Search Results (150)

Background: Youth soccer players are exposed to repeated unilateral loading during a period of rapid growth and neuromuscular maturation. These demands may contribute to postural deviations and inter-limb functional asymmetries that can influence movement control and mechanical efficiency. This study protocol aims to establish a standardized multimodal framework for assessing postural alignment, postural control, lower limb mechanical output, ankle dorsiflexion strength, support-limb neuromuscular activation, and contextual training and recovery variables in licensed youth soccer players aged 13 to 17 years. Methods: This prospective observational study will include 75 male youth soccer players recruited from S.C. Fotbal Club Ripensia Timișoara S.A. The primary outcome is the inter-limb asymmetry index derived from unilateral countermovement jump performance. Secondary outcomes include postural alignment, balance, bilateral jump performance, ankle dorsiflexion strength, and support limb electromyographic activity during the instep kick. Participants will complete a clinical evaluation questionnaire, including demographic, training, and recovery variables. Assessments will be conducted using the GaitON system, Kinvent K-Delta force platforms, K-Myo surface electromyography, and K-Pull dynamometry, before and after a regular training session. Biological maturation will be estimated using the Mirwald maturity offset method. Expected Results: The protocol will allow characterization of inter-limb asymmetries across postural, balance, jump, and electromyographic parameters. Conclusions: This protocol aims to provide a practical and standardized model for functional screening in youth soccer players. Full article

(1) Background: Asymmetry in strength, movement, and neuromuscular control is common in youth sports, yet its role in anterior cruciate ligament (ACL) injury risk in pediatric athletes remains underexamined. (2) Methods: This narrative review synthesized studies that examined lower-limb asymmetry, biomechanics, ACL injury or reconstruction (ACLR), and rehabilitation in participants younger than 18 years, supplemented by key mechanistic and methodological work. (3) Results: Evidence indicates that asymmetry is multifactorial and sometimes functional, arising from limb dominance, sport-specific loading, growth-related morphological change, and neuromuscular variability. However, asymmetry becomes concerning when it coincides with high-risk landing or cutting mechanics, growth-related coordination deficits, or incomplete recovery after ACL reconstruction. Persistent strength and loading asymmetries are linked to secondary ACL injury and early structural joint changes, whereas neuromuscular training and technique-modification programs can improve symmetry and reduce high-risk mechanics. Major gaps include the absence of pediatric-specific asymmetry norms, limited longitudinal and sex-specific data, and heterogeneous measurement approaches. (4) Conclusions: Clarifying when asymmetry is adaptive versus maladaptive, and integrating this knowledge into screening, rehabilitation, and return-to-sport decision-making, will be essential for optimizing performance and promoting lifelong knee health in pediatric athletes. Full article

Objective: The primary aim of this study was to compare eccentric knee flexion isokinetic performance at two commonly used angular velocities (60°·s⁻¹ and 180°·s⁻¹) between dominant and non-dominant limbs in healthy professional soccer players through the analysis of peak torque, mean peak torque, angle of peak torque, total work, and rate-of-torque-development-related variables. The secondary aim was to describe concentric knee extension and knee flexion strength variables assessed at 60°·s⁻¹. Methods: Forty male professional soccer players performed concentric knee flexion–extension testing at 60°·s⁻¹ and eccentric knee flexion testing at 60°·s⁻¹ and 180°·s⁻¹ using an isokinetic dynamometer. Peak torque (PT), mean peak torque (MPT), angle of peak torque (APT), total work (TW), and hamstrings: quadriceps ratios (H:Q ratios) were analyzed for dominant and non-dominant limbs. Inter-limb differences, repetition effects, and reliability indices were calculated. Results: No significant inter-limb differences were observed for most variables (trivial–small effect sizes), except for higher eccentric TW at 180°·s⁻¹ in the dominant limb (p = 0.009). Eccentric PT and MPT decreased at higher velocities in both dominant (p = 0.002 and p < 0.001, respectively) and non-dominant (p = 0.008 and p < 0.001, respectively) limbs, while APT shifted toward more flexed knee angles (p < 0.001). Reliability was good to excellent (ICC = 0.81–0.87), with low measurement error. Conclusion: Eccentric knee flexion assessment at 60°·s⁻¹ and 180°·s⁻¹ angular velocities provided different results in PT, MPT, and APT for the same group of players, supporting the use of more than one eccentric test for obtaining information about these variables in elite soccer. Full article

Abnormal gait associated with neuromuscular and musculoskeletal disorders represents a growing clinical burden, particularly in aging populations. This study presents a modular, low-cost Smart Rehabilitation Walker (SRW) that integrates multimodal sensing and real-time haptic feedback to enable simultaneous gait monitoring and corrective intervention in both clinical and home environments. The system combines force-sensing resistors for bilateral load symmetry assessment, inertial measurement units for fall detection, and surface electromyography (sEMG) for neuromuscular activity monitoring within a closed-loop assistive feedback architecture. A 15-day pilot study involving ten individuals with rheumatoid arthritis and clinically observed neurological gait abnormalities demonstrated measurable improvements in gait biomechanics. The Force Symmetry Index (FSI), calculated using the Robinson symmetry metric, decreased from an average of 0.9691 to 0.2019, corresponding to a 79.26% average reduction in inter-limb load asymmetry. Concurrently, sEMG measurements showed a substantial increase in neuromuscular activation (ΔEMG = 4.28), with statistical analysis confirming a significant improvement across participants (paired t-test: t(9) = 13.58, p < 0.001). To model rehabilitation trajectories, a nonlinear predictive framework based on Gaussian Process Regression achieved high predictive accuracy (R² ≈ 0.9, with a mean RMSE of 0.0385), while providing uncertainty-aware trend estimation. Validation using an independent amyotrophic lateral sclerosis gait dataset further demonstrated the transferability of the analytical pipeline. These results highlight the potential of sensor-enabled assistive walkers as scalable platforms for quantitative gait rehabilitation, adaptive feedback, and long-term mobility monitoring. Full article

This study investigated interlimb asymmetries in lower limb performance using both vertical and horizontal jump tests in elite young basketball players. Specifically, it aimed to determine whether (1) unilateral jump performance and (2) the magnitude of interlimb asymmetry differed across maturity groups, whether (3) limb dominance influences performance, and whether (4) asymmetry direction is consistent across tests. One hundred elite male basketball players (U13 to U19) were categorised into three maturational stages: Pre-PHV (n = 19), Circa-PHV (n = 29), and Post-PHV (n = 52). Each athlete performed the following unilateral tests with both the dominant and non-dominant leg: single-leg hop, triple hop for distance, 6 m timed hop, single-leg countermovement jump (SL-CMJ), and single-leg drop jump (SL-DJ) from a 30 cm box. The Bilateral Strength Asymmetry (BSA) index was computed for each test. All tests showed significant differences between Pre-PHV and Circa-PHV groups (p < 0.001), whereas only the 6 m timed hop differed between Circa-PHV and Post-PHV (p < 0.01). BSA did not differ significantly across maturation stages in any test, except for the single-leg hop. Agreement in asymmetry direction between test pairs was slight to fair (kappa ≤ 0.29). BSA values remained largely stable across maturational stages, suggesting that interlimb asymmetries are established before PHV, likely during childhood. Limb dominance did not affect jump performance, and asymmetry direction varied between tests, confirming they are not interchangeable. Full article

Background: Upper limb functional performance depends on the interaction of strength, mobility, and neuromuscular control, while inter-limb asymmetries may increase injury risk. However, comprehensive analyses integrating these factors remain limited. This study aimed to evaluate sex differences and identify functional phenotypes in young adults using a multidimensional assessment approach. Methods: Forty-six healthy young adults (23 women, 23 men) underwent a comprehensive battery of upper limb assessments, including anthropometric measurements, maximal handgrip strength, isometric elbow flexion and extension torque, postural stability via the Fall Risk Index (FRI), and functional reach using the Upper Quarter Y-Balance Test (YBT-UQ). Inter-limb symmetry was calculated using the Limb Symmetry Index (LSI). K-means clustering was applied to standardized variables to identify latent functional phenotypes. Results: Men demonstrated significantly greater body mass, height, limb length, and absolute strength (p < 0.01), while functional performance (YBT-UQ composite scores) and inter-limb symmetry were similar between sexes. Strength asymmetry was most prevalent for elbow flexion and handgrip strength (up to 89%), whereas stability asymmetry was less frequent (≈54%). Three functional clusters were identified: Cluster 1—high strength and moderate stability, Cluster 2—lower anthropometry and strength, Cluster 3—high strength but reduced stability and increased asymmetry. Despite phenotypic differences, composite functional performance was comparable across clusters. Conclusions: Upper limb function reflects the interaction of morphological and neuromuscular factors rather than strength alone. Observed asymmetries should be interpreted within a functional context, as moderate asymmetries may represent normal variation in motor control, while larger asymmetries may indicate potential functional imbalance; however, due to the cross-sectional design of this study, no causal inferences regarding injury risk can be made. Functional phenotyping provides a framework for individualized training, screening, and rehabilitation strategies. Full article

Inter-limb asymmetries are common in soccer players and are frequently monitored in high-performance settings; however, their expression across different flywheel-based strength exercises, movement phases, and over time remains unclear. This study aimed to (i) compare inter-limb power asymmetry magnitudes across multiple unilateral flywheel exercises and between concentric (CON) and eccentric (ECC) phases, and (ii) describe changes in these asymmetries over an 8-week period of routine soccer training, stratified by baseline asymmetry magnitude. The present study was designed as an observational and descriptive study. Twenty-one professional male soccer players completed two testing sessions separated by eight weeks. Players performed six unilateral flywheel exercises targeting hip- and knee-dominant quadriceps (Qhip, Qknee), hip- and knee-dominant hamstrings (Hhip, Hknee), adductors (ADD), and abductors (ABD). For each exercise and limb, the repetition with the highest CON mean power and its consecutive ECC phase were selected for analysis. Inter-limb asymmetry (%) was calculated for mean and peak power in both phases. Across exercises, ECC asymmetries were generally greater than CON asymmetries, with the largest values observed for Qknee peak power (CON: 12.86 ± 11.04%; ECC: 27.60 ± 13.65%) and Hknee peak power (CON: 10.45 ± 11.26%; ECC: 24.01 ± 20.46%). Exercise-specific patterns were evident, with generally weak associations between asymmetries across tasks. Over time, players classified with higher baseline asymmetry (≥10%) presented lower values at follow-up in several outcomes (particularly ECC-related measures), whereas players with lower baseline asymmetry (<10%) showed small increases or remained stable; These between-group patterns should be interpreted cautiously, as they may be more strongly influenced by regression to the mean and measurement variability than by underlying physiological changes. Overall, inter-limb power asymmetries assessed with flywheel technology were phase- and exercise-specific in this professional soccer sample. These descriptive findings may help contextualize phase-specific and multi-exercise asymmetry monitoring in professional soccer settings. Full article

Objective: The effects of fatigue on swimming propulsion are unclear. This study examined upper-limb propulsive force and bilateral coordination during constant-speed front crawl performed until exhaustion. Methods: Twelve competitive swimmers completed a visually paced front-crawl trial performed at a constant speed (95% of maximal speed) until volitional exhaustion. Upper-limb propulsion (pressure-derived) was quantified using wearable differential-pressure mini-paddles synchronized with high-speed video. Propulsive force and impulse were analyzed at ten standardized time points (10–100% of test duration), distinguishing the early (entry–catch–pull) phase and the push phase of the stroke cycle. Results: Total overall propulsive impulse (time-integral of propulsive force) and mean propulsive force decreased significantly as early as 30–40% of test duration, with the largest reductions occurring during the push phase. Interestingly, push-phase impulse declined earlier in the non-dominant left arm (from 20% of test duration) compared to the dominant right arm (from 40%), whereas force generated during the early phase did not change. Peak propulsive force decreased at later stages, while intra-cycle timing indices (peak timing and force centroid) and inter-limb asymmetry remained unchanged. Stroke frequency increased from mid-test onward and was strongly negatively associated with stroke efficiency (r = −0.79). Stroke efficiency correlated positively with push-phase impulse and peak force. Conclusions: During constant-speed front crawl performed to exhaustion, propulsion progressively declines, primarily through reduced force and impulse during the push phase rather than changes in the early (entry–catch–pull) phase or temporal and asymmetry-related variables. Increased stroke frequency initially compensates for declining propulsion but ultimately fails to maintain the imposed swimming velocity. Full article

Background/Objectives: The paretic wrist after stroke may exhibit median nerve conduction abnormalities, but factors underlying hemiplegic–contralateral asymmetry remain uncertain. We compared electrodiagnostic and ultrasonographic wrist measures between sides and assessed predictors of side-to-side differences in distal motor latency (ΔDML) and distal sensory latency (ΔDSL). Methods: We retrospectively analyzed 85 patients with stroke. Distal motor latency (DML), distal sensory latency (DSL), wrist-to-forearm ratio (WFR), and median nerve inlet cross-sectional area (CSA) were measured bilaterally. Paired t-tests evaluated hemiplegic–contralateral differences, and Wilcoxon signed-rank tests were performed as sensitivity analyses. Multivariable linear regression with robust (HC3) standard errors modeled ΔDML as the primary outcome and ΔDSL as the secondary outcome, with wrist flexor spasticity (Modified Ashworth Scale, MAS) specified a priori as the primary explanatory variable; extended models additionally included ΔWFR. Sensitivity analyses re-specified MAS as an ordered category, and complementary linear mixed-effects models using raw bilateral latency values were fitted to assess the robustness of Δ-based modeling. Results: The hemiplegic side showed higher DML (5.51 ± 0.79 vs. 4.81 ± 0.42 ms; mean difference 0.694; p < 0.001), DSL (4.51 ± 0.88 vs. 3.66 ± 0.45 ms; mean difference 0.852; p < 0.001), WFR (1.21 ± 0.30 vs. 1.07 ± 0.16; p = 0.008), and CSA (11.16 ± 3.67 vs. 9.69 ± 2.04 mm²; p = 0.032). MAS was associated with ΔDML (β = 0.336; p < 0.001) and ΔDSL (β = 0.238; p = 0.015). ΔWFR remained significant for ΔDML (β = 1.314; p < 0.001) and ΔDSL (β = 1.371; p = 0.001), improving adjusted R² from 0.251 to 0.370 for ΔDML and from 0.142 to 0.253 for ΔDSL. Findings remained directionally consistent when MAS was modeled as an ordered category. Complementary mixed-effects models using raw bilateral latency values showed significant hemiplegic-side-by-MAS interactions for both DML (β = 0.425; 95% CI 0.275 to 0.575; p < 0.001) and DSL (β = 0.366; 95% CI 0.195 to 0.537; p < 0.001). Conclusions: In chronic stroke hemiplegia, median nerve latencies and wrist morphology may differ between sides. Wrist flexor spasticity and side-to-side increases in WFR may be independently associated with greater latency asymmetry. These interlimb latency differences should be interpreted as physiological markers of side-to-side median nerve involvement at the wrist rather than as stand-alone diagnostic criteria for carpal tunnel syndrome. Full article

The aim of this study was to examine temporal changes in eccentric hamstring strength, impulse-based mechanical outputs, and interlimb asymmetry in professional football players performing a football-specific eccentric hamstring training program. Forty male football players (18–25 years) from two teams competing in the Turkish Second Professional Football League participated in this longitudinal cohort study. Eccentric hamstring performance was assessed at three time points (pre-, mid-, and post-season) using the NordBord Hamstring Testing System. Mixed-design repeated-measures ANOVA revealed significant main effects of time and significant time × Team interactions for left and right maximal impulse values (p < 0.05). In contrast, maximal eccentric force variables showed no significant time effects, although significant time × Team interactions were observed for both limbs (p < 0.05). Interlimb maximal force asymmetry and mean asymmetry demonstrated significant time effects, while Team effects and interaction terms were not significant. Overall, these findings indicate that temporal changes in eccentric hamstring performance in professional football players may be more clearly reflected in force–time–dependent metrics, particularly impulse, rather than peak force outputs. Accordingly, impulse-based measures may provide additional insight into eccentric hamstring performance changes in professional football players. Full article

Human locomotion relies on a proximal–distal organization of joint mechanical work that adapts to task constraints, such as those imposed by inclined walking. In individuals with transtibial amputation, loss of the biological ankle disrupts this organization, leading to proximal alterations and inter-limb asymmetries. Active mechatronic prosthetic feet have been developed within a biomechanical biomimicry framework to restore distal positive mechanical work. This exploratory study quantified the effects of an active mechatronic prosthetic foot on joint mechanical work during inclined walking. Four individuals with transtibial amputation performed instrumented treadmill walking at −3°, 0°, and +3° using their habitual passive foot and a powered foot. Positive and negative mechanical work at the ankle, knee, and hip were computed using inverse dynamics and compared with a normative reference database (n = 20). The powered foot induced modest, task-dependent modifications, mainly at the ankle and knee. In downhill walking, it promoted a more symmetrical redistribution of negative mechanical work, particularly at the knee, suggesting a partial reduction in contralateral overload. In uphill walking, distal assistance increased prosthetic-side positive work, reflecting slope-dependent reallocation rather than normalization. Although a multivariate deviation score indicated reduced deviation under the powered condition, full convergence toward the asymptomatic organization was not achieved. Full article

Background: Alpine skiing imposes high biomechanical demands on the lower limbs, which are further amplified in individuals with transfemoral amputation due to prosthetic constraints. This study aimed to quantify three-dimensional knee flexion asymmetries during alpine skiing turns in transfemoral amputee skiers compared with non-disabled controls. Methods: Five unilateral transfemoral amputee skiers (intervention group) and five non-disabled ski instructors (control group) performed six left and six right turns on a skiing simulator under laboratory conditions. Knee flexion angles at the apex of each turn were analyzed using three-dimensional motion capture. Intra-individual differences between the prosthetic and intact limbs were assessed using paired comparisons, and inter-individual differences between groups were evaluated using independent statistical tests (p < 0.05), performed in IBM SPSS Statistics. Results: Intra-individual analysis revealed significant knee flexion asymmetries (p < 0.05) in almost all amputee participants at the apex of both left (mean difference = 7.74°, 95% CI: 3.38–12.09) and right turns (mean difference = 4.36°, 95% CI: 2.66–6.06). In the control group, asymmetries were smaller and reached significance only for the inside leg in both turns (mean difference = 4.02°, 95% CI: 2.51–5.54). Inter-individual comparisons demonstrated significant differences between the groups for both turning directions. During left turns (prosthetic limb on the inside), the largest difference was observed for the inside leg (26.9°, p < 0.001), while the smallest difference occurred for the outside leg (12.1°, p = 0.013). During right turns (prosthetic limb on the outside), the largest difference was found for the outside leg (19.0°, p < 0.001), with a smaller but still significant difference for the inside leg (14.0°, p < 0.001). Conclusions: Transfemoral amputee skiers exhibit a turning strategy that is qualitatively comparable to that of non-disabled skiers; however, it is characterized by a reduced knee flexion range of motion. These limitations appear to be primarily influenced by prosthesis mechanics and user-specific skill levels rather than by a fundamentally different movement strategy. Full article

Objectives: This study examined whether 8 weeks of unilateral flywheel resistance training (FRT) enhances eccentric neuromuscular characteristics and change-of-direction (COD) performance in male soccer players, and whether these adaptations transfer to sport-specific dribbling and match-play demands. Methods: Twenty-four male soccer players were randomized to a unilateral flywheel training group (EXT, n = 12) or a traditional resistance training control group (CON, n = 12). Both groups completed unilateral lower-limb strength training twice weekly for 8 weeks. Eccentric knee extensor and flexor peak torque (60°·s⁻¹), eccentric-to-concentric (E:C) ratio, and inter-limb asymmetry were assessed using isokinetic testing. Performance measures included a 10 m sprint, modified 505, COD deficit, a dribbling-based COD test (AFL), and GPS-derived high-intensity acceleration and deceleration metrics during matches. Results: Compared with CON, the EXT group showed greater increases in knee extensor (+0.54 Nm·kg⁻¹) and flexor (+0.46 Nm·kg⁻¹) eccentric peak torque, a higher E:C ratio, and reduced inter-limb asymmetry (all p < 0.05). While 10 m sprint performance remained unchanged, EXT improved modified 505 performance and reduced COD deficits (up to −0.06 s). In addition, AFL completion time decreased and match-play high-intensity acceleration and deceleration events increased in EXT compared with CON (p < 0.05). Conclusions: Unilateral FRT effectively enhances eccentric braking-related capacity and COD efficiency, with clear transfer to soccer-specific technical performance and high-intensity match-play demands. Full article

Background: In soccer, the repeated execution of unilateral actions may lead to uneven limb development, promoting the occurrence of asymmetries. However, there is no consensus on the impact of these asymmetries on sports performance or the influence of playing position on their magnitude. Methods: A cross-sectional study was conducted with 33 male federated soccer players (age: 18.42 ± 4.24 years; body mass: 70.23 ± 8.74 kg; height: 1.76 ± 0.07 m; body mass index: 22.6 ± 2.7 kg/m²). Hamstring strength asymmetry between the dominant and non-dominant limbs was assessed using functional electromechanical dynamometer (FEMD) at eccentric velocities of 0.4, 0.8, and 1.2 m/s. Physical performance was evaluated through a 30 m sprint and countermovement jump (CMJ). Differences according to playing position were also analyzed. Results: Significant between-limb differences were found in strength, power, and impulse, with effect sizes increasing as testing velocity rose. No significant differences in asymmetry levels were observed across playing positions, and no correlations were found between hamstring asymmetry and physical performance outcomes. Conclusions: Although functional lower-limb asymmetries were identified in soccer players, these asymmetries did not directly influence performance nor vary across playing positions. The findings suggest that certain asymmetries may represent normal functional adaptations in soccer rather than pathological structural imbalances. Full article

Background and Objectives: This study compared functional performance, gait performance, and dynamic balance between Coronal Plane Alignment of the Knee (CPAK) Type I and Type II patients undergoing unilateral total knee arthroplasty (TKA). Materials and Methods: We included 162 consecutive patients scheduled for unilateral TKA between January 2022 and August 2025. Patients were classified according to CPAK type; 42 were Type I and 33 were Type II. Preoperative assessments included demographic data, Korean Knee Score, and WOMAC. Functional performance was evaluated using the Timed Up and Go (TUG) test and the 4 m walk test. Isokinetic knee extensor and flexor strength (60°/s), hip abductor strength, and bilateral thigh circumferences measured 5 cm and 15 cm proximal to the patella were assessed. Dynamic balance asymmetry was evaluated using the POSTUROMED device. Inter-limb differences were calculated by comparing the operated and non-operated limbs. Results: No significant between-group differences were observed in clinical scores, knee extensor, or flexor strength deficits, hip abductor strength deficits, or thigh circumference differences. However, CPAK Type II patients demonstrated significantly better functional performance, with faster TUG (p = 0.014) and 4 m walk test times (p = 0.022). Dynamic balance outcomes were also significantly better in the Type II group (p = 0.042). Conclusions: Despite similar patient-reported clinical scores and muscle strength, patients with the CPAK Type II phenotype exhibited superior gait performance and dynamic balance compared with those with Type I following unilateral TKA. Full article