Search Results (89)

Objectives: The aim of this study was to evaluate the impact of four working heights on lumbar biomechanics during wall construction tasks, focusing on work-related musculoskeletal disorders (WMSDs). Methods: Fifteen young male participants performed simulated mortar-spreading and bricklaying tasks while actual body movements were recorded using Inertial Measurement Unit (IMU) sensors. Muscle activities of the lumbar erector spinae (ES), quadratus lumborum (QL), multifidus (MF), gluteus maximus (GM), and iliopsoas (IL) were estimated using a 3D musculoskeletal (MSK) model and measured via surface electromyography (sEMG). The analysis of variance (ANOVA) test was conducted to identify the significant differences in muscle activities across four working heights (i.e., foot, knee, waist, and shoulder). Results: Findings showed that working at foot-level height resulted in the highest muscle activity (7.6% to 40.6% increase), particularly in the ES and QL muscles, indicating an increased risk of WMSDs. The activities of the ES, MF, and GM muscles were statistically significant across both tasks and all working heights (p < 0.01). Conclusions: Both MSK and sEMG analyses indicated significantly lower muscle activities at knee and waist heights, suggesting these as the best working positions (47 cm to 107 cm) for minimizing the risk of WMSDs. Conversely, working at foot and shoulder heights was identified as a significant risk factor for WMSDs. Additionally, the similar trends observed between MSK simulations and sEMG data suggest that MSK modeling can effectively substitute for sEMG in future studies. These findings provide valuable insights into ergonomic work positioning to reduce WMSD risks among wall construction workers. Full article

Introduction: Hip abductor strength is essential for pelvic stability, lower limb alignment, and injury prevention. Weaknesses of the gluteus medius and minimus contribute to various musculoskeletal conditions. Lateral band walks and monster walks are elastic resistance exercises commonly used to target the hip abductors and external rotators in functional, weight-bearing tasks. Therefore, the aim was to summarize the current evidence on the biomechanics, muscle activation, and clinical applications of lateral and monster band walks. Methods: This narrative review was conducted following the SANRA guideline. A comprehensive literature search was performed across PubMed, Scopus, Web of Science, and SPORTDiscus up to April 2025. Studies on the biomechanics, electromyography, and clinical applications of lateral band walks and monster walks were included, alongside relevant evidence on hip abductor strengthening. Results: A total of 13 studies were included in the review, of which 4 specifically investigated lateral band walk and/or monster walk exercises. Lateral and monster walks elicit moderate to high activation of the gluteus medius and maximus, especially when performed with the band at the ankles or forefeet and in a semi-squat posture. This technique minimizes compensation from the tensor fasciae latae and promotes selective gluteal recruitment. Proper execution requires control of the trunk and pelvis, optimal squat depth, and consistent band tension. Anatomical factors (e.g., femoral torsion), sex differences, and postural variations may influence movement quality and necessitate tailored instruction. Full article

Background/Objectives: This study aims to investigate the effects of caffeinated chewing gum on maximal strength, muscular power, and neural drive to the prime movers during bench press and back squat in resistance-trained men. Methods: Sixteen resistance-trained males participated in a double-blind, randomized trial, chewing either caffeinated gum (4 mg/kg) or placebo gum on two separate occasions, seven days apart. After chewing for 5 min, participants performed a maximal strength test followed by muscular power assessments at 25%, 50%, 75%, and 90% of their one-repetition maximum (1RM), completing with 3, 2, 1, and 1 repetition (s), respectively, for bench press and back squat. Surface electromyography data were recorded for each repetition. Results: Caffeinated gum did not significantly improve one-repetition maximum (1RM) for bench press (p > 0.05), but increased mean frequency (MF) and median frequency (MDF) in anterior deltoid, pectoralis major, and biceps brachii (all p < 0.05) compared to placebo. For back squat, 1RM increased with caffeinated gum, along with higher MF and MDF in vastus medialis (all p < 0.05). Caffeinated gum also improved mean and peak velocities, and mean and peak power outputs at 25–75% 1RM during the bench press (all p < 0.05), along with elevated MDF in pectoralis major and biceps brachii (all p < 0.05). Similar improvements were seen in mean and peak velocities during the back squat at 25–90% 1RM (all p < 0.05), along with higher MF and MDF in vastus medialis and increased normalized root mean square activity in gluteus maximus (all p < 0.05). Conclusions: Caffeinated chewing gum (4 mg/kg) enhanced muscular power (25–75% 1RM) in the bench press and improved maximal strength and muscular power (25–90% 1RM) in the back squat by increasing muscle recruitment in resistance-trained men. Full article

Objectives: To comprehensively examine the association between spinopelvic alignment and muscle shortening in healthy young men, focusing on the individual and interactive effects of thoracic kyphosis, lumbar lordosis, and anterior pelvic tilt using SHapley Additive exPlanation (SHAP) analysis. Methods: Forty-one healthy young adult men participated in this cross-sectional study. Thoracic kyphosis, lumbar lordosis, and anterior pelvic tilt were measured using a flexible curve ruler and inclinometer. Muscle length indices for six muscles (iliopsoas, rectus femoris, gluteus maximus, hamstrings, back extensors, and abdominals) were assessed via standardized physical examinations and image analysis. A machine learning model was developed, and SHAP analysis applied to determine individual and interactive contributions of spinopelvic angles to each muscle length index. Results: SHAP analysis showed that hip-related muscle shortening (iliopsoas, rectus femoris, hamstrings, gluteus maximus) was influenced by both individual alignments and interactions, especially between thoracic kyphosis and lumbar lordosis. Lumbar lordosis was most associated with iliopsoas shortening (SHAP = −0.09), while anterior pelvic tilt was linked to hamstring shortening (SHAP = −0.30). Thoracic kyphosis was the key factor for rectus femoris shortening (SHAP = −0.05). Interactive effects exceeded individual contributions for the rectus femoris, gluteus maximus, and hamstrings. In contrast, spinal alignment had minimal influence on the back extensors and abdominals. Conclusions: Both individual and intersegmental spinal alignments are associated with muscle shortening, particularly in hip-related muscles. The interaction between thoracic kyphosis and lumbar lordosis plays a pivotal role. These findings underscore the importance of evaluating segmental spinal interactions when assessing muscle flexibility and posture. Full article

Background: Gluteal augmentation and reshaping have recently gained popularity due to growing patient demand. The rising number of intramuscular gluteal augmentation procedures has led to a corresponding increase in implants, although this has not reduced noticeable esthetic flaws and relatively common postoperative complications. The patient often opts for a secondary gluteal replacement implant. However, studies on this procedure are scarce. Methods: We describe our secondary submuscular gluteal implant replacement technique in patients complaining about dislocation or complications with the primary intramuscular gluteal implant. This procedure involved creating a new round implant pocket in a deeper anatomical plane while keeping the gluteus maximus muscle bridge that joins the intramuscular pocket with the submuscular pocket as intact as possible. To achieve this result, we describe the safest way to remove the intramuscular implant: a small incision is performed posterior to the iliac crest, through which the intramuscular gluteal implant is removed via a small intramuscular-subcutaneous tunnel. We reviewed surgical data, focusing on implant size choice and postoperative complications. Results: We performed this technique on 108 patients. The most frequent complications included three cases of laceration of the muscular bridge between the old intramuscular plane and the new submuscular pocket, resulting in both pockets merging, and eight cases with temporary nerve pain lasting a few days postoperatively. Conclusions: This study validates our approach for addressing and preventing dislocation or other complications from intramuscular gluteal augmentation procedures with implants by applying a safe technique that involves replacing the intramuscular implant with a submuscular one. Full article

Background: Femoroacetabular impingement (FAI) is a complex hip disorder characterized by abnormal contact between the femoral head and acetabulum, often leading to joint damage, chronic pain, and early-onset osteoarthritis. Despite MRI being the imaging modality of choice, diagnosis remains challenging due to subjective interpretation, lack of standardized imaging criteria, and difficulty differentiating symptomatic from asymptomatic cases. This study aimed to develop and externally validate radiomics-based machine learning (ML) models capable of classifying healthy, asymptomatic, and symptomatic FAI cases with high diagnostic accuracy and generalizability. Methods: A total of 82 hip MRI datasets (31 symptomatic, 31 asymptomatic, 20 healthy) from a single center were used for training and cross-validation. Radiomic features were extracted from four segmented anatomical regions (femur, acetabulum, gluteus medius, gluteus maximus). A four-step feature selection pipeline was implemented, followed by training 16 ML classifiers. External validation was conducted on a separate multi-center cohort of 185 symptomatic FAI cases acquired with heterogeneous MRI protocols. Results: The best-performing models achieved a cross-validation accuracy of up to 90.9% in distinguishing among healthy, asymptomatic, and symptomatic hips. External validation on the independent multi-center cohort demonstrated 100% accuracy in identifying symptomatic FAI cases. Since this metric reflects performance on symptomatic cases only, it should be interpreted as a detection rate (true positive rate) rather than overall multi-class accuracy. Gini index-based feature selection consistently outperformed F-statistic-based methods across all the models. Conclusions: This is the first study to systematically integrate radiomics and multiple ML models for FAI classification for these three phenotypes, trained on a single-center dataset and externally validated on multi-institutional MRI data. The demonstrated robustness and generalizability of radiomic features support their use in clinical workflows and future large-scale studies targeting standardized, data-driven FAI diagnosis. Full article

This study investigates differences in lower limb muscle activity during isometric external hip rotation while standing using static and dynamic models within the AnyBody Modeling System. Thirty-three participants performed controlled isometric rotations using a custom-designed device capable of simultaneously measuring rotational moments and ground reaction forces. Both static and dynamic simulations were conducted for each subject using personalized biomechanical models. Muscle activity values at the point of peak rotational moment were analyzed for twelve key muscles involved in hip rotation and stabilization of the knee joint, and statistical differences were assessed for significance. Muscles from the gluteal group (Gluteus minimus, medius, and maximus) generally showed lower activation in dynamic simulations, although this trend was not statistically significant for all muscles or test conditions. The mean difference in muscle activity values between static and dynamic simulations was between 0.03 and 0.08 for the gluteal group muscles and up to 0.15 for the Iliopsoas. Static models overestimated the role of stabilizers. Significant differences (p ≤ 0.05, Wilcoxon signed-rank test) were observed between the two approaches in terms of predicted muscle activation. In conclusion, discrepancies in muscle activity predictions between static and dynamic simulations highlight the need for task-specific simulation design and careful result interpretation. Full article

Background and Objectives: We conducted a retrospective observational study. Background: While traditional rehabilitation approaches emphasize trunk muscle conditioning, emerging evidence suggests that leg muscle strength plays a critical role in postoperative functional mobility. Previous studies have focused on trunk muscle rehabilitation in patients with adult spinal deformity (ASD). However, recent findings suggest that leg muscle conditioning may be a better predictor of postoperative improvement. Strengthening the gluteal and iliopsoas muscles has been linked to improved sagittal balance, gait stability, and mobility, ultimately leading to enhanced surgical outcomes. This study examines the relationship between the preoperative functional cross-sectional area (FCSA) of trunk and leg muscles and postoperative improvement in mobility, as assessed by the Timed Up and Go (TUG) test, in patients undergoing surgery for ASD. Materials and Methods: Sixty-two patients (57 women, mean age 71.2 ± 7.1 years) who underwent ASD surgery between April 2017 and April 2024 were retrospectively analyzed. The FCSA of key muscles—psoas major (PM), erector spinae (ES), multifidus (MF), gluteus maximus (GM), and gluteus medius (GMed)—was measured using CT images. Patients were categorized into an improvement group and a non-improvement group based on whether they achieved the minimum clinically important difference (MCID) of −2 s in the TUG test 12 months after surgery. Propensity score matching (PSM) was applied to adjust for baseline differences between the groups. A significance level of 5% was used for all comparisons. Results: Thirty-three patients achieved a clinically meaningful improvement in TUG, while 29 did not. Before PSM, patients with worse preoperative TUG and Oswestry Disability Index (ODI) scores showed greater improvements (p < 0.01). After PSM, no significant differences were found between the groups in terms of age, sex, or BMI. However, the improvement group showed significantly greater FCSA values in PM (6.1 ± 2.3 mm² vs. 3.9 ± 1.5 mm², p = 0.021) and GM (19.9 ± 5.9 mm² vs. 15.3 ± 3.9 mm², p = 0.019). Conclusions: This study demonstrates that leg muscle quality, particularly that of the gluteus maximus and psoas major, is a significant predictor of postoperative mobility improvement in patients with ASD. These findings challenge the conventional focus on trunk muscles and suggest the inclusion of leg muscle training in preoperative rehabilitation strategies to enhance surgical outcomes. Full article

Blood Flow Restriction Training (BFRT) is a training method typically performed with low-intensity loads, yet it has been shown to induce muscle growth and strength gains similar to those achieved through high-load resistance training. This study investigates how different cuff widths affect muscle activation and synergy during squat exercises under BFRT conditions, using wavelet packet transform combined with non-negative matrix factorization (WPT-NNMF) for time-frequency analysis of muscle synergy. Fifteen male participants, each with more than three years of resistance training experience, performed squats under three conditions: non-BFRT (Non-BFRT), BFRT with a 5 cm cuff (5 cm-BFRT), and BFRT with a 10 cm cuff (10 cm-BFRT), all at 30% of their one-repetition maximum (1RM). Surface electromyography (sEMG) signals were recorded from eight lower-limb muscles, and muscle synergy patterns were analyzed using NNMF and WPT-NNMF. The results showed that, compared to Non-BFRT, the 10 cm-BFRT condition significantly increased activation in the vastus lateralis (VL), gluteus maximus (GM), tibialis anterior (TA), and lateral gastrocnemius (GL), while the 5 cm-BFRT decreased activation in the biceps femoris (BF) and increased TA activation. Muscle synergy analysis revealed three distinct synergy modules across all conditions, with the total number of synergies remaining stable. However, the activation weights of muscles within these modules varied across different squat phases, suggesting adaptive neuromuscular regulation under different BFRT conditions. The time-frequency synergy analysis highlighted dynamic changes in muscle coordination across time scales and frequency bands under various training conditions. The number of muscle synergies showed significant changes across different time-frequency regions, with a marked decrease in the 120–250 Hz frequency range in the 5 cm-BFRT condition compared to Non-BFRT. This study is the first to apply time-frequency muscle synergy analysis to investigate the effects of cuff width on neuromuscular coordination during BFRT. The findings offer new insights into the time-frequency characteristics of muscle synergy under BFRT conditions and enhance the understanding of neuromuscular control and motor execution in blood flow restriction training. Full article

Objectives: This study aimed to compare hip abductor muscle composition and its age-related alterations between female patients with unilateral and bilateral osteoarthritis (OA) of the hip. Methods: This study enrolled 57 and 43 female patients with unilateral and bilateral advanced OA, respectively. Muscle composition of the glutei medius and minimus and the upper portion of the gluteus maximus was evaluated by computed tomography for planning unilateral total hip arthroplasty. The cross-sectional area ratio of the individual composition to the total muscle was calculated. Correlation coefficients were calculated to determine associations between age and muscle composition variables. Results: Comparison of hip abductor muscle composition between the affected and the contralateral sides in unilateral OA patients showed increased fatty infiltration in the muscles around the affected joint. Comparison of the composition around bilateral OA between the joint scheduled for operation and the contralateral joint demonstrated enhanced fatty infiltration in the glutei medius and minimus but no increase in the gluteus maximus around the operation-scheduled joint. Comparison of muscle composition between unilateral and bilateral OA demonstrated similar fatty infiltration around the operation-scheduled joint whereas there was increased fatty infiltration around the contralateral joint of bilateral OA. Significant association was found between age and hip abductor muscle composition around both sides of unilateral OA. However, there was no association between age and hip abductor muscle composition around both sides of bilateral OA. Conclusions: There were significant differences in hip abductor muscle composition and its age-related alterations between female patients with unilateral and bilateral OA. Full article

Ultrasound-guided botulinum toxin type A (BoNT-A) injections have become an essential tool in the management of lower limb spasticity. Following our previous work, which focused on upper limb muscles, this third part provides a detailed visual guide to the identification and injection of proximal lower limb muscles frequently involved in spastic gait and posture disorders. This guide presents the ultrasound anatomy, clinical relevance, and injection strategies for eleven key muscles: gluteus maximus, piriformis, psoas major, rectus femoris, sartorius, gracilis, adductor longus, adductor magnus, semimembranosus, semitendinosus, and biceps femoris. For each muscle, the Elias University Hospital (EUH) model is applied, highlighting the zones of maximum thickness and motor point density to ensure precise and effective BoNT-A delivery. Enhanced with high-resolution ultrasound images and dynamic scanning techniques, this visual guide supports clinicians in performing safe, targeted injections. It serves as both an educational and practical reference for the ultrasound-guided treatment of spasticity in the proximal lower limb, completing the series and offering a standardized framework for comprehensive BoNT-A management. By promoting accurate toxin delivery, this approach is expected to improve functional mobility, reduce spasticity-related complications, and optimize patient-centered outcomes in rehabilitation settings. Full article

With the global increase in women’s participation in running, understanding factors like footwear in performance and injury prevention has become essential. Minimalist shoes (MSs) and traditional shoes (TSs) influence muscle activation patterns, affecting running technique. Proper coordination of the core muscles is essential for efficient stride and posture. This study analyzed muscle activation in nulliparous women running in MSs and TSs at different speeds and explored the correlations with age and BMI. A crossover clinical trial assessed the EMG activation of the lumbar erector (LE), gluteus maximus (GM), pelvic floor, and internal oblique (IO) muscles during treadmill running at 6, 9, and 11 km/h. Fifty-one healthy women (26.55 ± 5.11 years; body mass index (BMI): 21.29 ± 2.07 kg/m²) participated. The protocol included a warm-up, 30 s runs at each speed, and a 5-minute washout between trials. The statistical analyses included Wilcoxon, Friedman, and Spearman’s correlation tests. GM and IO showed the highest activation (p < 0.001) regardless of the footwear or speed. No significant differences were found between MSs and TSs. Weak-to-moderate correlations emerged between BMI and LE muscle activation with MSs, and between BMI and IO with both footwear. Significant correlations were also found with IO activations, but none with PF muscles. The correlations between personal variables, shoe types, and muscle activation suggest that individual and external factors may influence neuromuscular modulation, impacting injury prevention and personalized interventions. Full article

Background: Previous research has examined the acute effects of high-intensity exercise on muscle contractility, revealing potential interference in reaching peak contraction. This study aims to evaluate the impact of a standardized kettlebell swing protocol on low back musculature contractility, measured by tensiomyography (TMG), and pain sensitivity, measured by pressure algometry. Methods: Forty participants were randomly assigned to one of three groups: control, kettlebell swing, and kettlebell isometric hold. Pre-intervention TMG and pressure pain threshold (PPT) measurements were taken, followed by the intervention and post-intervention measurements. Results: Participants averaged 23.85 years (SD ± 2.73), 162.39 lbs (SD ± 28.69), and 174.29 cm (SD ± 12.45). Baseline ANOVAs showed no significant differences between groups for pre-intervention DM or PPT measurements, nor for demographics (p > 0.05). Although no significant within-group differences in TMG measurements were observed, the kettlebell swing group showed small mean differences in muscle displacement and contraction time for the gluteus maximus with effect sizes ranging from 0.09 to 0.49. Conclusions: The study suggests posterior chain muscles, such as the gluteus maximus, are involved in kettlebell swings. Also, despite the lack of significant TMG differences within groups, the kettlebell swing group exhibited small changes in muscle characteristics, enhancing the understanding of exercise-induced hypoalgesia and posterior chain involvement in resistance exercises. Full article

This meta-analysis investigated muscle activity and sprint biomechanics by reviewing EMG, kinematic, and kinetic studies, with a focus on changes across sprint phases and the effects of fatigue. Following PRISMA 2020 guidelines, twelve studies were selected from databases such as PubMed and Scopus, analyzing lower limb muscles (e.g., biceps femoris, semitendinosus, gluteus maximus) and biomechanical variables like step length, stride frequency, and ground reaction forces. Using random-effects models and meta-regression, the analysis revealed that increased sprint speed is associated with greater activation of the posterior thigh muscles and gluteus maximus. The biceps femoris peaks in the late swing phase (~110% MVC), while the gluteus maximus is most active in early stance. Sprinting faster typically results in a 15–20% increase in step length and moderate changes in stride frequency. Fatigue causes earlier muscle activation, reduced hip and knee flexion, and longer ground contact times, which may impair efficiency and raise injury risk. A strong linear relationship (R² = 0.881, p < 0.001) was found between sprint speed and muscle activation, with activation increasing by ~6.3% MVC per 1 m/s. These findings highlight the importance of hamstring and gluteal strength, as well as fatigue resistance, in sprint training and injury prevention. Full article

Background/Objectives: Hip abductor weakness is a common issue in patients with lower back pain, knee osteoarthritis, and hip disorders, and compromises pelvic stability, gait control, and function. Side-lying hip abduction exercises are widely used as safe and effective interventions for patients unable to perform high-load or weight-bearing activities. However, the influence of ankle joint angles and distal muscle activity on the hip abductor muscles remains unclear. This study aimed to investigate the effects of ankle joint angles and activation states on unilateral right hip abductor strength and muscle activity. Methods: Fifteen healthy male adults (29.1 ± 5.4 years) participated. Surface electromyography (EMG) was used to measure the activity of the tensor fasciae latae (TFL), gluteus medius (G-med), gluteus maximus, tibialis anterior, and medial gas-trocnemius muscles. Hip abduction strength was evaluated in a side-lying position with the ankle positioned at three angles (neutral, dorsiflexion, and plantarflexion) and in three activation states (no activation, maximal dorsiflexion, and maximal plantarflexion). Two-factor (3 × 3) repeated measures ANOVA was used to analyze strength and EMG activity. Results: ANOVA revealed a significant interaction effect. The results of the simple main effects showed significantly higher hip abduction strength in dorsiflexion than in the neutral position and plantarflexion (p < 0.001). TFL and G-med EMG activities peaked during dorsiflexion, particularly under maximal dorsiflexion. Conclusions: These findings suggest that dorsiflexion enhances hip abductor strength and activity by increasing fascial tension (lateral line and superficial backline) and improving limb alignment. This approach may provide effective rehabilitation strategies. This is a load-adjustable training recovery approach that should be confirmed with future intervention studies. Full article