: The device demonstrated excellent relative and absolute reliability for PF and MF across both days (ICC > 0.97; CV < 6%; MDC ≈ 5 kg). Later-phase explosive metrics (F250 and Imp200) showed good-to-excellent relative reliability (ICC = 0.88-0.99; CV = 4–14%), although with variable absolute reliability (MDC F250 ≈ 4–8 kg, MDC Imp200 ≈ 1 kg·s). For early-phase metrics, relative reliability was only moderate to good (ICC = 0.67–0.88) and characterised by a high degree of variability (CV = 15–22%). (4) Conclusions: The K-Grip handheld dynamometer is a reliable tool for cross-sectional assessments and for tracking larger maximal strength and later-phase force improvements at fixed time points. Early-phase explosive metrics are less suitable for monitoring intervention effects due to high measurement error and fatigue sensitivity.

Muscles doi: 10.3390/muscles5020022

Authors: Toshiaki Soga Taspol Keerasomboon Parunchaya Jamkrajang Norikazu Hirose

Research has yet to investigate the effects of unilateral Nordic hamstring training with a sloped platform (UNHT) on the fascicle length of the biceps femoris long head (BFlh FL) in previously injured legs. This study aimed to address this gap. A longitudinal pre–post design without a control group was used to examine the effects of 6 weeks of UNHT in eight young male athletes with a history of hamstring strain injury (HSI). Pre- and post-training measurements of middle and distal BFlh FL in the injured and uninjured legs were obtained using ultrasonography. At baseline, middle BFlh FL was significantly shorter in the injured leg than in the uninjured leg (86.0 ± 9.0 mm vs. 99.9 ± 7.6 mm, p < 0.001). Following UNHT, middle BFlh FL significantly increased in both the injured (105.8 ± 9.4 mm, p = 0.001) and uninjured legs (108.0 ± 10.3 mm, p = 0.596). Distal BFlh FL significantly increased in the injured leg (72.4 ± 7.1 mm to 85.7 ± 8.0 mm, p = 0.012), whereas the uninjured leg showed a smaller, non-significant change (72.8 ± 5.5 mm to 79.1 ± 7.5 mm, p = 0.069). These findings demonstrate that UNHT increased BFlh FL in previously injured legs. Because shorter BFlh FL and reduced eccentric strength are established risk factors for HSI, these adaptations may have implications for risk reduction; however, recurrence prevention was not assessed in this study.

Muscles doi: 10.3390/muscles5010021

Authors: Maria Tozzo Pesco Gülru Zeynep Öztürk Shivkumar C. Bhadola Stephen M. Chrzanowski Liubov V. Gushchina Eleonora S. D’Ambrosio

Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular disorder caused by loss-of-function mutations in the dystrophin gene, leading to progressive muscle degeneration, motor decline, respiratory compromise, and cardiomyopathy. Diagnosis typically occurs in early childhood following recognition of motor delays, markedly elevated creatine kinase, and confirmatory genetic testing. Over the past decade, the therapeutic landscape for DMD has expanded substantially, evolving from exclusively supportive care to patient-centric multifaceted treatment paradigms, including corticosteroids, mutation-specific therapies, small molecule disease-modifying approaches, and gene replacement strategies. Despite these advances, no currently available therapy restores full-length dystrophin or completely halts disease progression. This review provides a clinically oriented comprehensive overview of currently Food and Drug Administration (FDA)-approved medications for DMD, with particular emphasis on corticosteroids, exon-skipping therapies, nonsense mutation readthrough agents, recently approved gene therapy, and select ongoing gene therapy trials. We summarize mechanisms of action, clinical efficacy, safety considerations, regulatory status, and highlight the challenges of integrating these therapies into longitudinal care. Through illustrative clinical vignettes, we highlight the real-world complexity of treatment selection, shared decision-making, and longitudinal care planning in contemporary DMD management.

Muscles doi: 10.3390/muscles5010020

Authors: Benjamin T. Baker Rebecca E. Rifkin Becka Klein Brittani Lopez Remigiusz M. Grzeskowiak Elizabeth Croy Xiaojuan Zhu Pierre-Yves Mulon David E. Anderson Dustin L. Crouch

Major orthopedic limb surgery is often accompanied by external coaptation; the combined effect of these interventions can lead to muscle atrophy and functional impairment. Large animal models, including goats, are commonly used to study orthopedic interventions, yet longitudinal data on muscle changes after such interventions are limited. This study quantified gastrocnemius muscle adaptations in adult Boer-cross goats undergoing a clinically representative unilateral tibial segmental ostectomy and external coaptation protocol. Muscles on the operated side exhibited statistically significant decreases in mass, length, optimal fiber length, and CSA, and increases in nucleus density compared to muscles on the contralateral, non-operated side (p < 0.05). Although muscle properties showed partial recovery over time, mass and CSA remained 20–30% lower on the operated side than on the non-operated side at 12 months post-surgery despite cast removal at about 2 months post-surgery. Muscle CSA was positively correlated with bone mineral density and peak vertical ground reaction forces measured during the in vivo study. The extent of muscle recovery in the goat model was less than that observed for other mammalian models of hindlimb remobilization. More research is needed to understand the complex interaction between surgery, external coaptation, and muscle properties in the goat model.

Muscles doi: 10.3390/muscles5010019

Authors: Anne-Laure Charles Liliane Tetsi Giulia Quiring Cindy Barnig Margherita Giannini Alain Meyer Anne Lejay Claire Lugnier Bernard Geny

Peripheral arterial disease is a leading cause of amputation and/or death worldwide. Phosphodiesterase 4 (PDE 4) inhibitors demonstrated beneficial effects in ischemia–reperfusion (IR) settings, but whether PDE 4 inhibition protects skeletal muscle against IR deleterious effects is unknown. We therefore performed limb IR (two hours each) in twenty-one male Swiss mice (12–16-week-old) treated or not with Rolipram (1 mg/kg i.p. 30 min before ischemia and 5 min before reperfusion). The muscles were analyzed 4 h after the onset of ischemia. IR significantly increased leucocyte infiltration (93.13 ± 6.886 vs. 150.1 ± 18.38 cells/mg of muscle, p < 0.05) and apoptosis (Bax/Bcl2 ratio, +239%, p < 0.05), together with enhanced mitochondrial fission transcripts (+224% for Drp1, p < 0.01 and +368%, p < 0.0001 for Fis1), and decreased mitochondrial respiration and antioxidant defense. PDE 4 inhibition reduced leucocyte infiltration (150.1 ± 18.38 vs. 55.58 ± 13.83; p < 0.01) and apoptosis (+67%, NS) in association with reduced fission markers (+91% for Drp 1 and +111%, p < 0.05, for Fis 1). Muscle mitochondrial respiration did not improve. In conclusion, PDE 4 inhibition using Rolipram partly protected skeletal muscles against IR-induced deleterious effects. These data support further studies investigating the usefulness of leucocytes modulation in lower-limb IR and a potential beneficial effect of PDE 4 inhibition in peripheral arterial disease.

Muscles doi: 10.3390/muscles5010018

Authors: Konstantina Intziegianni Epifanios Katsamis Marcos Michaelides Koulla Parpa

Studies examining the electromyographic activation of pectoralis major (PM) and triceps brachii (TB) muscles during push-ups of varied hand positions are limited, and findings are inconsistent. The aim was to investigate the electromyographic activation of PM and TB during standard, diamond, and wide hand position push-ups. Twenty young males performed six repetitions of each push-up variation while the electrical activity of PM and TB was recorded, averaged, and normalized to the peak root mean square (RMS) across repetitions for each push-up. RMS (mV) and normalized RMS (%) were calculated for each muscle, push-up variation, and contraction phase (eccentric/concentric). Two separate three-way ANOVAs with Bonferroni post hoc correction were used (α = 0.05). TB demonstrated statistically significantly higher RMS (mV) and normalized RMS (%) than PM (p < 0.05), in diamond, followed by standard and wide push-ups. A statistically significant higher activation of RMS (mV) was observed in concentric compared to eccentric (p < 0.05); however, after normalizing RMS (%), contraction phase had no effect (p > 0.05) and there was no significant three-way interaction (p > 0.05). Diamond push-ups elicited the highest relative activation for both the PM and TB. Normalized RMS revealed the consistency of muscle effort in both contraction phases, sustaining near-maximal activation regardless of hand position. These findings support adaptable training strategies, with potential applications in rehabilitation and strength training contexts.

Muscles doi: 10.3390/muscles5010017

Authors: Elena Caso-Fontánez Pablo López-Sierra Carlos D. Gómez-Carmona Sergio J. Ibáñez Diego Muñoz

Background: The relationships between segmental body composition and multidimensional performance outcomes remain insufficiently characterized in adults with limited but regular physical activity. This study examined associations between body composition parameters and functional test performance, while identifying sex-based differences. Methods: Forty-seven adults (31 women, 16 men; age 48.04 ± 11.33 years) underwent segmental bioelectrical impedance analysis and functional assessments including handgrip strength, isometric plank endurance, and single-leg balance. Correlations and sex comparisons statistical tests were performed. Results: Strong positive correlations were observed between segmental muscle mass and handgrip strength (r = 0.74–0.84, p < 0.05), with moderate associations for plank endurance (r = 0.30–0.32, p < 0.05). Fat mass demonstrated inverse relationships with performance, particularly for plank endurance (r = −0.36 to −0.62, p < 0.05). Males exhibited significantly greater muscle mass (p < 0.01), superior handgrip strength (p < 0.01), and longer plank times (p = 0.01). Females presented higher fat mass in lower limbs (p < 0.01). Conclusions: Segmental muscle mass shows strong associations with strength and moderate associations with core endurance, while adipose tissue exhibits inverse relationships. Pronounced sexual dimorphism exists in both body composition and functional capacity.

Muscles doi: 10.3390/muscles5010016

Authors: Giulia Bongiorno Nicole Salvador Samuele De Cecco Helena Biancuzzi Francesca Dal Mas Chiara Pinzini Luca Miceli

Background: The aim of this observational preliminary study is to detect any changes in body mass, muscle strength and characteristics of the pectoralis major muscle in women who have undergone breast surgery treatments. Methods: Instrumental assessments, completed before surgery and after 60 and 120 days, included sonoelastography, dynamometric examination and surface electromyography (sEMG) of the pectoralis major muscle, hand grip test, body bioimpedance analysis; the DASH (Disability of the Arm, Shoulder and Hand) questionnaire and pain assessment using the NRS (Numerical Rating Scale). Results: An initial increase in weight and fat mass was observed, followed by a reduction related to the resumption of physical activity stimulated by physiotherapy and medical support. The IC (intracellular)/EC (extracellular) ratio showed an increase in extracellular fluids in the final phase, indicative of possible water retention and early oedema. Muscle strength and DASH scores showed a functional decline, which may be explained by reduced physical activity and the direct involvement of the pectoral muscle in surgical and radiotherapy procedures. Sonoelastography showed color variations suggestive of changes in tissue stiffness, useful for distinguishing between reinforcement processes and possible scarring. Conclusions: This multidimensional approach can be useful in the early monitoring of some tissue alterations (i.e., fat mass) as an aid to define personalized rehabilitation protocols for women who have undergone breast surgery.

Muscles doi: 10.3390/muscles5010015

Authors: Hash Brown Taha Nathan Robbins Firas-Shah Zoha Shirley Zhu Nandhana Vivek Aleksander Bogoniewski

Animal and human studies show that exercise induces organism-wide molecular adaptations that are partly mediated by exerkines which are secreted factors that enable inter-organ communication between tissues such as skeletal muscle, adipose tissue, liver and the brain. However, the tissue-specific responsiveness of individual exerkines and how these responses differ across species, exercise conditions and sexes remain poorly understood. To address this gap, we systematically analyzed skeletal muscle transcriptomic responses of 40 exerkines using three publicly available datasets including MetaMEx, Extrameta and the MoTrPAC 6-month-old rat training dataset. We reviewed exerkine-specific regulation in humans, mice and rats across acute and chronic exercise and inactivity. We determined conserved, non-conserved, and discordant exerkines across species and whether they were dependent on exercise modality or sex. Our review reveals substantial heterogeneity in skeletal muscle transcriptomic exerkine regulation with only a small subset showing conserved changes across species. Additionally, a key limitation is that our analysis was limited to transcriptomic data and may not reflect protein-level abundance, secretion, or uptake by recipient tissues. Therefore, we highlight a need for multi species and multi condition approaches when selecting exerkines as biomarkers or surrogate therapeutic targets.

Muscles doi: 10.3390/muscles5010014

Authors: Anna Christakou George Plakoutsis Athanasios Gkagkalis Eleftherios Paraskevopoulos

Objectives: Medial tibial stress syndrome (MTSS) is a common overuse injury among athletes, yet limited evidence exists regarding muscle-specific deficits. This study aimed to (a) examine differences in gastrocnemius and soleus strength and endurance between the affected and healthy lower limb, and (b) investigate the relationships between gastrocnemius and soleus strength, endurance, and pain intensity in athletes with MTSS. Methods: Thirty athletes aged 18–40 years with MRI-confirmed MTSS, who had completed a standardized physiotherapy program, underwent isometric dynamometry and heel-rise endurance testing under knee-extended (gastrocnemius) and knee-flexed (soleus) conditions. Relative strength values and heel-rise repetitions were compared between limbs using paired t-tests. Correlations and regression analyses were performed between pain intensity, strength, and endurance of the affected limb using Pearson’s r and simple linear regression. Results: Significant deficits were found in both muscles of the affected limb, with reduced isometric strength and fewer heel-rise repetitions (gastrocnemius heel-rise: t(29) = −6.47, p < 0.001; gastrocnemius strength: t(29) = −6.27, p < 0.001; soleus heel-rise: t(29) = −5.37, p < 0.001; soleus strength: t(29) = −4.87, p < 0.001). Strong positive correlations were observed between muscle strength and endurance, while higher pain intensity was negatively associated with gastrocnemius performance. Moreover, pain intensity significantly predicted gastrocnemius strength (F(1,28) = 5.90, p = 0.022, R2 = 0.17) and endurance (F(1,28) = 7.56, p = 0.009, R2 = 0.22), but not soleus function. Physiotherapy duration, number of physiotherapy sessions, and self-reported pain improvement were not significant predictors to either soleus or gastrocnemius endurance, only training frequency emerging as the only independent variable. Conclusions: Athletes with MTSS exhibited notable impairments in plantarflexor function. These findings underscore the importance of targeted strength and endurance interventions for both the gastrocnemius and soleus muscles to optimize recovery, enhance load tolerance, and reduce recurrence risk. Future research should include pre- and post-rehabilitation assessments, larger sample sizes, and sport-specific cohorts.

Muscles doi: 10.3390/muscles5010013

Authors: Sathish Kumar Gunasekaran Mandam Amzad Khan Mehwish Mirza Santhosh Shanthi Bhupathi Mohamed Sheik Tharik Abdul Azeeze

Skeletal muscle atrophy emerges from intertwined neuromuscular and metabolic failures, in which neuromuscular junction destabilization, excitation contraction coupling defects, and mitochondrial dysfunction collectively intensify calcium dysregulation and drive the accumulation of reactive oxygen and nitrogen species (RONS), reinforcing proteolytic and catabolic signaling programs. To integrate recent evidence on the neuromuscular redox interface and highlight therapeutic strategies that target these interdependent drivers of atrophy. RONS-mediated activation of NF-κB and FOXO pathways accelerates ubiquitin proteasome and autophagy lysosome degradation, leading to motor unit loss. Stem cell therapies (satellite cells, MSCs, and iPSC progenitors) seek to restore regenerative potential but face hurdles in engraftment and reinnervation. Gene-based interventions, including antioxidant gene delivery, Nrf2 activation, RNA modulators, and CRISPR editing, offer new avenues but remain limited by safety and delivery barriers. Bioengineering platforms such as hydrogels, decellularized scaffolds, and extracellular vesicles provide architectural, trophic, and immunomodulatory support. Translational progress requires rigorous safety pipelines, mechanistic biomarkers of motor unit recovery, and modular combination regimens that integrate cells, genes, scaffolds, and rehabilitative input. By aligning neuromuscular biology with redox control, emerging strategies hold promise to rebuild innervated, fatigue-resistant muscle across acquired and genetic atrophy syndromes.

Muscles doi: 10.3390/muscles5010012

Authors: Stuart Evans

Tourette Syndrome (TS) is a neurodevelopmental disorder depicted by the occurrence of tics and accompanying behavioral problems that commonly appear during childhood. Tics, both motor and vocal, may cause musculoskeletal pain. Both acute and chronic muscle pain have been recognized as a common comorbid aspect of TS-related tic disorders in childhood. The pain most reported in children includes cervical, throat, shoulder, ocular, and joint pain, with most children reporting musculoskeletal pain in more than one part of the body. The impact of muscular pain caused by motor and phonic tics can negatively affect a child’s quality of life. This review describes the association and causation of musculoskeletal pain in childhood tics and TS, which are commonly under recognized and diagnosed. An analysis of the presence of musculoskeletal pain, the severity of the pain, the location of the pain and the movement incapacity due to pain in children is reviewed. Pharmacological and non-pharmacological interventions known to improve musculoskeletal pain in children are highlighted with supportive frameworks evaluated. Further research is needed to better understand musculoskeletal pain cause(s) and prevalence along with age-appropriate assessment methods and outcomes measures. Motor- and phonic-related musculoskeletal pain should be recognized as a common comorbid characteristics of TS and tic disorders in childhood. Such recognition may lead to greater therapeutic opportunities for this problematic condition.

Muscles doi: 10.3390/muscles5010011

Authors: Ioannis Stathas Nikos Koundourakis Charalampos Christoforidis George Kouvidis Anna Christakou

Objectives: This clinical commentary presents a four-pillar rehabilitation framework implemented in the elite football setting of OFI Crete FC and designed to facilitate the return of football players to training and competitive play. The framework is structured around five core components: (a) effective load management during training and matches, (b) individualized rehabilitation programs and injury prevention strategies integrated within the recovery phase, (c) a novel on-field rehabilitation framework, and (d) an extended secondary prevention plan. Methods: This comprehensive approach was implemented over a three-year period with the OFI Crete FC football team and involved 87 elite professional players between the ages of 17 and 35. Throughout this time, 180 injuries were documented, ranging from mild to severe injuries. Results: The outcome illustrated that only 40% of these injuries led to players missing official matches, while the recurrence or follow-up injury rate was limited to just 10%. Over the course of the three years, a steady 60% decline in injury rates was observed. Conclusions: These findings emphasize the crucial importance of training load management, the integration of injury prevention strategies throughout the rehabilitation process, and the early initiation of on-field rehabilitation. Within the clinical setting of OFI Crete FC, the implementation of this integrated rehabilitation framework was associated with favorable observations in injury incidence, player absence days, and return-to-play timelines, which may reflect that the approach has potential benefits while remaining observational in nature.

Muscles doi: 10.3390/muscles5010010

Authors: Rishabh Rege Kristin M. Mendez Riya Patel Sydnie Keane Kevin K. McCully

Neuromuscular electrical stimulation (NMES) has been shown to provide health benefits similar to those of exercise. The aim of this study was to quantify the acute physiological effects of multiple muscle stimulation on the whole body and individual muscles. Nine healthy young adults were tested. NMES of eight muscle groups was performed with NMES stimulators. The vastus lateralis, biceps femoris, medial gastrocnemius, and tibialis anterior muscles of both legs were stimulated for ten minutes with twitch stimulations at the highest comfortable stimulation current. Whole-body metabolism was measured using a metabolic cart. A finger pulse oximeter and a tri-axial accelerometer were used to measure heart rate and muscle fatigue, respectively. Muscle metabolism (mVO2) was measured using near-infrared spectroscopy (NIRS) during short periods of ischemia. Femoral artery blood flow was measured using Doppler ultrasound. Whole-body VO2 and heart rate increased moderately by 36% and 22%, respectively, after 10 min of NMES. NMES increased mVO2 by 12-fold higher than resting on average, with the gastrocnemius having the smallest increase and the vastus lateralis having the greatest increase. Peak diastolic blood flow velocity was significantly reduced by 50% after 10 min of NMES. Simultaneous lower-body NMES moderately improved whole-body metabolism, muscle metabolism, and blood flow, increasing our understanding of the beneficial effects of NMES.

Muscles doi: 10.3390/muscles5010009

Authors: Isabel García-Valiente Francisco Pradas Miguel Ángel Ortega-Zayas Carlos Castellar-Otín Alejandro García-Giménez Miguel Lecina

Background: Trail running (TR) is an endurance discipline characterized by prolonged exercise, irregular terrain, and marked elevation changes, which increase eccentric muscular load and may induce muscular, neuromuscular, and cardiac damage. Objective: This study aimed to systematically review the evidence on muscular, neuromuscular, and cardiac damage associated with TR participation. Methods: This systematic review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD420251135043). Five databases (PubMed, Web of Science, Scopus, SportDiscus, and ScienceDirect) were searched up to 31 August 2025. Observational, longitudinal, prospective, and case studies involving healthy adolescent or adult trail runners were included. Outcomes comprised muscle damage biomarkers (e.g., creatine kinase, alanine aminotransferase), neuromuscular function (e.g., squat jump performance, maximal voluntary isometric contraction), and cardiac biomarkers (e.g., CK-MB, cardiac troponins, NT-proBNP). Methodological quality was assessed using the National Heart, Lung, and Blood Institute Study Quality Assessment Tool. Results were synthesized qualitatively. Results: Fifteen studies met the inclusion criteria, including a total of 247 participants. Post-race analyses consistently showed marked increases in muscle damage biomarkers and significant reductions in neuromuscular performance. Transient elevations in cardiac biomarkers were also observed, suggesting acute but reversible cardiac stress following TR events. Limitations: Evidence was limited by methodological heterogeneity, small sample sizes, and underrepresentation of female athletes. Conclusions: It was found that trail running induces substantial acute muscular, neuromuscular, and cardiac stress, particularly in events with high eccentric loading. Monitoring biochemical and neuromuscular markers may support training load optimization, recovery strategies, and injury prevention.

Muscles doi: 10.3390/muscles5010008

Authors: Justin S. Pioske Jocelyn E. Arnett Dolores G. Ortega Trevor D. Roberts Robert W. Smith Tyler J. Neltner Richard J. Schmidt Terry J. Housh

This study: (1) Determined the time course of early-phase adaptations in average peak torque (APT), the rate of velocity development (RVD), and average power (AP) following very short-term unilateral, reciprocal, concentric isokinetic forearm extension and flexion training in untrained women; and (2) determine whether training the non-dominant arm induced cross-education adaptations in the dominant, non-trained arm. Twelve untrained women (age: 21.7 ± 1.2 yrs) completed four testing and four training visits (pre-test and following 2, 3, and 4 days of training). The testing consisted of three maximal repetitions of the dominant and non-dominant arms at 60°, 180°, and 300°·s−1, with APT and AP calculated as the average of the 3 repetitions and RVD as the fastest repetition. The training consisted of 6 sets of 10 maximal repetitions at 180°·s−1 with the non-dominant arm. The differences in mean values across testing visits for APT, AP, and RVD were determined by separate 2 (Arm) × 2 (Muscle Action) × 3 (Velocity) × 4 (Time [across all testing visits]) repeated measures ANOVA (α ≤ 0.05) with Bonferroni-corrected post hoc comparisons. For the trained arm, there were increases in APT (p < 0.001) following four training visits and AP following three (p = 0.006) and four (p = 0.004) training visits. Furthermore, following four training visits, RVD (collapsed across Arms and Muscle Action) decreased at 180°·s−1 (p = 0.002) and 300°·s−1 (p = 0.005) following four training visits. There were no changes in APT or AP (p = 0.155–1.000) in the non-trained arm, which indicated no cross-education adaptations. These findings suggested that 3–4 days of moderate-velocity, unilateral, reciprocal, isokinetic training elicited early-phase adaptations for APT, RVD, and AP in untrained women, while cross-education adaptations for APT and AP were not observed within this timeframe.

Muscles doi: 10.3390/muscles5010007

Authors: Giacomo Papotto Ignazio Prestianni Enrica Rosalia Cuffaro Alessio Ferrara Marco Ganci Calogero Cicio Alessandro Pietropaolo Marco Montemagno Saverio Comitini Antonio Kory Rocco Ortuso

Background: The global increase in orthopedic implant use—both for trauma fixation and arthroplasty—has profoundly transformed musculoskeletal surgery. As a consequence, fractures occurring in the presence of implants have become more frequent and clinically relevant. Yet, these injuries are currently described using highly heterogeneous terminology, including periprosthetic (fracture occurring in the presence of a prosthetic joint replacement) peri-implant (fracture occurring around an osteosynthesis or fixation device), implant-related, and hardware-related fractures (umbrella terms encompassing both prosthetic and fixation devices, used descriptively rather than classificatorily). This coexistence of multiple, context-specific terminologies hinders clinical communication, complicates registry documentation, and limits research comparability across orthopedic subspecialties. Because fractures occurring in the presence of orthopedic implants significantly alter load transfer, muscle force distribution, and musculoskeletal biomechanics, a clear and unified terminology is also relevant for muscle-focused research addressing implant–tissue interaction and functional recovery. Objective: This systematic review aimed to critically analyze the terminology used to describe fractures influenced by orthopedic implants, quantify the heterogeneity of current usage across anatomical regions and publication periods, and explore the rationale for adopting a unified umbrella term—“artificial fracture.” Methods: A systematic search was performed in PubMed, Scopus, and Web of Science from January 2000 to December 2024, following PRISMA guidelines. Eligible studies included clinical investigations, reviews, registry analyses, and consensus statements explicitly employing or discussing terminology related to implant-associated fractures. Data were extracted on publication characteristics, anatomical site, terminology employed, and classification systems used. Quantitative bibliometric and qualitative thematic analyses were conducted to assess frequency patterns and conceptual trends. Results: Of 1142 records identified, 184 studies met the inclusion criteria. The most frequent descriptor in the literature was periprosthetic fracture (68%), reflecting its predominance in arthroplasty-focused studies, whereas broader and more practical terms such as implant-related and peri-implant fracture were more commonly used in musculoskeletal and fixation-related research. Terminological preferences varied according to anatomical site and implant type, and no universally accepted, cross-anatomical terminology was identified despite multiple consensus efforts. Discussion and Conclusions: The findings highlight persistent heterogeneity in terminology describing fractures influenced by orthopedic implants. A transversal, descriptive framework may facilitate communication across subspecialties and support registry-level harmonization. Beyond orthopedic traumatology, this approach may also benefit muscle and musculoskeletal research by enabling more consistent interpretation of data related to muscle–bone–implant interactions, rehabilitation strategies, and biomechanical adaptation.

Muscles doi: 10.3390/muscles5010006

Authors: W. Aline Ingelson-Filpula Karen L. Kadamani Mohammad Ojaghi Matthew E. Pamenter Kenneth B. Storey

(1) Background: The naked mole-rat (Heterocephalus glaber) survives hypoxia–reoxygenation stresses by utilizing metabolic rate depression, achieved in part by downregulating nonessential genes and processes to conserve endogenous cellular resources and prevent buildup of toxic waste byproducts. Tight molecular control of protein degradation (specifically the ubiquitin–proteasome system) is a potent regulatory tool for maintaining muscle integrity during hypoxia, but how this system is regulated in the heart of hypoxia-tolerant species is poorly understood. (2) Methods: The protein expression levels of cullin-RING E3 ligases (specifically CRL4 architecture), deubiquitinating enzymes, and proteasomal activity were assayed in cardiac tissues from H. glaber exposed to 24 h of normoxia or hypoxia in vivo. (3) Results: Overall, the protein expression of E3 ligases decreased, whereas expression of deubiquitinating enzymes increased during hypoxia, all of which play roles in themes of oxidative stress, heightened DNA damage repair, and the HIF-1-VHL-NFκB axis. Proteasomal activity was elevated during hypoxia, which conceivably links to the oxidative stress theory of aging and longevity of H. glaber. (4) Conclusions: Taken together, our results expand current research into protein degradation and extreme environmental stress responses, with a specific focus on cardiac mechanisms related to oxidative stress resistance along the hypoxia-longevity axis.

Muscles doi: 10.3390/muscles5010005

Authors: Flávio Ventura Filipe Maia Ricardo Maia Ferreira Nuno Pimenta Ricardo Pimenta

Muscular strength plays a crucial role in sports performance and is often evaluated using vertical jump tests such as the Squat Jump (SJ) and Countermovement Jump (CMJ). Measurements based on flight time (FT) assume that takeoff and landing postures are identical, yet differences in ankle position can introduce systematic errors. This study examined whether dorsiflexion (DF) or plantarflexion (PF) of the ankle during the flight phase affects jump height. Forty-three active university students completed four repetitions each of SJ and CMJ under DF and PF across two sessions. Jump heights were recorded using a Chronojump-Boscosystem platform. No significant difference was observed in SJ between DF and PF, while CMJ heights were consistently higher under DF (DF: 28.29 cm ± 7.7 cm vs. PF: 27.08 cm ± 7.03 cm, p = 0.001; d = 0.16). Notably, the effect of DF appeared more pronounced in CMJ, suggesting that higher jumps are more sensitive to postural variations. These findings could suggest that DF can artificially increase jump heights as measured on a jump platform, without reflecting true improvements in force production. Coaches and practitioners should interpret FT-derived data with caution, particularly for higher jumps. Future research combining precise motion capture with force platforms could directly track center-of-mass changes and validate this mechanism.

Muscles doi: 10.3390/muscles5010004

Authors: Gabriel J. Sanders Maura Bennett Roger O. Kollock Corey A. Peacock

Background: The study examined sex differences in countermovement jump (CMJ) force plate metrics and neuromuscular responses to a standardized dynamic warm-up in physically active college students. Methods: Forty-one participants (21 males, 20 females) completed pre- and post-warm-up assessments of CMJ performance using a dual force plate system. Body composition was measured via bioelectrical impedance analysis, and performance metrics included force, velocity, power, and other jump metrics. Percent change scores were calculated for all metrics. Results: Males demonstrated significantly greater improvements in braking force metrics compared to females, including force at minimum displacement (11.4% Δ male vs. 5.7% Δ female, p = 0.043), average braking force (10.6% Δ male vs. 5.0% Δ female, p = 0.043), and peak braking force (11.5% Δ male vs. 5.7% Δ female, p = 0.043). No significant sex differences were found in velocity, power, propulsive force, or other general CMJ performance variables. Hierarchical regression analyses revealed that sex was a significant (p ≤ 0.043 for all) predictor of changes in braking force metrics, while lean body mass did not enhance model fit or independently predict force changes. The addition of lean body mass slightly attenuated the sex effect but did not contribute meaningfully to the models. Conclusions: Findings suggest males may experience greater braking force adaptation to a dynamic warm-up, while other performance outcomes appear similar between sexes. These results may inform sex-specific warm-up strategies targeting neuromuscular readiness and braking force development.

Muscles doi: 10.3390/muscles5010003

Authors: Mikal Thrones Thomas Rawliuk Dean M. Cordingley Stephen M. Cornish

Background: The myokine response to various types of exercise may differ and influence the adaptations to various physiological systems in response to training. This study aimed to compare systemic myokines’ (apelin, interleukin-6 [IL-6], interleu-kin-15 [IL-15], fibroblast-growth factor-21 [FGF-21], and irisin) responses to acute moderate-intensity cardiovascular exercise (MICE), high-intensity interval exercise (HIIE), or resistance exercise (RE). Methods: Six healthy, recreationally active adults (n = 4 males, n = 2 females) completed this crossover pilot study. After baseline testing, in a balanced randomized order, participants completed all three exercise sessions with one week between each of the exercise sessions. Blood samples were obtained at rest, immediately post-exercise, and 1 and 3 h post-exercise. Myokine response was analyzed using a 3 (exercise condition: MICE, HIIE, RE) × 4 (time: baseline, post-exercise, 1 and 3 h post-exercise) repeated-measures ANOVA. Results: Our results showed no significant interaction of time × exercise type in any of the analyzed myokines (all p > 0.05). A significant main effect of time was found for FGF-21, where concentrations at baseline (188.96 ± 127.34 pg/mL; p = 0.038) and immediately post-exercise (206.27 ± 135.95 pg/mL; p = 0.006) were higher than 3 h post-exercise (111.08 ± 127.65 pg/mL). No other main effects for time or exercise type were identified (all p > 0.05). Conclusions: The three exercise types, when analyzed together in this study, demonstrated a reduction in FGF-21 3 h post-exercise, suggesting this myokine was removed from the systemic circulation following exercise. The negative results of this study are inconclusive given the lower statistical power observed in this research. These preliminary results indicate the need for a larger trial to evaluate the effects of different types of exercise on the specificity of myokine responses and how acute exercise responses may translate into long-term exercise training adaptations.

Muscles doi: 10.3390/muscles5010002

Authors: Daido Dagne Bruvere Edgars Bernans

Since the introduction of advanced footwear technology (AFT) in 2017, numerous world records from 5 km to the marathon have been broken. Among these innovations, carbon-plated shoes have received particular attention. Previous research indicates improvements of 2–4% in running economy (RE), which translates into an approximate 1–2% improvement in running performance when running in these shoes. The rapid progression of performance has generated significant scientific interest; however, a clear understanding of the mechanisms driving the effectiveness of AFT remains limited. Despite widespread adoption and remarkable results, the mechanisms underlying the effectiveness of AFT are still not fully understood, which is why optimising its potential benefits continues to be an ongoing challenge. This review summarises current knowledge on AFT and critically evaluates the biomechanical and physiological mechanisms underlying their effects on RE and performance. It also highlights the interaction between shoe design features and individual biomechanics, supporting evidence-based approaches to footwear selection and training strategies tailored to athletes’ needs. A clearer understanding of these mechanisms may provide valuable insights for researchers, coaches, and athletes and help maximise the potential benefits of AFT.

Muscles doi: 10.3390/muscles5010001

Authors: Mohammad Rahman Rahimi Hassan Faraji Chenour Sadeghi George John Ildus I. Ahmetov Hadi Golpasandi

Background: Pentraxin 3 (PTX3) is a key biomarker of innate immunity and inflammation, associated with muscle mass, metabolic syndrome, and obesity-related indicators. However, its role in training adaptations remains unclear, with studies reporting inconsistent PTX3 responses to acute and chronic exercise. This study aimed to compare the effects of aerobic exercise, resistance training, high-intensity interval training (HIIT), and acute exercise on PTX3 levels. Methods: A systematic search using Boolean logic was conducted in Web of Science, PubMed, and Google Scholar to identify randomized controlled trials examining the effects of exercise training and acute exercise on PTX3 levels. Results: Out of 3434 records published from 1992 to July 2025, 19 studies met the eligibility criteria. Meta-analysis revealed that aerobic training significantly increased PTX3 levels (SMD = 0.71; 95% CI, 0.173 to 1.252; p = 0.01; I2 = 83.14%), whereas resistance training significantly reduced them (SMD = −0.69; 95% CI, −1.025 to −0.370; p = 0.0001; I2 = 17.52%). HIIT did not elicit a significant change (SMD = 0.086; 95% CI, −0.364 to 0.535; p = 0.70; I2 = 0.00%). Notably, exercise training significantly elevated PTX3 in individuals over 50 years old (SMD = 1.124; 95% CI, 0.231 to 2.017; p = 0.014; I2 = 87.97%) but not in younger participants (SMD = −0.156; 95% CI, −0.640 to 0.327; p = 0.526; I2 = 78.80%). Conclusion: Aerobic and resistance exercise exert opposing effects on PTX3, suggesting distinct mechanisms through which different training modalities modulate inflammatory pathways relevant to muscle metabolism and repair. Acute exercise may also transiently elevate PTX3 to manage exercise-induced inflammation.

Muscles doi: 10.3390/muscles4040062

Authors: Regine Y. S. Zhou Lachlan P. James Danny Lum

Researchers comparing countermovement (CMJ) and assisted countermovement (ACMJ) jumps reported conflicting findings on the landing impact force (LIF). This was likely due to differences in the landing strategies used. As the magnitude of LIF may have implications on neuromuscular adaptations, the purpose of this study was to compare the LIF between CMJ and ACMJ while adopting soft and stiff landing strategies. Thirteen resistance-trained athletes (sex: female = 5, male = 8, 26.4 ± 3.7 years, 68.4 ± 13.6 kg, 167 ± 5.1 cm) performed three CMJ and ACMJ each at 60%, 70%, 80% and 90% of bodyweight with instructions to either land soft or stiff on a force plate. Repetitions were separated by 30 s and conditions by 3 min. Resistance bands were used to induce the required weight during ACMJ. Data obtained regarding the average of the two closest trials based on jump height was analysed. Jump height significantly increased with increasing assistance during ACMJ for both landing conditions (p < 0.001). Propulsion duration (PD) was significantly shorter with increasing assistance during ACMJ for both landing conditions (p < 0.001). Peak and mean propulsion force significantly decreased with increasing assistance during ACMJ for both landing conditions (p < 0.001 and p < 0.001, respectively). The LIF was significantly greater with increasing assistance during ACMJ in the stiff-landing condition only (p < 0.001). Greater assistance allowed participants to jump higher while reducing PD. The higher LIF observed during stiff landing with greater assistance during ACMJ could be attributed to greater jump height and downward velocity during landing.

Muscles doi: 10.3390/muscles4040063

Authors: Sebastián Eustaquio Martín Pérez Eduardo Iboleón Laynez José Antonio Acevedo Rodríguez María Isabel Maggioni Torres Roberto Pérez Betancort Antón Díaz Rodríguez Diego Cabezos Alonso Carlos García Camacho Isidro Miguel Martín Pérez

Background: Musculoskeletal pain syndromes (MPSs) represent a major cause of disability and reduced quality of life, and conventional therapeutic approaches often provide only partial or temporary relief. Hyperbaric oxygen therapy (HBOT) delivered as 100% oxygen at 1.3–2.5 ATA, has been proposed to modulate inflammatory processes and enhance tissue repair. This review evaluated the effectiveness of HBOT on pain, function, quality of life, and physiological outcomes in individuals with MPS. Methods: This systematic review was conducted in different databases between June 30 and 30 September 2025, following PRISMA guidelines and was previously registered in PROSPERO (CRD420251073730). Studies published in English, Spanish, or Portuguese evaluating HBOT as a standalone or adjunctive intervention were included. Methodological quality and risk of bias were assessed using PEDro, NIH, and RoB 2.0 tools, and certainty of evidence was graded with GRADE. Results: Eighteen studies (17 RCTs and 1 case series; n = 671) were included. HBOT protocols ranged from 3 to 60 sessions, lasting 60–90 min, at approximately 1.3–2.5 ATA. Consistent reductions in pain and modest functional improvements were observed in fibromyalgia and postoperative conditions such as knee arthroplasty and peripheral nerve repair, with associated improvements in quality of life and inflammatory markers. Results for delayed-onset muscle soreness and acute ligament injuries were inconsistent. Conclusions: HBOT may provide adjunctive benefits in musculoskeletal pain syndromes, yet the current evidence remains limited. Standardized treatment protocols and high-quality trials are needed to better define its clinical applicability.

Muscles doi: 10.3390/muscles4040061

Authors: Brayden Worley Brennan J. Thompson Jon Carey Talin Louder

Falls are a leading cause of injury and loss of independence in older adults, often linked to deficits in lower-limb muscle function and gait mechanics. Eccentric exercise can improve muscular resilience, while aquatic walking offers a safe, supportive environment to retrain gait; however, little is known about how these modalities interact at the neuromuscular level. This study compared lower-limb muscle activation during gait on land and in water, before and after an acute bout of eccentric exercise, in healthy young adults. Surface electromyography was collected from the tibialis anterior (TA), gastrocnemius medialis (GM), vastus lateralis (VL), and biceps femoris (BF) during treadmill walking on land and at equivalent speeds in chest-deep water. Results showed that aquatic walking consistently altered activation patterns relative to land walking, with increased TA activity (28%, Cohen’s d = 0.69) and reduced GM activity (−27%, Cohen’s d = −0.48) during swing, reduced VL activity during stance (−20%, Cohen’s d = −0.43), increased VL activity during swing (46%, Cohen’s d = 0.72), and increased BF activity during stance (51%, Cohen’s d = 0.63). These changes produced distinct co-activation patterns between the shank and thigh. Eccentric exercise had limited effects overall but increased thigh co-activation during swing in land walking. Findings suggest that eccentric exercise can be safely combined with aquatic walking and highlight the potential of this multimodal approach for enhancing gait mechanics relevant to fall prevention.

Muscles doi: 10.3390/muscles4040060

Authors: Haley M. Nguyen Sophia L. Porrill Rebecca R. Rogers Josselyn Jose-Gomez Rachel E. Wright Phoebe N. Spears Christopher G. Ballmann

Introduction: Red spinach powder (RSP) contains high amounts of inorganic nitrate/nitrite (NO3/NO2), which has been suggested to alter vascular activity, cognitive processing, and sprint exercise performance. There have been few investigations as to whether RSP serves as an ergogenic aid to improve resistance exercise performance, particularly muscular endurance. Purpose: The purpose of this study was to investigate acute RSP (VitaSpinach®) supplementation on muscular endurance and velocity during bench press exercise. Methods: In a double-blind, counterbalanced crossover manner, resistance-trained males (n = 14) were subjected to two supplement conditions as follows: (1) placebo (PL; purple sweet potato) or (2) red spinach powder (RSP; 400 mg NO3). Supplements were consumed 2 h prior to exercise and blood was collected immediately pre-exercise to determine NO3/NO2 levels. To determine barbell velocity, participants completed two sets × two repetitions with maximal effort, while a rotary encoder measured mean barbell velocity. Following this, participants performed three sets × repetitions to exhaustion (RTE) at 60% of 1-Repetition Maximum (1-RM), separated by 2 min of rest, to determine muscular endurance. Local (lRPE) and global (gRPE) ratings of perceived exertion were measured after exercise. Blood NO3/NO2, RTE, mean velocity, lRPE, and gRPE were compared between supplement conditions. Results: RSP resulted in significantly higher blood levels of total NO3/NO2 (p < 0.001) compared to PL. RSP did not result in superior total RTE (p = 0.935) but increased mean velocity (p = 0.035) compared to PL. Both lRPE (p = 0.027) and gRPE (p = 0.028) were significantly reduced with RSP supplementation. Conclusions: Findings suggest acute RSP ingestion increased NO3/NO2 and bench press velocity. While muscular endurance remained unchanged, RSP resulted in lower perceptions of exertion.

Muscles doi: 10.3390/muscles4040059

Authors: Valentina Baldini Giorgia Varallo Andi Nuredini Rossella Tupler Giuseppe Plazzi Diana De Ronchi Maria Carmela Pera Rocco Liguori Sandro Rubichi Maristella Scorza

Neuromuscular diseases (NMDs) include a heterogeneous group of progressive chronic conditions that frequently lead to substantial physical disability and loss of autonomy. Although motor and functional impairments of NMDs are well documented, the psychological burden remains underexplored. This narrative review synthesizes current literature regarding four psychological domains in individuals with NMDs: (i) anxiety, (ii) depression, (iii) coping strategies, and (iv) quality of life. Evidence indicates that anxiety and depressive symptoms are highly prevalent in the spectrum of NMDs, influenced by factors such as disease severity, onset age, and perceived social support. Maladaptive coping strategies, including avoidance and denial, are associated with poorer mental health outcomes and reduced involvement in rehabilitation. In contrast, adaptive strategies, such as acceptance and problem-focused coping, may help buffer psychological distress. Quality of life is consistently reported to be lower in people with NMDs compared to the general population, with psychosocial factors such as social support playing a role. Despite these findings, psychological care remains inconsistently integrated in NMD management.

Muscles doi: 10.3390/muscles4040058

Authors: Andres Parga Dhruv Ratra Dana Luu

Dermatomyositis (DM) is a prototypic idiopathic inflammatory myopathy in which characteristic skin disease frequently precedes or parallels muscle involvement and signals risks such as interstitial lung disease (ILD) and malignancy. This literature review integrates recent advances across dermatology, neuromuscular medicine, and immunology to refine diagnosis and management. We surveyed the literature from 2000 to 2025, prioritizing randomized trials, large cohorts, and translational studies that spanned classic and juvenile DM, amyopathic/hypomyopathic variants, and overlap phenotypes. Key insights include the diagnostic weight of pathognomonic cutaneous lesions with nailfold microangiopathy; the utility of myositis-specific autoantibodies for endotyping and risk (e.g., anti-TIF1-γ/anti-NXP2 and cancer, anti-MDA5 and rapidly progressive ILD); and the value of myxovirus-resistance protein A (MxA) immunohistochemistry and muscle MRI patterning (including distinctions from immune-mediated necrotizing myopathy) when enzymes are normal, or biopsies are treatment-modified. Management is anchored in early steroid-sparing immunosuppression tailored to phenotype, with evidence for IVIG in active DM and growing support for JAK inhibition, particularly in interferon-high or anti-MDA5 ILD, alongside selective use of calcineurin inhibitors and rituximab, with plasma exchange considered for refractory, rapidly progressive ILD. We highlight risk-stratified malignancy screening (IMACS 2023) and complications, including calcinosis, lipodystrophy, and chronic cutaneous damage. Skin-led recognition coupled with antibody-guided, phenotype-directed therapy and interdisciplinary care offers a pragmatic precision framework to improve outcomes and reduce long-term disability.

Muscles doi: 10.3390/muscles4040057

Authors: Sérgio Zabotto Dantas Danielli Candido Munhoz Evangelista Bruna Zampieri Nogueira Cozza Marcelo Dib Bechara Sandra Maria Barbalho Eduardo Federighi Baisi Chagas Adriano Cressoni Araújo Elen Landgraf Guiguer Camila Maria de Arruda Juliana da Silva Soares de Souza Karina Quesada Cláudia Rucco Penteado Detregiachi

Background/Objectives: Despite the increasing use of ultrasound (US) as a tool for assessing muscle mass and diagnosing sarcopenia, its application remains limited because few studies have validated cut-off points for specific populations. This study aimed to propose US cut-off points for diagnosing sarcopenia in Brazilian individuals aged 60 years and older. Methods: Patients schedule for elective abdominal computed tomography (CT) were also evaluated with musculoskeletal US of the thigh. CT images were obtained at the level of the third lumbar vertebra. US measurements included the thickness of the rectus femoris (RF) muscle and the rectus femoris combined with the vastus intermedius (RF + VI). Receiver Operating Characteristic (ROC) curves determine the sensitivity and specificity of the US cut-off points. The area under the curve (AUC) and 95% confidence intervals (CI) were calculated. Results: The study sample (n = 88) had a mean age of 71.8 ± 8.7 years, and 64% were women. The proposed cut-off points for diagnosing sarcopenia using US, based on the mean ± SD, were ≤19.1 mm and ≤15.9 mm for RF thickness and ≤31.9 mm and ≤29.2 mm for RF + VI thickness in men and women, respectively. These cut-off points demonstrated good accuracy and significant AUC values. Conclusions: This study proposes US-based cut-off points with good accuracy for suggesting sarcopenia diagnosis, particularly when assessing RF thickness.

Muscles doi: 10.3390/muscles4040056

Authors: Mark E. T. Willems Sam D. Blacker Ian C. Perkins

Intake of anthocyanin-rich blackcurrant extract showed muscle fibre-type specific force responses during fatigue development from combined use of voluntary maximal isometric contractions and electrically evoked twitch contractions of the m. quadriceps femoris. In the present exploratory study, we examined the fibre-type specific effects by blackcurrant extract on high-intensity intermittent treadmill running performance to exhaustion. Active males (n = 16, age: 23 ± 3 years, height: 179 ± 5 cm, body mass: 79 ± 3 kg, V˙O2max: 55.3 ± 5.0 mL·kg−1·min−1) completed a fatiguing protocol with 16 voluntary maximal isometric contractions to predict muscle fibre typology. The high-intensity intermittent running protocol was completed twice following a 7-day intake of blackcurrant extract (210 mg anthocyanins per day) and twice following a placebo (PL) in a randomized, double blind, crossover design. Heart rate and lactate were recorded at exhaustion. Data were averaged for each condition. There were no significant correlations between the percentage force decline by the repeated isometric contractions (mean ± SD: 29.3 ± 12.4%) and total and high-intensity running distance. Participants were categorized into a predominant muscle fibre type I (slow-twitch, n = 3 with the lowest isometric force decline: 12 ± 9%) and type II typology (fast-twitch, n = 3 with the highest isometric force decline: 46 ± 10%). Only the individuals with a predominant type I fibre typology improved the total running and high-intensity running distance by 17 ± 12% and 15 ± 11%. At exhaustion, there were no differences between individuals with a type I or II fibre typology for heart rate and lactate. These exploratory results suggest that the ergogenic potential of anthocyanin-rich blackcurrant extract on high-intensity intermittent exercise may depend on muscle fibre type, though larger and more robust studies are needed to confirm this observation. Future work will establish whether our exploratory results contributed to our understanding of the underpinning of inter-individual responses to the intake of anthocyanin-rich nutritional ergogenic aids.

Muscles doi: 10.3390/muscles4040055

Authors: Hyeon Yu

Sarcopenia, the loss of skeletal muscle mass and function, is a common and critical comorbidity in patients with conditions frequently managed by interventional radiologists, such as liver cirrhosis and hepatocellular carcinoma (HCC). Interventional radiologists are well positioned to incorporate opportunistic screening for this condition during routine preprocedural cross-sectional imaging. This review summarizes the current evidence on how sarcopenia influences patient outcomes and informs procedural planning across a spectrum of interventional radiology (IR) procedures. In transarterial embolizations for HCC, sarcopenia is a robust independent predictor of increased mortality, with meta-analyses suggesting it may also predict a lower tumor response rate. Even earlier stages of muscle loss (pre-sarcopenia) are associated with worse survival, and dynamic changes in muscle mass post-treatment can serve as a biomarker for tumor progression. For patients undergoing transjugular intrahepatic portosystemic shunt, pre-procedural sarcopenia and myosteatosis are strong, independent predictors of both mortality and the development of post-procedural hepatic encephalopathy, with the presence of both conferring the highest risk. In the context of pre-surgical portal vein embolization, sarcopenia is consistently associated with impaired volumetric liver growth, although this does not always translate to worse short-term surgical outcomes, as functional liver regeneration may be preserved. Following percutaneous liver tumor ablation, sarcopenia is a powerful predictor of overall mortality, while its role in predicting tumor recurrence remains an area of active investigation. Finally, in non-oncologic interventions for peripheral arterial disease, sarcopenia is highly prevalent and is associated with worse functional status, higher mortality, and a significantly increased risk of major amputation after endovascular therapy. In conclusion, sarcopenia is a powerful and readily available biomarker that provides crucial prognostic information—often independent of standard clinical scores—across a wide spectrum of IR procedures. The consistent evidence supports integrating sarcopenia evaluation into routine practice to enhance risk stratification, improve patient counseling, and guide multidisciplinary treatment planning.

Muscles doi: 10.3390/muscles4040054

Authors: Andrew Usher John Babraj Adam Younger

Football requires repeated sprint ability for game-changing moments; however, the demand on the skeletal muscles is unknown. The aim of the current study was to determine the muscle oxygen response during duplicate sprints in professional footballers. Eight male professional footballers (age: 29 ± 5 y; height: 181 ± 8 cm; weight: 78 ± 8 kg) were recruited. Participants wore their normal GPS unit and completed their normal match warm-up before near-infrared monitors were attached to the rectus femoris and bicep femoris muscles. Participants then completed two 30 m sprints with 10 s of recovery, while GPS data and muscle oxygenation were recorded. Max speed was unaltered across the two sprints (s1: 8.4 ± 0.3 m.s−1; s2: 8.4 ± 0.4 m.s−1), but max acceleration (s1: 5.0 ± 1.5 m.s−2; s2: 3.7 ± 1.2 m.s−2) and time to max acceleration (s1: 1.0 ± 0.3 s; s2: 1.8 ± 0.8 s) were significantly different in sprint 2 compared with sprint 1. Change in muscle oxygenation was greater in the bicep femoris muscle than in the rectus femoris muscle in sprint 1 (right BF: 37.0 ± 14.7%; right RF: 23.4 ± 14.8%). Time to fast delay was longer in sprint 2 than in sprint 1 in the bicep femoris muscle (right BFs1: 1.6 ± 1.2 s; right BFs2: 5.2 ± 2.3 s), reflecting different recovery kinetics in the two muscles. During duplicate sprints there is a difference in oxygen response between the two muscles, and the overall recovery of the bicep femoris is much slower. This suggests poorer conditioning of the bicep femoris muscle, which may impact injury risk in professional football players.

Muscles doi: 10.3390/muscles4040053

Authors: Nataliya Slater Abha Chopra Ramesh Ram Abbie Adams Frank L. Mastaglia Merrilee Needham Jerome D. Coudert

Inclusion body myositis (IBM) is a late-onset, treatment-resistant inflammatory myopathy. Approximately half of IBM patients develop autoantibodies against cytosolic 5′-nucleotidase 1A (cN1A), but their role in disease pathogenesis remains unclear. This pilot study examined the effects of anti-cN1A-positive IBM serum on human primary myotubes’ transcriptome profile, using anti-cN1A-negative IBM and healthy sera as controls. Exposure to anti-cN1A-positive serum altered the expression of 1126 genes, with upregulation of adaptive immune response genes, notably CTSH and CTSZ, encoding cathepsins H and Z. These findings were validated using a publicly available independent dataset comprising transcriptomes from fresh muscle tissue samples. NT5C1A mRNA, which encodes cN1A, was not detected in cultured myotubes regardless of the presence of autoantibodies. The findings suggest distinct pathological mechanisms in anti-cN1A-positive IBM, independent of direct antibody-target interactions. The role of cathepsins in IBM pathogenesis warrants further investigation.

Muscles doi: 10.3390/muscles4040052

Authors: Zakaria Rostamitehrani Rida Javed Linda Popplewell

Duchenne muscular dystrophy (DMD), which results from mutations that disrupt the expression of dystrophin proteins, is characterized by progressive muscle fiber wasting and the development of skeletal muscle fibrosis. The severe pathology leads to loss of ambulation, respiratory insufficiency, cardiomyopathy, and early death in patients. Dystrophin-focused therapies based on adeno-associated viral (AAV) vector-mediated gene addition, antisense oligonucleotide-induced repair of the transcript reading frame, and chemically driven stop codon readthrough have been conditionally approved for use in subsets of patients. From trials, it is apparent that these therapies act to stabilize the disease phenotype rather than improve it significantly, meaning that early treatment results in better outcomes. AAV-mediated delivery of a form of utrophin, a structural and functional homolog of dystrophin, GALGT2, a sarcolemmal stabilizer, and Klotho, the anti-aging hormone that is silenced in a mouse model of DMD as a result of the disease pathology, have been explored in preclinical compensatory gene addition studies. Recombinant follistatin protein has been used to target the fibrosis seen. An all-in-one type of therapy is likely to provide a synergistic effect such that efficacy of the dystrophin restoration strategy would be improved. For this, CRISPRa could hold potential through the targeting of multiple relevant genes simultaneously. The suitability of targeting these genes will be discussed, as will the stages of the development of CRISPRa for DMD. A perspective on the future prospects of CRISPRa in relation to likely issues that would need addressing and how they may be overcame will be given.

Muscles doi: 10.3390/muscles4040051

Authors: Yuliia Moskalenko Viktor Kovchun Ihor Vynnychenko Roman Moskalenko

Sarcopenia and reduced skeletal muscle radiodensity have been proposed as potential biomarkers influencing the outcomes of immunotherapy in cancer patients. This retrospective study aimed to evaluate the prognostic significance of skeletal muscle index (SMI) and skeletal muscle radiodensity (SMD), assessed by means of computed tomography imaging at the L3 level, in 76 male patients with metastatic non-small cell lung cancer treated with PD-1/PD-L1 inhibitors. Patients were categorized into high and low SMI/SMD groups based on body mass index-adjusted cut-off values. Clinical outcomes included treatment response, overall survival, and immune-related adverse events. While no statistically significant differences in overall survival were observed between groups stratified by SMI or SMD, patients with higher SMD demonstrated a significantly greater disease control rate (56.22 ± 8.04 vs. 48.36 ± 10.34 HU; p = 0.031). Additionally, a statistically significant interaction was observed between PD-L1 expression and SMI (p = 0.027), indicating that muscle mass may influence the prognostic value of PD-L1. Neither SMI nor SMD were associated with immune-related adverse event incidence. Multivariate analysis identified PD-L1 expression ≥ 50% as the only independent predictor of longer overall survival (Hazard Ratio = 0.29; p = 0.001). In conclusion, while neither SMI nor SMD independently predicted overall survival, SMD was associated with treatment response. Notably, SMI modified the prognostic relevance of PD-L1 expression, suggesting a potential role for muscle mass in refining immunotherapy stratification.

Muscles doi: 10.3390/muscles4040050

Authors: Afxentios Kekelekis Rabiu Muazu Musa Pantelis T. Nikolaidis Filipe Manuel Clemente Eleftherios Kellis

Hamstring strain injuries (HSI) are common in soccer and remain challenging to predict, as traditional risk factors often fail to capture the multifactorial nature of injury susceptibility. This prospective cohort study aimed to develop and internally validate a machine learning-assisted logistic regression model for predicting hamstring injuries in amateur soccer players using preseason clinical and strength-related variables. A total of 120 male players were followed for one competitive season (30 weeks). Baseline predictors included age, body mass index, previous injury, and bilateral isometric hip and knee strength measured via handheld dynamometry. Twenty initial predictors were reduced to ten through symmetrical uncertainty feature ranking before training a logistic regression model with elastic-net regularization (training set: n = 83; test set: n = 37) using nested four-fold cross-validation. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC), calibration metrics, and confusion matrices. During follow-up, 21 players sustained at least one HSI (32 events; 28% reinjuries), yielding an events-per-variable ratio of 2.1, below ideal thresholds and suggesting possible overfitting. On the independent test set, the model achieved an accuracy of 64.9%, AUC of 0.68 (95% CI 0.52–0.84), calibration slope of 0.85, and intercept of −0.12, with a sensitivity of 60% and specificity of 65.6%. Dominant-leg hip abduction strength was the only statistically significant predictor (OR = 0.82, 95% CI 0.70–0.96), while permutation importance analyses identified previous hamstring injury as the most stable contributor to model performance. Neither age nor hamstring isometric strength demonstrated predictive value. Although model discrimination was moderate and calibration indicated mild overfitting, findings reinforce the prognostic relevance of prior injury and suggest that reduced hip abduction strength may serve as an emerging candidate marker. This study, classified as a TRIPOD Category 2 model (development without external validation), provides preliminary, hypothesis-generating evidence supporting the use of multivariate strength and history-based predictors in future, larger-scale injury prediction research.

Muscles doi: 10.3390/muscles4040049

Authors: Luís Correia Paulo Carvalho Luísa Amaral Mário Esteves Rui Vilarinho Mariana Cervaens

Chronic whiplash-associated disorders describe a cluster of symptoms that result from a sudden neck acceleration/deceleration movement, including pain, musculoskeletal and neurological signs, inducing functional disability. The aim of this study was to compare the effects of physiotherapy treatment based on neck-specific exercises, with or without a behavioral approach, in individuals with whiplash-associated disorders. Computerized research was performed in PubMed, PEDro, National Institute for Health and Care Excellence, and ScienceDirect to identify randomized controlled trials that evaluated the effectiveness of neck-specific exercises, with or without a behavioral approach, for chronic whiplash. For the meta-analysis, the outcomes of pain and disability were assessed. Thirteen studies were included in the systematic review, with a total of 2427 participants of both sexes, with ages between 18 and 63 years. Although interventions with a behavioral approach decreased pain and disability more significantly in 4 and 6 studies when compared to neck-specific exercises without such an approach, respectively, the meta-analysis revealed no differences between them. Although interventions for chronic whiplash-associated disorders based on neck-specific exercises with a behavioral approach seem to be more effective in reducing pain and disability, there is no quantitative difference favoring one over the other.

Muscles doi: 10.3390/muscles4040048

Authors: Nashwa Cheema Namrata Ghag Linh Pham Emma Wise Christiane Fuchs Rox Anderson Joshua Tam

Light therapy has been shown to produce several beneficial physiological effects in a wide range of tissues. The musculoskeletal system can be irradiated with deeply penetrating wavelengths in near infrared (NIR) regions. Photobiomodulation therapy (PBMT) reduces pain and inflammation and enhances physical performance. However, the mechanism(s) of cellular responses to PBMT in muscle is not clearly understood. Therefore, the goal of this study is to improve our understanding of the mechanism(s) of action of PBMT effects in exercised and sedentary muscle. In sedentary mice, PBMT using a wavelength of 830 nm increased the gene expression for muscle tissue development, including cFos, which is critical for activating interstitial and satellite cells that repair muscle. Immunostaining for cFOS expression confirmed an increase in the number of activated cells in PBMT-treated muscle. We observed that PBMT-treated mice showed increased performance on the treadmill, reduced muscle fiber damage, and altered mitochondrial structure. RNA sequencing from fatigued TA tissue suggested that PBMT treatment increased the gene expression of tissue regeneration and remodeling, suggesting tissue adaptation and muscle repair after exercise with PBMT. In conclusion, our study suggests that the 830 nm wavelength may have altered the muscle by activating regenerative genes that protect the tissue from exercise-induced cellular stress.

Muscles doi: 10.3390/muscles4040047

Authors: Katherin S. Huang Filzah Diana Binte Roslan Hong Hin Cheong Jeremy J. Woo Kian Wee Tan Kim Swee Shu-Ying Liang Wei Xi Lau Meredith T. Yeung

Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are commonly used proxies to measure respiratory muscle strength. Current literature lacks recent large-scale normative reference values (NRV) for these pressures in healthy Singaporean adults. Moreover, no consensus exists on the variables that could influence MIP and MEP. This cross-sectional study aims to: (1) establish the NRV of MIP and MEP; (2) determine the correlations of variables that could influence these pressures; and (3) develop regression equations using non-spirometry variables to estimate reference values for MIP and MEP in the healthy Singaporean population aged 21 to 80 years. MIP and MEP were measured alongside demographic and anthropometric data collected from 391 participants (202 females, 189 males) recruited via convenience sampling. Median MIP and MEP values were significantly higher in males (112 and 85 cmH2O) than in females (83 and 64 cmH2O). Spearman correlations revealed significant associations between MIP/MEP and gender, height, weight, body mass index (BMI), waist–hip ratio, and spirometric variables. Regression models using age, gender, height, and weight explained 27.5% and 32.1% of the variance in MIP and MEP, respectively. This study updated the NRV of MIP and MEP and provided practical predictive equations for assessing respiratory muscle strength in Singapore.

Muscles doi: 10.3390/muscles4040046

Authors: Guglielmo Duranti

MDPI’s Muscles is celebrating a highly positive 2025 [...]

Muscles doi: 10.3390/muscles4040045

Authors: Koulla Parpa Antreas Vasiliou Marcos Michaelides Karuppasamy Govindasamy Anton Chernov Konstantina Intziegianni

Although previous studies have examined various factors that influence biceps brachii activation, such as grip position, load, and exercise variation, to our knowledge, no prior studies have compared muscle activation during a traditional biceps curl and a Bayesian cable curl. Therefore, this study aimed to examine the differences in biceps brachii muscle activation between these two training modalities. Data from eleven volunteers (age: 25 ± 6 y; weight: 86 ± 13 kg; height: 177 ± 8 cm) were included in the analysis. Muscle activity was assessed using the normalized root mean square (RMS) values obtained from surface electromyography (sEMG). A within-subjects, counterbalanced design was utilized where all participants completed both testing conditions in a randomized order to control for potential order effects. Participants visited the laboratory and fitness center on two occasions. On the first day, anthropometric measurements were obtained, along with one repetition maximum (1-RM) for both the dumbbell biceps curl and the Bayesian curl. On the second day, participants performed an isometric maximal voluntary contraction (MVC), followed by electromyographic assessment of muscle activity during the dumbbell biceps curl and the Bayesian curl, each performed at 80% of their respective 1-RM. When the normal distribution was confirmed via the Shapiro–Wilk test (p > 0.05), a paired t-test was used for statistical analysis. On the other hand, when normality was not confirmed, the Wilcoxon test was utilized. Statistically significant differences (p = 0.003) were observed in the EMG amplitude (%) between the biceps curl (111.46 ± 26.80) and the Bayesian curl (93.39 ± 15.65) with a large effect size (d = 0.82). Based on the EMG analysis, the dumbbell biceps curl elicited significantly greater muscle activation compared to the Bayesian curl, suggesting that the conventional movement places a higher mechanical and neuromuscular demand on the biceps brachii.

Muscles doi: 10.3390/muscles4040044

Authors: Nicholas Ripley Christopher Bramah Paul Comfort John McMahon

Applied muscular strain and hamstring strain capacity have a joint interaction on hamstring strain injury (HSI) with modifiable risk factors frequently assessed. However, to date there is limited observations on the interaction between these factors. The purpose of the present study was to observe if spatiotemporal characteristics, running kinematics and muscle activation were related to modifiable risk factors of HSI. Twenty-two competitive team sport athletes (24.7 ± 4.3 years, 1.82 ± 0.07 m, 84.9 ± 8.5 kg) participated whereby the Bicep femoris long head (BFLH) fascicle length assessed via ultrasound and isokinetic eccentric hamstring strength was assessed. With running assessment performed at 18 km/h, capturing running kinematics and muscle activation. Multiple linear regressions were used to examine the relationship of running kinematics and muscle activation on the modifiable risk factors of HSI on. The overall model (F2,19) was statistically significant for both relative eccentric hamstring strength (F = 23.58, p < 0.001) and BFLH fascicle length (F = 18.87, p < 0.001) highlighting spatiotemporal characteristics, running kinematics and hamstring activation were found to be significantly related to the modifiable risk factors. There is a complex interrelationship between running mechanics and hamstring muscle properties, with the potential of either cause or consequence association.

Muscles doi: 10.3390/muscles4040043

Authors: Jaume Barrera Imanol Amayra David Contreras Alicia Aurora Rodríguez Nicole Passi Javiera Ortega Óscar Martínez

Aim: The study developed and validated AppER, an mHealth tool for informal caregivers of children with Duchenne Muscular Dystrophy, and examined differences between app users and non-users. Methods: Four phases were followed: (1) focus groups with experts and caregivers to identify care-related domains; (2) prototype development and validity testing (CVR, I-CVI, I-FVI) using the MARS scale; (3) implementation of the final app; and (4) psychosocial profiling of 88 caregivers (42 users and 46 non-users) measuring quality of life, dependency, somatic symptoms, and coping strategies. Results: AppER showed high content and face validity, surpassing reference thresholds. In the psychosocial analysis, users reported lower perceived quality of life than non-users, despite no significant differences in dependency, somatic symptoms, or coping strategies. Conclusions: Employment patterns differed: more users were dedicated to household tasks, while more non-users were self-employed, suggesting economic factors may affect app uptake and quality of life perceptions. Findings indicate AppER is a valid, well-rated support tool, and that caregivers with lower perceived quality of life may be more inclined to adopt digital health solutions, potentially to address complex care demands. Designing targeted digital interventions may be particularly valuable for those in less favorable socioeconomic contexts. Because of the small sample and between-group imbalances, results are exploratory and warrant confirmation in larger, balanced samples.

Muscles doi: 10.3390/muscles4040042

Authors: Alessandro Cudicio Marta Cogliati Gianluca Rizzi

Purpose: Despite significant attention being paid to compression garments (CG) in the sports field, there remains ongoing debate regarding their actual effectiveness in enhancing athletic performance and expediting post-exercise recovery. This article examines their various aspects, with a focus on CG design and the materials they are made of, aiming to analyze the importance of personalized compression strategies based on individual anthropometric measurements and non-linear compression designs. Methods: Using anthropometric analysis of 40 healthy participants, this study examines the morphological characteristics of the lower limb and their implications for CG design. Results: Measurements of limb length and circumferences revealed complex interactions among anatomical variables, emphasizing the need for customized and adaptable device design. Finite element simulations clarified the challenges in achieving uniform pressure gradients along the lower limb, highlighting the limitations of one-piece devices and suggesting tailored segmented designs for individual limb segments. Conclusion: The results demonstrate that one-piece devices often fail to provide optimal compression due to non-linear variations in limb dimensions. Conversely, segmented devices, particularly those with bilinear progression, exhibited superior performance in applying targeted compression across different limb segments. This more detailed approach to customization could significantly contribute to optimizing outcomes and user comfort.

Muscles doi: 10.3390/muscles4030041

Authors: Steven Hopkins Paulomi Gohel Sakshi Gandhi Moiz Nasir William Stallings Eman Hamad

Background: Sarcopenia is associated with adverse surgical outcomes across multiple specialties. The psoas muscle index (PMI), a radiologic marker of sarcopenia, may offer prognostic value in patients undergoing left ventricular assist device (LVAD) implantation, a population frequently characterized by frailty and high perioperative risk. Methods: We conducted a single-center retrospective study of 32 patients who underwent LVAD implantation between 2017 and 2022 and had preoperative CT imaging within 45 days. PMI was calculated from bilateral psoas muscle area at the L3 vertebral level, normalized to height. Sarcopenia was defined as the lowest sex-specific quartile of PMI. Primary outcomes were overall survival (OS), 90-day mortality, and postoperative length of stay (LOS). Results: Eight patients (25%) met criteria for sarcopenia. Sarcopenic and non-sarcopenic groups had similar demographics, comorbidities, and nutritional status. While there were no significant differences in overall, 90-day, or 1-year mortality between groups, among those who died post-implantation, the sarcopenic group had significantly shorter OS (median 38 vs. 597 days, p = 0.006). All sarcopenic deaths occurred within 90 days post-implant. LOS did not differ significantly between groups. Conclusions: PMI-defined sarcopenia was associated with early postoperative mortality among LVAD recipients, though not with overall or long-term mortality.

Muscles doi: 10.3390/muscles4030040

Authors: Manuel B. Almeida Marion Moreira Paula Moleirinho-Alves Raúl Oliveira

This study aimed to investigate if there are differences in neck strength between dental students in their fourth and fifth years, with and without neck pain. Neck muscle strength was assessed in flexion, extension, and lateral flexion to both sides using a handheld dynamometer while participants performed maximum voluntary isometric contractions with a make test procedure. Differences between groups were evaluated through a one-way analysis of variance followed by Tukey’s post hoc comparison. Forty-three students (twenty-one fourth-year and twenty-two fifth-year students) participated in the study. Fifth-year students with neck pain (P5) (n = 14) showed less strength (p = 0.018) compared to the no-pain group (NP) (n = 15) in neck flexion and lateral flexion for both sides (p < 0.001). The fourth-year symptomatic students (P4) (n = 14) showed reduced right lateral flexion strength compared to the NP group (p = 0.035). No significant differences were observed in neck extension across all groups (p = 0.085). Our research indicates a progressive decline in neck muscle strength in flexion and lateral flexion among students with neck pain over their training years. Our findings suggest that this may be linked to the increasing mechanical demands of clinical practice during training, potentially affecting muscle balance and cervical function. This pain could be associated with changes in motor behavior and reduced cervical muscle strength.

Muscles doi: 10.3390/muscles4030039

Authors: Daniel Berlanga de Mingo Guillem Paz Ramírez Arnau Moreno Garcia Maria Tibau Alberdi Diana Noriego Muñoz Miguel Pérez Abad Giacomo Rossettini Jorge Hugo Villafañe César Abellán Miralles Montserrat del Valle Jou Àngel Ferreres Claramunt Alfonso Rodríguez Baeza

Background: The annular ligament is a key secondary stabilizer of the elbow, but its biomechanical behavior during forearm rotation has not been objectively quantified. This study aimed to assess interindividual variability in annular ligament tension, validate prior arthroscopic observations, and explore associations with chondral lesions in the lateral elbow compartment. Methods: In this cross-sectional anatomical study, 25 cadaveric upper limbs were analyzed following standardized dissection, preserving ligamentous and muscular integrity. Ligament displacement was measured using a custom mechanical apparatus and high-precision digital micrometer in neutral, 60° pronation, and 60° supination positions under axial tractions of 1, 2, and 3 kg. Ulnar length and presence of chondral lesions were also recorded. Results: Maximal ligament displacement occurred in supination in 80% of specimens (mean: 1.23 mm at 3 kg; range: 0.30–2.87 mm), indicating considerable interindividual variation. Significant displacement differences were observed between all forearm positions across load levels (p < 0.001). Chondral lesions were identified in three specimens with marked ligament laxity and reduced radial head coverage. Conclusions: This study provides the first objective evidence of annular ligament tension variability during forearm rotation. Ligament laxity may contribute to lateral elbow instability and cartilage degeneration, supporting the ligament’s role as a secondary stabilizer.

Muscles doi: 10.3390/muscles4030038

Authors: Cassandra Evans Jaime Tartar Jonathan Banks Jennifer Austin Jose Antonio

Dietary behaviors influence nutrient intake and body composition, both of which are important determinants of an individual’s overall health. This study investigated sex differences in the associations between dietary behaviors and body composition. Using a cross-sectional design, adults completed the three-factor eating questionnaire (TFEQ-R18) and food cravings (FCI) to assess dietary behaviors. Body composition was assessed using bioelectrical impedance analysis. Relative to males, there were significantly higher levels of cognitive restraint and emotional eating in females. Males exhibited greater cravings for fatty foods and a higher frequency of acting on those cravings. Body fat percentage was positively correlated with emotional eating and cognitive restraint in both sexes. These results suggest that gender and body fat are key factors related to dietary behaviors.

Muscles doi: 10.3390/muscles4030037

Authors: Shelby L. Houchlei Sarah N. Wood Sarah E. Peters Shane K. Miller Taylor K. Dinyer-McNeely Ryan A. Gordon

Potential variability in neuromuscular function or physiology throughout the menstrual cycle (MC) or a cycle of using hormonal contraceptives may affect muscular performance variables that are relevant to exercise, training, or sport. Collegiate softball players (n = 11) that reported using and not using hormonal contraceptives completed three testing sessions during their respective early follicular, ovulatory, and mid luteal phases of the MC or early, mid, or late phases of their hormonal contraceptive cycle (HCC). Each testing session included a series of performance tests: countermovement jump on a force plate, 15-yard sprints, velocity assessment of the back squat performed at 70% of one-repetition maximum (1-RM), one-repetition maximum bench press, and 70% 1-RM repetitions to failure testing on the bench press. No significant differences were found for any of the performance tests between the three phases, though performance on most tasks peaked during the mid luteal/late phases of the MC/HCC. It is important to note that this study was underpowered and this could have masked any observed differences. Collectively, muscular performance was not significantly different throughout phases of the MC or HCC in these athletes, indicating that potential hormonal variability throughout the MC or HCC did not seem to have an effect on performance outcomes in this study.

Muscles doi: 10.3390/muscles4030036

Authors: Ricardo Pimenta Abel Pimenta

Isometric strength is widely used to monitor training adaptations, assess neuromuscular fatigue, and play a critical role in the maintenance of muscle health. This study assessed repeatability (intra-session) and reliability (inter-session) of a force production machine in different exercises: Isometric Mid-Thigh Pull (IMTP), Knee Flexion (KF) at 30°, and Seated Calf Raise (SCR). Parameters measured included Peak Force (PF), RFD at 0–50, 0–100, 0–150, 0–200, 50–100, 100–150 and 150–200 ms. Thirty male individuals (IMTP = 30; KF = 11 and SCR = 30) participated (age: 20.6 ± 3.6 years, mass: 75.3 ± 7.5 kg, height: 1.80 ± 0.64 m). Repeatability and reliability were calculated for bilateral PF and RFD for IMTP and SCR, and unilateral for KF. PF demonstrated good to excellent repeatability in all exercises: IMTP (ICC = 0.93), KF (left: ICC = 0.98; right: ICC = 0.97), SCR (ICC = 0.84). RFD displayed poor to good repeatability in IMTP (ICC = 0.45–0.87) and SCR (ICC = 0.40–0.85), moderate to excellent repeatability in KF (left: ICC = 0.53–0.96; right: ICC = 0.61–0.92). PF reliability was excellent in IMTP (ICC = 0.93) and KF (left: ICC = 0.99; right: ICC = 0.97), and moderate in SCR (ICC = 0.64). RFD reliability was moderate to excellent in IMTP (ICC = 0.58–0.94), poor to good in SCR (ICC = 0.13–0.64), and poor to excellent in KF (left: ICC = 0.33–0.96; right: ICC = −0.19–0.95). This study shows that portable dynamometry can measure maximal and explosive strength in different exercises, demonstrating good reliability for most parameters in IMTP and KF.

Muscles doi: 10.3390/muscles4030035

Authors: Hla Myat Mo Mo Jong Han Lee

Baicalin is a natural flavonoid that has anti-apoptotic and anti-inflammatory effects. It shows some beneficial effects on muscle atrophy. However, its effects on age-related muscle atrophy are poorly understood. In this paper, we investigated whether baicalin exerts protective effect against skeletal muscle atrophy and its underlying mechanisms in aged mice using the grip strength test, histological analysis, and Western blots. Baicalin increased total muscle mass and strength in aged mice. Consistently, the cross-sectional area of quadriceps (QD) muscle significantly increased in both baicalin-administrated groups. Moreover, baicalin induced a shift in muscle fiber size distribution toward large fibers in both groups of mice. Expression levels of muscle atrophic factors, such as myostatin (MSTN) and atrogin-1, as well as pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), were elevated in aged mice, but these increases were reduced by baicalin. While mitochondrial fission regulator, dynamin-related protein 1 (DRP-1), and apoptosis-related protein (apoptotic protease activating factor 1 (Apaf-1)) expressions were higher in aged mice than young mice, and their expression were downregulated following baicalin administration. The comprehensive results of this study suggest that baicalin provides beneficial effects on the treatment of sarcopenia not only by suppressing muscle atrophic factor expression and inflammation but also attenuating DRP-1-mediated mitochondrial fission and apoptosis.

Muscles doi: 10.3390/muscles4030034

Authors: Lucas Ghionna Léa Ruppel Nuno Nogueira Gabriela Brochado Alice Carvalhais

Background: Blood Flow Restriction (BFR) training may be an alternative when traditional heavy-load training is unsuitable. This study compared BFR with light loads to traditional strength training for shoulder muscle development proximal to the occlusion site; Methods: A total of 22 healthy adults were randomized into Group A: BFR training (30% 1RM; n = 12) and Group B: Traditional strength training (70% 1RM; n = 10). Four-week protocol (2 sessions/week) included shoulder abduction and lateral rotation, and dumbbell overhead press. Arm circumference, Single Arm Seated Shot-Put Test (SAASPT), vertical lift strength (VLS) and Shoulder Endurance Test were assessed at baseline and at the end of the protocol. Cohen’s d effect size was calculated for significant outcomes; Results: Significant gains occurred in both groups across most parameters. The magnitude of effects was, in Group A, large on Arm circumference and SASSPT (Cohen’s d = 0.870 and 1.158, respectively) and very large in VLS and SET (Cohen’s d = 1.284 and 1.301, respectively). In Group B, the magnitude of effects was large in SASSPT and VLS (Cohen’s d = 0.962 and 0.922, respectively) and very large in SET (Cohen’s d = 1.238); Conclusion: BFR training with light loads effectively improved musculature proximal to the occlusion site, demonstrating comparable strength gains to heavy-load training in healthy individuals.

Muscles doi: 10.3390/muscles4030033

Authors: Joseph Bryant Darren J. Cooper Derek M. Peters Matthew D. Cook

Static stretching (SS) is commonly used in athletic programs, and the intensity of SS has recently been examined for its effects on range of motion (ROM), strength and passive stiffness. However, the reliability of high-intensity SS across multiple testing sessions has not been investigated. The purpose of this investigation was to examine the reliability of high-intensity SS of the hamstrings across five laboratory visits on ROM, strength, power and passive stiffness. Thirteen physically active males (age: 26 ± 4 years, height: 180 ± 8 cm, body mass: 81 ± 10 Kg) underwent five repeated measures of laboratory SS on an isokinetic dynamometer where point of discomfort (POD) was measured, followed by a 30 s stretch at 120% POD. Across the visits, the pooled intraclass correlation coefficient was good for knee extension ROM (0.82), knee flexion strength (0.81) and passive stiffness (0.81). The ROM achieved to determine the POD before the SS was not different for the five visits (p = 0.370). These findings suggest high-intensity SS to 120% POD on an isokinetic dynamometer is reliable across multiple testing sessions. It is not clear if high-intensity static stretching is also reliable within applied scenarios and warrants further investigation.

Muscles doi: 10.3390/muscles4030032

Authors: Yi Shin Lee Amelia Dingley Danny Lum Frankie Tan John F. T. Fernandes

The main research question of this review involved the identification of the various physiological and physical determinants of flat-water kayaking. A systematic search was conducted using three databases (PubMed, Google Scholar, and Microsoft Academic) between 1991 and December 2022. Quality assessment was performed using a version of the National Heart, Lung and Blood Institute checklist tailored for cross-sectional and observational studies. A total of 169 articles were identified in the initial screening. After duplicate removal and further screening for relevance, a total of 17 articles were included in the review. Altogether, it was found that flat-water kayaking performance was strongly correlated with maximum oxygen uptake (VO2max), aerobic and anaerobic thresholds, peak aerobic and anaerobic capacity measure in lab and on the water, and upper and lower-body strength and power, which were measured using heavy resistance, as well as isometric and isokinetic implements. What is less clear is the association between total lean mass and flat-water kayaking performance. However, this may largely be due to the differences in when the measurements were taken.

Muscles doi: 10.3390/muscles4030031

Authors: Grazia Marinelli Alessio Danilo Inchingolo Irma Trilli Carmela Pezzolla Roberta Sardano Francesco Inchingolo Andrea Palermo Cinzia Maria Norma Maspero Gianna Dipalma Angelo Michele Inchingolo

Background: In recent years, botulinum toxin (BoNT) has been increasingly employed not only as a corrective aesthetic intervention but also as a proactive strategy to delay the visible signs of facial aging. This systematic review aims to evaluate the scientific evidence supporting the preventive role of BoNT in facial aging, focusing on its long-term effects, mechanisms of action, and clinical outcomes when used in younger, pre-symptomatic populations. Methods: A systematic literature search was conducted across PubMed, Scopus, and Web of Science databases. Inclusion criteria encompassed clinical trials and observational studies addressing the use of BoNT for proactive aesthetic strategies. Results: Evidence suggests that early BoNT application may reduce muscle hyperactivity, delay the formation of dynamic wrinkles, and minimize the development of static lines over time. Histological studies indicate a potential remodeling effect on dermal collagen. However, data remain heterogeneous, and long-term safety and efficacy outcomes are not yet fully established. Conclusion: Preventive BoNT injections represent a promising tool in the proactive management of facial aging. Further longitudinal, high-quality studies are needed to substantiate its role within evidence-based aesthetic protocols.

Muscles doi: 10.3390/muscles4030030

Authors: Can Eser Türker Bıyıklı Paul J. Byrne John D. Duggan Joseph I. Esformes Jeremy A. Moody

This systematic review and meta-analysis was conducted to evaluate the effectiveness of the FIFA 11+ injury prevention programme, a neuromuscular training intervention involving muscular strength, proprioception, balance, and plyometric exercises, in reducing ankle injury incidence among football players. Included are randomised controlled trials (RCTs) involving players of any age, sex, or competition level, comparing the FIFA 11+ programme with standard warm-up routines. Studies were eligible if they had a minimum follow-up of five months and reported at least two of the following: number of ankle injuries, incidence rate, and exposure hours. Searches were conducted in PubMed, MEDLINE (via OVID), Scopus, and SPORTDiscus up to October 2024. Risk of bias was assessed using the revised Cochrane Risk of Bias tool (RoB 2), and a random-effects meta-analysis was conducted. Three RCTs, involving 3833 participants and 286,827 exposure hours, met the inclusion criteria. The pooled analysis showed that the FIFA 11+ programme significantly reduced ankle injury rates compared to control groups (rate ratio (RR) = 0.67, 95% confidence interval (CI): 0.46–0.96, p = 0.03, I2 = 52%), reflecting a 33% lower risk. The certainty of the evidence was rated as moderate due to bias in two studies. In conclusion, the FIFA 11+ programme significantly reduces ankle injury incidence and supports implementation at all levels. However, further research is needed to examine long-term effects, optimal doses, and applicability across diverse football populations.

Muscles doi: 10.3390/muscles4030029

Authors: Mario Spirito

This work investigates the macroscopic behavior of skeletal muscles from a system-theoretic perspective. Based on data available in the literature, we propose an initial evaluation model for isometric force generation, i.e., force produced at a constant muscle length or in quasi-static conditions, as a function of muscle length and neuronal excitation frequency. This model enables a more physics-inspired representation of isometric force by employing a nonlinear spring framework with controllable properties such as stiffness and rest length. Finally, we introduce a hybrid dynamical filter model to describe components of the sensory system responsible for relaying information about muscle length and its rate of change back to the Central Nervous System. As an application case, we present the modeling of the oculomotor system, highlighting the relevance of the proposed modeling approach in a physiologically meaningful control task.

Muscles doi: 10.3390/muscles4030028

Authors: Georgios Sidiropoulos Nikolaos Strimpakos Asimakis K. Kanellopoulos Maria Tsekoura Konstantinos Alexiou Olympia Papakonstantinou Zacharias Dimitriadis

Background: The reliable assessment of cervical muscle morphology is essential for both clinical and research use. However, evidence on the reliability of ultrasound measurements remains limited. Objective: To investigate the intra-rater and test–retest reliability of morphological measurements of the Longus Colli, Sternocleidomastoid, Multifidus Cervicis, and Semispinalis Capitis muscles using musculoskeletal ultrasound. Methods: Cross-sectional area, anteroposterior, and lateral dimensions were assessed using B-mode ultrasound. Anterior neck muscles were scanned in the supine position, while posterior neck muscles were scanned in the prone position. Each muscle was measured three times (to assess intra-rater reliability), which was repeated after 30 min (to assess test–retest reliability). Measurements were also normalized according to BMI and neck circumference. Results: Intra-rater reliability was found to be good to excellent for the Longus Colli (ICC = 0.77–0.92), excellent for the Sternocleidomastoid (ICC = 0.93–0.99), good to excellent for the Semispinalis Capitis (ICC = 0.89–0.97), and moderate to excellent for the Multifidus Cervicis (ICC = 0.69–0.92). Test–retest reliability was found to be moderate to good for the Longus Colli (ICC = 0.73–0.87), good to excellent for the Sternocleidomastoid (ICC = 0.84–0.98), good to excellent for the Semispinalis Capitis (ICC = 0.78–0.95), and good to excellent for the Multifidus Cervicis (ICC = 0.80–0.92). Conclusions: Musculoskeletal ultrasound demonstrates strong reliability for cervical muscle assessment, supporting its clinical use.

Muscles doi: 10.3390/muscles4030027

Authors: Sofia Sgourda Maria Loulla Eirini Zisiopoulou Krystalia Katsiou Sofia Nikolaidi Ioannis Kyrosis Anna Christakou

Chronic musculoskeletal pain negatively affects patients’ quality of life, and pain perceptions may significantly influence rehabilitation outcomes. This study investigated the relationships among pain intensity, pain perceptions, and kinesiophobia in individuals with chronic musculoskeletal pain. No previous studies have examined these variables in combination. A cross-sectional observational study was conducted with 37 participants with non-specific chronic musculoskeletal pain for at least 6 months, affecting the neck (n = 8), lower back (n = 18), upper limbs (n = 5), lower limbs (n = 5), or shoulder (n = 1). The following validated tools were used: (a) Pain Beliefs and Perceptions Inventory (PBPI), (b) the Tampa Scale for Kinesiophobia (TSK), and (c) the Short-Form McGill Pain Questionnaire (SF-MPQ). Spearman r correlation analyses were performed. Total kinesiophobia scores were positively correlated with (a) total pain intensity (McGill score) (r = 0.37, p = 0.022), (b) present pain intensity (PPI) (r = 0.52, p = 0.001), (c) pain duration (r = 0.51, p = 0.001), (d) the “mystery” factor of pain perception (r = 0.41, p = 0.013), and (e) the Visual Analogue Scale (VAS) (r = 0.42, p = 0.009). The total pain perception scores were positively associated with the “fear of injury” factor of kinesiophobia (r = 0.36, p = 0.028). The McGill pain scores were strongly correlated with both PPI (r = 0.63, p = 0.001) and VAS (r = 0.51, p = 0.001). There is a significant relationship between pain perception and kinesiophobia levels in patients with chronic musculoskeletal pain. Limitations of the study include a small and heterogeneous sample regarding pain localization. Further research is required using larger, more homogeneous populations to confirm the present findings.

Muscles doi: 10.3390/muscles4030026

Authors: Jialin Fan Zara Khanzada Yunpeng Xu

Skeletal muscle aging and related diseases are characterized by progressive loss of muscle mass, strength, and metabolic function. Central to these processes is mitochondrial dysfunction, which impairs energy metabolism, redox homeostasis, and proteostasis. In addition, non-mitochondrial factors such as muscle stem cell exhaustion, neuromuscular junction remodeling, and chronic inflammation also contribute significantly to muscle degeneration. This review integrates recent advances in understanding mitochondrial and non-mitochondrial mechanisms underlying muscle aging and disease. Additionally, we discuss emerging therapeutic approaches targeting these pathways to preserve muscle health and promote healthy aging.

Muscles doi: 10.3390/muscles4030025

Authors: Clara Lépée-Aragón Irune García Alicia Aurora Rodríguez Corrado Angelini Oscar Martínez

Limb–girdle muscular dystrophy (LGMD) encompasses a heterogeneous group disease, genetic and phenotypically. There are more than 30 subtypes divided into two groups: autosomal dominant and recessive. LGMDs are characterised by muscle weakness; however, psychosocial factors seem to be affected too, such as HRQoL. Given the lack of literature in this respect, the present cross-sectional study aimed to create a patient profile comparing both dominant and recessive forms by analysing HRQoL through the INQoL, and sociodemographic data. The LGMD-recessive group had a worse HRQoL compared to the dominant group, specifically in the dimensions of muscle weakness (p = 0.007), emotion (p = 0.046), independence (p = 0.029), and body image (p = 0.022). In addition, in the LGMD-dominant group, 77.9% of the relational indicator was explained by age (B = 0.907, p = 0.012), which can be understood as a limitation in their social role due to the disease progression. In contrast, no sociodemographic variables were found to be predictive of the HRQoL of patients with recessive forms of LGMD. These results are relevant for clinical practice, as they reflect the most affected areas of HRQoL in LGMD patients, differentiating between recessive and dominant forms.

Muscles doi: 10.3390/muscles4030024

Authors: João Francisco Ferreira Ricardo Maia Ferreira Filipe Maia Luís Gonçalves Fernandes César Leão Nuno Pimenta

Ergogenic supplements are becoming increasingly popular in the diet of trained individuals, due to their potential benefits. Ashwagandha (Withania somnifera) is one of the supplements that has recently grown in popularity. Despite growing interest, its scientific background remains limited and sometimes inconsistent. Objective: This overview of systematic reviews aimed to evaluate the effects of Ashwagandha supplementation on sports performance and health-related outcomes. Methods: A systematic literature search was carried out on the following electronic databases: PUBMed, Scopus, Academic Search Complete, SPORTDiscus, Web of Science, and Google Scholar, using the search terms “ashwagandha” and “systematic review” in the title or abstract of the publication in July 2024. The eligibility of the articles was assessed using the PICOS (Population, Intervention, Comparator, Outcomes, and Study Design) approach, and risk of bias was assessed using the AMSTAR-2 checklist. Results: Of the 2388 systematic reviews found, 11 met the inclusion criteria, which included 151 original studies representing 9005 individuals. Findings suggest that Ashwagandha supplementation may improve various aspects of sports performance, such as endurance and muscular strength, as well as health-related outcomes, including anxiety reduction, improved sleep quality, and enhanced sexual function. The most commonly used doses of Ashwagandha supplementation are between 500 mg and 1000 mg a day. Conclusion: While current evidence indicates promising effects of Ashwagandha on physical and psychological parameters, further high-quality randomized controlled trials are needed. Therefore, its use in athletes or healthy individuals should be considered with caution and based on individual needs.

Muscles doi: 10.3390/muscles4030023

Authors: Jack Fahey Paul Comfort Nicholas Joel Ripley

Background: Expression of maximal and rapid force in the hip, knee, and plantar flexors is important for athletic performance in female soccer. This study was designed to determine the effect of relative isometric strength in the isometric mid-thigh pull (IMTP) on countermovement jump (CMJ) and rebound jump (CMJ-R) performance in female youth soccer players. Methods: Ninety-six female soccer players (age: 14.1 ± 2.3 years, height: 160.5 ± 9.7 cm, mass: 55.0 ± 10.3 kg) completed three trials of the IMTP, CMJ, and CMJ-R using force plates. Players were categorized as stronger (top quartile, n = 19) and weaker players (bottom quartile, n = 23) based on IMTP relative net peak force. One-way Bayesian independent t-tests were performed between stronger and weaker players. Results: Very large difference in lower limb strength between groups (g = 5.05). Moderate to very strong evidence to support that stronger players had greater countermovement depth and time to take-off with similar jump heights than weaker players. Strong evidence was observed for CMJ-R height, with stronger players falling from a greater height and executing similar ground contact times compared to weaker players. Conclusions: Relative strength has implications for CMJ-R, highlighting the importance of developing relative strength in hip, knee, and plantar extensors.

Muscles doi: 10.3390/muscles4030022

Authors: Elisa Duranti

Amyotrophic lateral sclerosis (ALS) is a progressive disease that degeneratively damages both upper and lower motor neurons, eventually resulting in muscular paralysis and death. Although ALS is broad in scope and commonly thought of as a motor neuron disease, more active research sheds light on the that role skeletal muscle plays in the development and progression of the disease. Muscle tissue in ALS patients and in animal models demonstrates severe regenerative deficits, including impaired myogenesis and impaired myoblast fusion. In ALS, muscle stem cells, known as satellite cells, show poor performance in activation, proliferation, and differentiation and thus contribute to ALS muscle wasting. Moreover, the pathological tissue environment that inhibits myoblast fusion is made up of proinflammatory cytokines, oxidative stress, and a lack of trophic signals from the neuromuscular junction, which greatly disrupts homeostatic regulation. It is likely that skeletal muscle is instead a dynamic player, fueling neuromuscular degeneration as opposed to a passive responder to denervation. One must appreciate the cellular and molecular changes that complicate muscle regeneration in ALS for effective treatment to be developed, permitting simultaneous interventions with both muscle and neurons.

Muscles doi: 10.3390/muscles4030021

Authors: Alejandro Caña-Pino María Dolores Apolo-Arenas

Service-Learning (SL) is an innovative educational methodology that integrates academic learning with active community engagement, fostering both technical and transversal competencies. This pilot study explores the implementation of an SL-based experience within the Physiotherapy Degree at the University of Extremadura. The primary objective was to design and deliver therapeutic exercise programs targeting patients with cardiorespiratory conditions, utilizing local community resources. A total of 44 third-year physiotherapy students participated in the design and simulated the implementation of community-based interventions targeting muscular strength, postural control, balance, and endurance. A mixed-methods approach was used, combining descriptive statistics (SPSS v23) and thematic analysis of student reflections to assess the impact of SL on the development of specific professional competencies, including clinical reasoning, patient communication, therapeutic planning, and adaptation of interventions to diverse environments. The results show a significant improvement in students’ theoretical and practical understanding, with over 70% of participants rating their learning experience between 8 and 10 (on a 0–10 scale) in aspects such as pathology description, clinical assessment, and exercise planning. Additionally, 92% reported improved teamwork, 89% noted better adaptability, and 87% reported enhanced decision-making skills. The findings suggest that SL can enhance perceived learning in musculoskeletal rehabilitation and support the transition from academic training to clinical practice. However, the study is exploratory and based on perceived outcomes, and future research should include validated tools and real patients to assess its impact more rigorously. This pilot study highlights the value of integrating musculoskeletal-focused training—targeting strength, balance, and endurance—into physiotherapy education through Service-Learning methodology. The study highlights SL’s potential to enrich physiotherapy education while leveraging community spaces—such as those in Extremadura, a region with three UNESCO World Heritage Sites—as dynamic learning environments.

Muscles doi: 10.3390/muscles4030020

Authors: Esther Hernández Rovira Diego A. Alonso-Aubin Dolors Cañabate Ortiz Carlota Torrents Martín Tamara Rial Rebullido

This study aimed to describe and compare the serratus anterior (SA) and latissimus dorsi (LD) muscle activity during six hypopressive exercise (HE) positions performed in open and closed kinetic chains. While previous studies analyzed abdominal and pelvic muscle activity during HE, research on scapular stabilizers like SA and LD remains underreported. Twenty-five healthy adults (mean age, 42.9 ± 8.4 years; BMI, 22.1 ± 2.4 kg/m2) with prior HE experience performed three open and three closed-chain HE positions. Surface electromyography recorded bilateral SA and LD activity, normalized to maximum voluntary isometric contraction (MVIC). SA showed greater activation than LD across all positions, with moderate activation levels (20–40% MVIC), while LD activation remained mild (<20% MVIC). Significant differences were found across positions and kinetic chain conditions. SA activation was higher during closed-chain standing (W = 41; p < 0.001; r = −0.74) and kneeling (W = 9; p < 0.001; r = −0.94), while LD activity increased significantly in the seated closed-chain position (left LD: W = 26; p < 0.001; r = −0.84; right LD: W = 20; p < 0.001; r = −0.87). These findings suggest body and kinetic chain positioning influence scapular muscle recruitment during HE. Further research is warranted to determine clinical applications.

Muscles doi: 10.3390/muscles4020019

Authors: Josh B. Landers Korben R. Landers Nicholas G. Young

Blood flow restriction exercise (BFRE), which partially restricts arterial inflow and occludes venous outflow to the limbs, has gained attention for its potential to elevate serum brain-derived neurotrophic factor (BDNF), a key mediator in the muscle–brain crosstalk leading to improvement of neuroplasticity, neurogenesis, and cognitive health. In this systematic review of five studies, participants included healthy young adults, older adults, and individuals with clinical conditions. Most investigations found that BFRE increased serum BDNF, with responses comparable to those elicited by high-intensity exercise. Proposed mechanisms center on the metabolic demands of BFRE, which may increase lactate and thereby trigger BDNF release. However, two studies showed no significant changes, possibly due to short exercise duration, insufficient training intensity, or age-related reductions in BDNF responsiveness. The small sample sizes and varied protocols across studies limit definitive conclusions. Nonetheless, BFRE may provide a valuable alternative for populations who cannot tolerate high mechanical loads, and it shows promise for enhancing neurotrophic support and potentially improving brain health. Larger, well-controlled trials are warranted to refine BFRE protocols and better understand optimal strategies for increasing BDNF and supporting neuroplasticity.

Muscles doi: 10.3390/muscles4020018

Authors: Andrew Usher John Babraj

Boxing is a sport that has a high level of oxygen use within the Rectus Femoris muscle, with recovery between rounds important to subsequent performance. The study aimed to determine muscle oxygen use in male and female professional boxers in response to a repeated sprint stimulus. 10 male (age: 26 ± 5 years, height: 177 ± 4 cm, weight: 72 ± 6 kg) and 6 female (age: 29 ± 4 years, height: 173 ± 2 cm, weight: 73 ± 4 kg) professional boxers took part. Participants attended a single session where a Moxy near-infrared monitor was placed on the rectus femoris muscle of both legs. Participants completed 2 × 30 s Wingate-based sprint efforts with a 60 s active recovery (maintaining 60 rpm against 50 W resistance). Skeletal muscle oxygenation was recorded throughout. Significant differences were found in peak power, average speed and rate of fast desaturation between males and females (p < 0.001) in both sprints. There was a significant difference in males and females for the rate (sprint 1M: −5.6 ± 1.2%.s−1, 1F: −2.3 ± 1.9%.s−1, p < 0.05; sprint 2M: −4.2 ± 1.1%.s−1, 2F: −1.5 ± 0.9%.s−1, p < 0.05) and duration of fast desaturation (sprint 1M: 6.1 ± 1.3 s, 1F: 3.7 ± 2.8 s, p < 0.05; sprint 2M: 7.3 ± 1.6 s, 2F: 4.5 ± 1.0 s, p < 0.05) in both sprints. This study demonstrates that male professional boxers have a significantly different oxygen use and recovery in response to a high-intensity stimulus compared to female boxers. In both male and female boxers, the ability to perform subsequent high-intensity activity is dependent on the quality of the recovery from the initial high intensity activity. Therefore, there is a greater need to focus training to improve recovery kinetics in boxing.

Muscles doi: 10.3390/muscles4020017

Authors: Cian M. Walsh Joseph I. Esformes Jeremy A. Moody Paul J. Byrne

Background: Previous work has found that combining plyometric and resistance training in a single session can be effective in improving maximum strength (muscle contraction ability), vertical jumping, and sprint acceleration performance in young soccer players. However, the literature is scarce in relation to young rugby union players. Thus, the purposes of the present study were to examine the effects of a 6-week combined training (CT) programme that combined plyometric and resistance training in the same session on physical performance measures in adolescent male rugby union players and whether a 4-week period of plyometric training exclusion (Detraining) affects training adaptations. Methods: The participants (n = 15) completed a 6-week CT intervention and 4 weeks of plyometric detraining during the schoolboy rugby union in-season. A performance testing battery was conducted pre-intervention, post-intervention, and 4 weeks post-intervention. Results: A repeated measures ANOVA showed a significant effect for time on CMJ variables (mean power, mean force, and modified reactive strength index [RSI]), 3RM back squat strength, and 505 test time (p < 0.05). Pairwise comparisons revealed that CMJ variables (mean force, mean power, and peak power), 3RM back squat strength, and 505 test performance significantly increased from pre-intervention to post-intervention (p < 0.05). The 4-week plyometric detraining period significantly augmented CMJ variables (mean force, mean power, and modified RSI) and performance measures (standing broad jump [SBJ], 20 m sprint time, 505 test, and 3RM strength). Conclusions: The findings indicate that a 6-week CT programme can augment measures of lower-body power, maximal strength, and change of direction performance in adolescent male rugby union players, and a 4-week resistance training-only period (plyometric detraining) does not negatively affect performance adaptations.

Muscles doi: 10.3390/muscles4020016

Authors: Takumi Jiroumaru Shun Nomura Yutaro Hyodo Michio Wachi Junko Ochi Nobuko Shichiri Takamitsu Fujikawa

This study examined the impact of different breath-holding conditions on iliopsoas and other hip flexor muscle activity in individuals with chronic ankle instability (CAI). It has been hypothesised that impaired diaphragmatic function influences iliopsoas activation, potentially contributing to motor control deficits in patients with CAI. Eleven adults with a history of chronic ankle sprain participated in this study. Maximal isometric hip flexion was assessed under three breath-holding conditions: end-expiration, end-inspiration, and the intermediate state. Surface electromyography was used to record the muscle activity of the iliopsoas, rectus femoris, sartorius, and tensor fasciae latae, while the peak hip flexion torque was measured using an isokinetic dynamometer. Under the end-inspiration condition, iliopsoas activity on the affected side was significantly lower than that on the control side (p < 0.05). However, no significant differences were observed between the affected and control sides in the activity of the other hip flexor muscles or the peak hip flexion torque across breath-holding conditions. This study highlights the association between reduced iliopsoas activity during end-inspiration and compromised diaphragmatic function in patients with CAI. Future research should explore dynamic movement tasks and larger sample sizes to elucidate neuromuscular mechanisms further and refine rehabilitation strategies.

Muscles doi: 10.3390/muscles4020015

Authors: Ainize Elorduy-Terrado Gema Torres-Luque Krizia Radesca Guillermo Muñoz-Andradas Marisa Saenz-Bravo Diego Domínguez-Balmaseda

This systematic review aims to evaluate the impact of hormonal fluctuations during the menstrual cycle on the performance of female athletes. Methods: Following PRISMA guidelines, a comprehensive search was conducted in Scopus, Web of Science, and PubMed databases using the keywords: (“Menstrual cycle”) AND (“performance” OR “female athlete” OR “sport” AND NOT “male”); AND NOT (“contraceptive”). Inclusion criteria focused on original studies published between 2013 and 2023, in English or Spanish, involving eumenorrheic female athletes without menstrual disorders or oral contraceptive use. The studies were critically assessed using the McMaster scientific review method. Results: Thirteen eligible articles were reviewed, comprising a total sample of 152 athletes. Significant findings include increased flexibility during the ovulatory phase and enhanced aerobic and anaerobic capacities in the luteal phase. Additionally, the menstrual and premenstrual phases notably influenced aerobic and anaerobic capacities, performance perception, symptomatology, and exercise-induced muscle damage. Conclusion: Hormonal fluctuations can impact female athletes’ performance. However, further research is warranted due to inconsistent results stemming from variations in cycle phases studied, lack of standardized methodologies, small sample sizes, and short observation periods.

Muscles doi: 10.3390/muscles4020014

Authors: Quincy R. Johnson

The strength and conditioning literature examining neuromuscular physiology, bioenergetics, neuroendocrine factors, nutrition and metabolic factors, and the use of ergogenic aids, as well as physical and physiological responses and adaptations, have clearly identified the benefits of participating in regular resistance training programs for athletic populations, especially as it relates to improving muscular strength. Beyond evidence-based research, models for resistance training program implementation are of considerable value for optimizing athletic performance. In fact, several have been provided that address general to specific characteristics of athleticism (i.e., strength endurance, muscular strength, and muscular power) through resistance training over the decades. For instance, a published model known as the strength–endurance continuum that enhances dynamic correspondence (i.e., training specificity) in athletic populations by developing structural, metabolic, and neural capacities across a high-load, low-repetition and low-load, high-repetition range. Further models have been developed to enhance performance approaches (i.e., optimum performance training model) and outcomes (i.e., performance pyramid), even within specific populations, such as youth (i.e., youth physical development model). The ten, five, three, or 10-5-3 (TFT) model for strength and conditioning professionals synthesizes currently available information and provides a framework for the effective implementation of resistance training approaches to suit the needs of athletes at each stage of development. The model includes three key components to consider when designing strength and conditioning programs, denoted by the acronym TFT (ten, five, three). Over recent years, the model has gained much support from teams, coaches, and athletes, mainly due to the ability to streamline common knowledge within the field into an efficient and effective resistance training system. Furthermore, this model is distinctly unique from others as it prioritizes the development of strength–endurance, muscular strength, and muscular power concurrently. This paper explains the model itself and begins to provide recommendations for those interested in implementing TFT-based approaches, including a summary of points as a brief take-home guide to implementing TFT interventions. It is the author’s hope that this paper encourages other performance professionals to share their models to appreciate human ingenuity and advance our understanding of individualized approaches and systems towards the physical development of the modern-day athlete.