Search Results (149)

Background/Objectives: While strength training interventions improve walking performance in stroke survivors, the underlying neuromuscular mechanisms remain poorly understood. This study investigated muscle-level adaptations following a 12-week moderate-to-high-intensity strength training program in ten chronic stroke survivors using comprehensive musculoskeletal modeling analysis. Methods: Three-dimensional gait analysis was performed pre- and post-intervention, with subject-specific OpenSim models estimating individual muscle forces, powers, and work capacities throughout stance phase. Results: Non-paretic hip flexor negative work capacity increased significantly (0.033 to 0.042 J/kg, p = 0.033, Cohen’s d = 0.47), driven by enhanced rectus femoris power absorption during late stance that mechanistically facilitated trunk acceleration through leg deceleration. Knee extensor force generation showed increasing trends during loading response in both limbs. During push-off, ankle plantar flexor force generation showed trends toward bilateral improvements, primarily through paretic soleus and gastrocnemius contributions, though power output remained unchanged, indicating persistent velocity-dependent muscular deficits. Conclusions: Improved gait performance in both limbs demonstrates that strength training produces functionally beneficial bilateral muscle-level reorganization. The absence of a control group limits causal inference, though the observed biomechanical adaptations align with functional improvements, supporting the integration of strength training into comprehensive stroke rehabilitation protocols targeting locomotor recovery. Full article

Approximately two-thirds of athletes who are submitted to Anterior Cruciate Ligament Reconstruction (ACLR) never return to their preinjury level of performance, potentially due to muscle strength deficiencies or altered loading patterns during landing or jumping tasks. This study aimed to estimate individual muscle forces during a double-leg drop jump task, and assess sagittal plane between-limb asymmetries in muscle forces and ground reaction forces using a musculoskeletal modelling approach, in athletes who underwent ACLR. Thirty male field-sport athletes (age: 18–35 years; mass: 84.3 ± 12.3 kg; height: 180.2 ± 8.4 cm) post-ACLR (39.8 ± 3.9 weeks) using patellar or quadriceps tendon grafts were tested. Scaled musculoskeletal models were implemented in OpenSim, and muscle forces were estimated using the Computed Muscle Control optimization method. The contralateral limb exhibited greater vertical ground reaction forces across most of the rebound phase (d = 2.01). Compared with the contralateral limb, the ACLR limb showed reduced quadriceps (d = 1.72), soleus (d = 0.95), and gluteus maximus (d = 0.83) forces, indicating deficits in knee extensor, plantarflexor, and hip extensor neuromuscular function. Smaller asymmetries were found for the gluteus medius (d = 0.60) and hamstrings (d = 0.72), while other muscles showed symmetrical activation patterns. These results reveal persistent between-limb asymmetries in muscle recruitment and loading up to nine months post-ACLR, emphasizing the importance of targeted rehabilitation to restore symmetrical neuromuscular control during explosive movements. Full article

The primary purpose of this study was to examine the acute effects of a multi-ingredient preworkout supplement (MIPS) on isometric, concentric, and eccentric peak torque and electromyographic (EMG) responses of the leg extensors during a fatiguing isokinetic protocol. Thirteen male subjects (mean age ± SD = 22.9 ± 2.2 years) were assigned in crossover fashion to ingest an MIPS or placebo before an isokinetic protocol that consisted of 30 maximal, concentric and eccentric muscle actions with EMG signals recorded from the vastus lateralis, rectus femoris, and vastus medialis muscles. Immediately before (PRE) and after (POST) the isokinetic fatigue protocol, subjects were assessed for isometric peak torque. The MIPS condition resulted in greater isometric (205 ± 48 vs. 185 ± 44 N·m, p = 0.04) and concentric (121 ± 34 vs. 103 ± 27 N·m, p = 0.015) torque values versus placebo (collapsed across time). For eccentric peak torque as well as EMG amplitude and frequency values, there were no significant (p > 0.05) interactions or main effects for each condition. These findings indicated that acute ingestion of the MIPS enhanced isometric and concentric peak torque of the leg extensors, which was not explained by changes in the EMG signal. Full article

Background: Sarcopenia, characterized by loss of muscle mass, strength, and function, reduces independence and quality of life in older adults. Strength exercise (STR) mitigates these age-related declines, but evidence of short-term effectiveness remains limited. This study aimed to evaluate the effects of eight weeks of STR on body composition, muscle strength, and psycho-emotional state in community-dwelling elderly women. Methods: A prospective, controlled, non-randomized study included 44 women assigned to an STR (n = 20) or control (CON, n = 22) group. The STR group performed supervised exercise twice weekly for eight weeks. The outcomes were body composition, handgrip strength (HGS), quadriceps (Q) and hamstrings (H) strength, and perceived stress (PSS-10), assessed at baseline and after intervention. Within-group changes were analyzed using paired t-tests, and between-group differences were evaluated using analysis of covariance (ANCOVA) adjusted for baseline values. Results: After baseline adjustment, body mass (p = 0.041, partial η² = 0.103), BMI (body mass index, p = 0.030, partial η² = 0.115), and body fat percentage (p = 0.047, partial η² = 0.098) were significantly reduced in the STR group. Significant improvements were observed for H strength in both legs (p < 0.05, partial η² = 0.128–0.131), right HGS (p = 0.025, partial η² = 0.122), right HGS:BMI ratio (p = 0.013, partial η² = 0.150), and H:Q ratios on both sides (p < 0.05, partial η² = 0.109–0.118). No significant differences were observed for left-hand grip strength, knee extensor strength, or other body composition variables (p > 0.05). The perceived stress scores were significantly lower in the STR group post-intervention (p = 0.036, partial η² = 0.108). Conclusions: An eight-week supervised strength exercise program was associated with favorable changes in muscle strength, body composition, and psycho-emotional state in elderly women. Full article

Whole-body electromyostimulation (WB-EMS) is a time-efficient, joint-friendly, and highly customizable training technology that particularly attracts sportspeople and athletes looking to enhance performance, accelerate regeneration, and prevent injuries with WB-EMS. Based on a systematic review of the literature, the present evidence map aimed to provide an overview of outcomes addressed by WB-EMS in exercising cohorts of different levels. In summary, the search identified 34 research projects with 39 studies and 43 publications that addressed 79 outcome categories (e.g., isometric strength) with more than 300 single outcomes (e.g., isometric strength of leg extensors). Thirty-one studies focused on performance-related outcomes, four studies addressed regeneration-related outcomes, and eight studies reported outcomes related to anthropometry. A further 14 studies reported health- and safety-related outcomes. Twenty-five of the 31 studies that reported performance parameters addressed strength, ten power, 18 jumping, ten sprinting, six agility, six endurance, five anaerobic power, and one each flexibility or balance, and five studies reported sport-specific performance outcomes (e.g., shot velocity). Apart from outcomes concerning injury prevention or sport-specific complaints, there are in particular evidence gaps relating to the acute effects of WB-EMS on regeneration, particularly with respect to muscle recovery. Semiprofessionals/professionals were rarely addressed, and if so, primarily cohorts from team sports were evaluated, while no study focused on elite strength, endurance, or precision sports athletes. Full article

This study compared the body composition and strength of the lower extremity parameters between novice runners (NRs) and amateur marathon runners (AMRs). A total of 50 NRs (33.84 ± 4.32 years) and 50 AMRs (33.36 ± 5.55 years) were analyzed cross-sectionally. Bioelectrical impedance analysis measured body composition parameters, and isokinetic testing assessed knee muscle strength. The results showed that compared to AMRs, NRs had lower fat-free mass (FFM), skeletal muscle mass (SMM), and total body water (TBW) (−15, −12, and −5%; all p < 0.01) but higher body fat percentage (PBF) and visceral fat area (VFA) (+27 and +32%; both p < 0.01). They also had 6% lower knee extensor (KE) strength and 31% lower knee flexor (KF) strength on the dominant legs (DLs) and 14% lower KF strength on the non-dominant legs (NDLs). In addition, their hamstring–quadriceps ratio (H: Q) was 24% lower on the DLs and 9% lower on the NDLs. The NRs exhibited significant negative correlations between PBF, VFA, and knee muscle strength (r = −0.54 to −0.42, p < 0.01), while the AMRs had significant negative correlations only for PBF (r = −0.59 to −0.57, p < 0.001). In conclusion, the NRs exhibited lower FFM and TBW, higher PBF and VFA, and reduced muscle strength. In contrast, the AMRs exhibited the opposite pattern. These findings suggest that NRs with elevated body fat (BF) indicators should prioritize fat reduction and performance enhancement, while those with lower muscle mass require targeted programs to increase muscle capacity and joint stability. This approach may advance them toward the level of AMRs. Future studies should adopt longitudinal designs to explore how training interventions influence the physiological adaptations observed in runners at different experience levels. Full article

Background: Movement symmetry in the lower limbs is critical for biomechanical efficiency, injury prevention, and athletic performance. Lateral (sideways) jumping challenges force production and control in the frontal plane and provide a unique assessment of neuromuscular coordination that may not be detected through sagittal-plane tasks such as running or vertical jumping. This study aimed to evaluate limb asymmetries in isometric knee muscle torque and ground reaction forces (GRFs) during lateral jumps in healthy young women, using the Symmetry Index (SI) to quantify differences between limbs. Methods: Twenty right-limb dominant females (mean age: 20.65 ± 4.51 years) participated in the study. Isometric torque of the knee flexors and extensors was measured using a dynamometric testing station. Lateral jumps were performed onto dual force platforms, with GRF components (vertical (PD), anterior–posterior (AP), mediolateral (ML)) recorded separately for rightward and leftward jumps. SI was calculated for all parameters to determine side-to-side asymmetries, and paired Student’s t-tests were used for statistical comparisons. Results: Right-limb dominance was evident in both knee flexor and extensor torque. Significant asymmetries were observed across all GRF components, varying with jump direction. The trailing limb in each jump direction typically generated greater propulsion forces. In lateral jumps, the trailing limb is generally the leg positioned opposite to the direction of travel, playing a primary role in generating propulsion and absorbing forces during take-off. SI values revealed both inter-individual variability and consistent direction-dependent asymmetry patterns. Conclusions: The or-posterior and vertical components, with greater loading on the dominant leg. Muscle torque measurements also revealed imbalances, with flexors showing more symmetry than extensors. These findings underline the importance of assessing load symmetry to prevent injury and guide rehabilitation. Full article

Background: Core stability is a cornerstone of optimum athletic performance, and its reduction is a risk factor for athletic injuries. Evidence has shown that core impairments can alter lower-limb mechanics through the kinetic chains. Additionally, plantar pressure can be influenced by proximal conditions, such as core muscle fatigue. Therefore, this study aimed to investigate the correlation between core endurance and plantar pressure distribution (PPD) during double-leg stance, single-leg stance, and single-leg squat positions in healthy male athletes. Methods: A total of 21 healthy male recreational athletes between 19 and 26 years of age volunteered to participate in this correlational study. The McGill core endurance test was used to measure the endurance of their core flexors, extensors, and lateral flexors. The participants’ PPD was evaluated using the Tekscan Mobile Mat pressure measurement system in three positions (double-leg stance, single-leg stance, and single-leg squat) for both the dominant and non-dominant feet. Results: There was a poor and insignificant correlation (p > 0.05) between the core flexors’, extensors’, and side flexors’ endurance and the peak and total PPD in all the tested positions for both the dominant and non-dominant feet. Conclusions: Core muscle endurance is neither a component that affects nor is affected by the PPD in this study population. Thus, the endurance of core flexors, extensors, and side flexors may not be considered in screening, examination, or intervention for the total and peak pressure during double-leg stance, single-leg stance, and single-leg squat positions for both the dominant and non-dominant feet in the study population. Further similar studies are warranted in various sports and during dynamic tasks to better understand the different dimensions of the studied relationship in athletes. Full article

Objectives: This study aimed to compare the involuntary stimulated neuromuscular response of thigh muscles in karate subgroups and non-athletes. We investigated whether karate training creates neuromuscular adaptations and if the synchronization of knee flexor and extensor muscles in karate practitioners is level-dependent. Methods: The study included 7 elite karate athletes (KE), 14 sub-elite karate athletes (KSE), 16 individuals with basic karate training (KB), and 14 non–athletes (NA). Tensiomyographic (TMG) measurements were obtained from the rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus muscles. Indexes of Intermuscular Synchronization (IIS) were calculated for contraction time (Tc), total contraction time (TcT), and rate of muscle tension development (RMTD) as variables for the observed muscles of a given muscle group (extensors of the dominant leg, flexors of the dominant leg, extensors of the non-dominant leg, and flexors of the non-dominant leg). Results: Statistically significant differences were observed in the intermuscular synchronization indexes between karate experience levels and non-athletes. Compared to non-athletes, elite (KE), sub-elite (KSE), and beginner karateka (KB) all demonstrated shorter contraction time indexes in dominant knee extensors (p = 0.042, 0.040, and 0.013, respectively). In the non-dominant flexors, KE exhibited significantly better synchronization than KSE (p = 0.001), KB (p = 0.033), and NA (p = 0.002). For the total contraction time index, both KSE and KB outperformed NA in dominant extensors (p = 0.023 and p = 0.008), while KE showed superiority in non-dominant extensors and flexors compared to all other groups (p-values ranging from 0.002 to 0.038). Significant RMTD differences were found in the dominant leg between KE and KSE (p = 0.036) and KE and KB (p = 0.001), as well as in the non-dominant leg between KE and KB (p = 0.011) and KE and NA (p = 0.025). These findings were accompanied by statistical powers exceeding 0.80 in most cases, underscoring the robustness of the observed differences. Conclusions: These findings highlight that muscle coordination patterns, as revealed through non-invasive TMG-based indexes, are sensitive to training level and laterality in karate practitioners. Importantly, elite athletes demonstrated more synchronized activation in key muscle groups, suggesting a neuromuscular adaptation specific to high-level combat sports. From a biomechanical perspective, improved intermuscular synchronization may reflect optimized neural strategies for stability, speed, and efficiency—key components in competitive karate. Thus, this method holds promise not only for performance diagnostics but also for refining individualized training strategies in combat sports and broader athletic contexts. Full article

Context: Intermittent fasting (IF) and calorie restriction (CR) have gained interest as dietary strategies due to their potential for weight loss and multiple metabolic benefits. These strategies are often accompanied by exercise in an attempt to improve body composition and physical performance. However, further research is crucial to understanding whether or not physical performance is affected by the expected weight loss and related body composition changes in individuals on IF and CR, even when exercise is combined. Objective: We aimed to systematically evaluate the effects of IF and CR on exercise performance and body composition in adults aged 18 to 65 years. Data Source: A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A systematic review was conducted up to April 2024 by searching electronic databases, including PubMed, Web of Science, and Scopus. There was no limit on publication dates. Data Extraction: The search explored the impact of IF and CR combined with exercise vs. exercise alone (control) on exercise performance outcomes: VO_2max, handgrip strength, bench press strength, knee extensor strength, leg press strength, countermovement jump (CMJ), 400 m walk test, and gait speed; body weight, body mass index (BMI), and body composition: fat-free mass (FFM), fat mass (FM), and body fat percentage (BFP). Analyses included calculation of weighted mean difference (WMD), standardized mean difference (SMD), and 95% confidence intervals (CIs) to assess outcomes. Data Analysis: The meta-analysis included a total of 35 studies, ranging from 4 to 52 weeks and involving 1266 participants. The results showed that IF (hypocaloric or eucaloric diet) and CR combined with exercise increased handgrip strength [WMD = 1.707 kg, p = 0.01] compared to exercise alone. Moreover, IF and CR combined with exercise did not significantly affect VO_2max [SMD = 0.005, p = 0.94], bench press strength [WMD = 0.377 kg, p = 0.778], knee extensor strength [WMD = −4.729 kg, p = 0.12], leg press strength [WMD = −2.874 kg, p = 0.415], countermovement jump [WMD = −0.226 cm, p = 0.80], 400 m walk test performance [WMD = −8.794 s, p = 0.06], or gait speed [WMD = 0.005 m/s, p = 0.82] compared to exercise alone. Moreover, IF and CR combined with exercise decreased body weight [WMD = −4.375 kg, p = 0.001], BMI [WMD = −1.194 kg·m⁻², p = 0.001], FFM [WMD = −1.653 kg, p = 0.001], FM [WMD = −2.858 kg, p = 0.001], BFP [WMD = −0.826%, p = 0.001] compared to exercise alone. Conclusions: IF (hypocaloric or eucaloric) and CR can be effectively integrated into exercise training without negatively impacting most measures of physical performance, while significantly enhancing weight loss and adiposity-related outcomes. The findings from this meta-analysis involving both athletes and non-athletes suggest that weight loss induced by IF and CR combined with exercise does not necessarily result in reduced physical performance. In real-world scenarios, however, different outcomes are conceivable, as body composition, physical capacity, diet and exercise can vary considerably based on individual conditions. Full article

Background: The muscles and their tendons exhibit considerable morphological variations. While the anterior leg compartment may seem uniform, several well-documented variants of the tibialis anterior, extensor hallucis longus (EHL) and extensor digitorum longus (EDL) exist. In contrast, little is known about the fibularis tertius muscle (FT). This literature review aims to compile existing data on the FT and its variations and assess this structure’s clinical significance. Material and Methods: This comprehensive literature review is based on scientific articles obtained from PubMed. All relevant papers were included, and citation tracking was conducted to ensure a thorough examination of the topic. Results: This detailed literature review synthesizes the latest scientific findings regarding the FT, exploring its variable morphology, functional anatomy, evolutionary significance and clinical relevance. A high morphological variability of the FT is described including its origin, insertion and accessory form. Nevertheless, the FT has been described in cadaveric studies between adults and fetuses, while few classification systems have been proposed. Conclusions: The FT is an intriguing structure that has garnered interest from researchers across various fields, including medicine, clinical practice and biological sciences. There are few clinical implications of the muscle such as FT syndrome or tendon tear. Adequate knowledge of its anatomy is of paramount importance for clinicians. Full article

Study Design: Pilot randomized clinical trial. Objective: To examine the effect of electrically evoked muscle hypertrophy on indices of spasticity, as measured by Biodex after spinal cord injury (SCI). Setting: Medical research center. Methods: Thirteen males with chronic SCI were randomized into sixteen weeks of either surface neuromuscular resistance training (NMES-RT) + testosterone treatment (TT) (n = 7) or a TT-only group (n = 6). A Biodex isokinetic dynamometer was used to measure knee extensor and flexor muscle spasticity at the beginning (baseline; BL) and at the end (post-intervention; PI) of 16 weeks. The passive tension of the right knee extensor and flexor muscle groups were evaluated at angles of 5°, 30°, 60°, 90°, 180°, and 270° per second (sec). Dual energy X-ray absorptiometry and magnetic resonance imaging were used to measure leg lean mass and thigh muscle cross-sectional areas (CSAs). Results: Robust muscle hypertrophy was noted in leg lean mass [11%, p = 0.023] as well as whole thigh [17%, p = 0.001] and knee extensor muscle [28%, p = 0.001] CSAs in the NMES-RT+TT compared to the TT-only group. There was no difference in extensor or flexor spasticity between the NMES-RT+TT or TT-only groups at different angular velocities following 16 weeks of intervention. Collapsing the extensor passive torques indicated an (24–28%) increase (p < 0.004) in response to angular velocities at BL and following PI measurements [180 deg/sec (23%; p = 0.03) and 270 deg/sec (32%; p = 0.009)] compared to 5 deg/sec. The extensor slope showed a non-significant (p > 0.05) decrease of 15–28% across all angular velocities. The catch-AB slopes were non-significantly lower in the TT-only group compared to the NMES-RT+TT at higher speeds [90 deg/sec and 270 deg/sec] and attained a trend towards lower passive torque at 180 deg/sec [180 deg/sec: 15.5%, p = 0.05]. Conclusions: Evoking skeletal muscle hypertrophy did not increase spasticity indices at different angular velocities following sixteen weeks of NMES-RT+TT or TT in persons with chronic SCI. Augmenting muscle hypertrophy is likely to attenuate the hyper reflexive slope of the extensor spasticity. The findings may suggest that evoking muscle hypertrophy following NMES-RT does not increase indices of spasticity after SCI. The clinical implications are highly important in managing spasticity after SCI. Full article

Background: Ageing is associated with a progressive decline in muscle strength, particularly in the lower limbs, which compromises functional independence. While both maximum voluntary isometric contraction (MVIC) and one-repetition maximum (1RM) are widely employed to assess muscle strength, the intra-session reliability and predictive capacity of MVIC for estimating 1RM in older women remain insufficiently explored. Objectives: This study aims to evaluate the intra-session reliability of MVIC in knee extensors, analyse its correlation with 1RM, and develop a predictive model for estimating 1RM from MVIC in older women. Methods: Using a randomised split-sample design, 82 women aged 60–69 years performed two MVIC trials and one 1RM test using a leg extension machine. Intra-session reliability was assessed by calculating the intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and the minimal detectable change (MDC). Furthermore, a linear regression model was developed to predict 1RM based on MVIC. Results: MVIC demonstrated excellent intra-session reliability (ICC = 0.96, SEM = 4.3%, MDC = 11.9%), and a strong correlation between MVIC and 1RM was observed (R² = 0.618). Although the predictive equation 1RM = [(0.932 × MVIC) − 3.852] did not yield statistically significant differences between the estimated and actual 1RM values (p = 0.791), it exhibited a prediction error of 13.4%. Conclusions: MVIC is a highly reliable measure in older women and represents a practical tool for estimating 1RM. Nonetheless, its predictive accuracy is limited, highlighting the need for further studies to refine predictive models by incorporating additional variables. Full article

Objectives: Tibial apophysis avulsion fracture is an unusual injury in young pediatric athletes. The mechanism of injury is often related to sports (i.e football and basketball). Fifteen patients who had this kind of fracture underwent surgical Open Reduction and Internal Fixation (ORIF) with two or three cannulated screws and tendon stripping. In this kind of injury and treatment, one of the most important concerns is the recovery of the extensor apparatus strength of the lower limb. Materials and Methods: We followed up the patients for 12 months, performing biomechanical tests and a kinetic analysis to evaluate the activation of the leg muscles such as rectus femoris, vastus medialis, vastus lateralis, and semitendinosus muscle fibers and compared them with the contralateral healthy limb. Results: The results showed that there was an almost complete recovery of muscle strength activation without any statistically significant differences compared to the healthy limb. Conclusions: This surgical treatment appears to be safe and effective in the treatment of tibial apophysis fractures in young athletes, since this type of surgical treatment does not compromise the recovery of the extensor apparatus strength and/or return to sport of the lower limb in case of tibial apophysis fractures in young athletes. Full article

Background and Objectives: The increased prevalence of knee osteoarthritis (OA) and need for total knee arthroplasty (TKA) indicate a growing need for effective prehabilitation. The effect of preoperative home exercise programs (HEPs) on gait in patients with severe knee OA is under-investigated. This study aimed to evaluate the influence of an 8-week preoperative HEP on gait characteristics, leg extensor muscle strength, knee function, and health status in women with severe knee OA scheduled for TKA and to compare them with healthy control data. Material and Methods: Eighteen women with severe knee OA (KOA, aged 61.8 ± 1.6 years) and ten age-matched healthy women (CON) participated in this study. The KOA group performed an HEP with 15 exercises aimed at improving lower limb muscle strength, motion, balance, and coordination. Gait spatiotemporal and kinetic characteristics during the loading response, isometric leg extensor strength, knee active range of motion (AROM), and The Western Ontario and McMaster Universities Arthritis Index (WOMAC) were investigated. Associations between characteristics were analyzed. Results: Improvements in ground reaction force (GRF) during the loading response of gait, leg extensor muscle strength, the knee AROM, and the WOMAC index were found post-HEP. The KOA group demonstrated lower (p < 0.05) spatiotemporal and GRF characteristics than the CON group. Knee extension moment (KEM) was lower pre-HEP (p < 0.05) but did not differ significantly from the CON group post-HEP. Gait characteristics and WOMAC were associated with leg extensor muscle strength and knee AROM and pain in the KOA group. Conclusions: An eight-week preoperative HEP improved GRF and KEM during the loading response of gait, muscle strength, knee function, and self-reported knee OA-related health status in women with severe knee OA. Preoperative HEP before TKA, focusing on leg extensor muscle strength, range of motion, and pain relief, is an effective alternative to supervised exercise therapy in women with severe knee OA. Full article