Sport, Exercise, and Injury

Gender differences in bilateral and ipsilateral lower limb strength asymmetry among football players

Randy R. Manimtim — 2026-06-02

Background: Lower limb muscle strength asymmetry is a significant factor that can impact playing ability and increase the risk of injury in soccer players. Differences in leg use and the specific movement requirements of a sport can lead to strength imbalances, either on both sides of the body or on the same side. Lower limb muscle strength asymmetry, particularly bilateral and ipsilateral strength asymmetry, is a significant factor influencing performance and increasing injury risk in football players. Differences in limb dominance and sport-specific movement demands can lead to strength imbalances.

Objectives: This study aimed to compare bilateral and ipsilateral lower limb strength asymmetry between male and female football players.

Methods: A cross-sectional study was conducted involving 50 amateur football players (26 males and 24 females; aged 18–21 years). Isokinetic strength testing of knee extensors and flexors was performed at 60°/s. Bilateral asymmetry was calculated based on peak torque differences between limbs, while ipsilateral asymmetry was assessed using the hamstring-to-quadriceps (H/Q) ratio. Statistical analyses included the Mann–Whitney U test and independent t-test (p < 0.05).

Results: Significant sex differences were found in bilateral strength asymmetry for both quadriceps (7.21 ± 4.04% vs 5.04 ± 3.13%, p = 0.02) and hamstrings (9.13 ± 5.15% vs 5.06 ± 4.04%, p = 0.01), with males showing greater asymmetry. Female athletes demonstrated values closer to the recommended asymmetry threshold (≤10–15%). No significant differences were observed in ipsilateral strength asymmetry (H/Q ratio) between groups (p > 0.05).

Conclusions: Bilateral strength asymmetry differs by sex, with male athletes exhibiting higher imbalance, while ipsilateral strength balance is comparable between groups. These findings highlight the importance of monitoring individual strength asymmetry to inform targeted training strategies, reduce injury risk, and optimize performance in football players.

Foot biomechanics and injury risk factors in youth football players: A cross-sectional study

Hamza Sinen — 2026-06-02

Background: Altered plantar pressure distribution and foot alignment have been suggested in previous studies to be associated with ankle instability and overuse injuries; however, evidence in youth populations remains limited.

Objectives: This study aimed to investigate foot biomechanics and potential injury risk factors in youth football players aged 5–15 years.

Methods: This study employed an analytical cross-sectional design involving 30 youth football players recruited from local football academies. Participants were categorized into three age groups: 5–9 years (n = 10), 10–12 years (n = 10), and 13–15 years (n = 10). Data were collected through pedobarographic plantar pressure assessment, hallux valgus angle (HVA) measurement using a goniometer, navicular drop test (NDT), and subtalar angle assessment. Statistical analyses included descriptive statistics, Shapiro–Wilk normality test, Pearson correlation, independent t-test, and one-way ANOVA with effect size (η²). A significance level of p ≤ 0.05 was applied.

Results: The results showed that hindfoot plantar pressure was higher than forefoot pressure in both feet, indicating a posterior loading pattern. Hallux valgus angles were within normal ranges, while subtalar angles demonstrated a tendency toward pronation. Significant differences were observed in left foot HVA and left hindfoot pressure across age groups (p < 0.05), with moderate effect sizes (η² = 0.20–0.21). Correlation analysis revealed moderate to strong positive relationships between subtalar pronation and HVA variables.

Conclusions: Youth football players exhibit biomechanical characteristics, such as increased hindfoot loading and subtalar pronation, that may represent adaptive responses to sport-specific demands and be associated with potential injury risk. However, given the study's cross-sectional design, these findings should be interpreted as descriptive biomechanical patterns rather than as direct predictors of injury. Early biomechanical screening and targeted preventive training may help support optimal athletic development.

Associations and predictive value of isometric strength, isokinetic strength, and anaerobic power for 100-m freestyle performance in young swimmers

Zied Abbes — 2026-06-02

Background: Multiple physical and physiological factors influence sprint swimming performance; however, the relative contributions of isometric strength, isokinetic strength, and anaerobic power to 100-m freestyle performance in young swimmers remain unclear.

Objectives: This study investigated the associations and predictive contributions of physical characteristics, isometric and isokinetic upper-body strength, and anaerobic power to 100-m freestyle swimming performance in young swimmers.

Methods: A cross-sectional study was conducted with 21 male swimmers aged 10–13 years, selected purposively. Eligibility criteria included a minimum of three years of structured swimming training, regular participation in 3–5 training sessions per week, and absence of musculoskeletal injuries. Upper-body strength was assessed using isometric and isokinetic dynamometry (60°/s and 180°/s), while anaerobic power was measured using the 30-s Wingate Anaerobic Test. Swimming performance was evaluated using a 100-m freestyle time trial. Pearson correlation and linear regression analyses were performed after verification of regression assumptions.

Results: Swimming speed was significantly correlated with isometric elbow flexor strength (r = .49, p < .05), isokinetic flexor strength at 60°/s (r = .41, p < .05), and Wingate peak power (r = .37, p < .05). Simple linear regression analysis identified isometric elbow flexor strength as the strongest predictor of swimming performance (B = 0.005, p = .026, R² = .235), followed by isokinetic flexor strength at 60°/s (B = 0.004, p = .038, R² = .210) and Wingate peak power (B = 0.001, p = .031, R² = .198). No significant associations were observed for isokinetic strength at 180°/s.

Conclusions: Upper-body muscular strength, particularly isometric elbow flexor strength, is a significant determinant of 100-m freestyle swimming performance in young swimmers. These findings highlight the importance of maximal force-generating capacity, alongside anaerobic power development, for sprint swimming performance.

Effects of combined exercise and manual therapy on pain and physical function in overweight older adults with knee osteoarthritis: A randomized controlled trial

Seyed Ehsan Hosseini — 2026-06-02

Background: Knee osteoarthritis (KOA) is a prevalent musculoskeletal disorder that leads to pain, reduced mobility, and functional limitations, particularly among overweight older adults. While exercise therapy is widely recommended as a primary non-pharmacological intervention, its effectiveness as a standalone approach may be limited due to increased biomechanical stress in this population.

Objectives: This study aimed to evaluate and compare the effectiveness of exercise therapy alone and a combination of exercise and manual therapy on pain, joint function, range of motion (ROM), and physical performance in overweight older adults with KOA.

Methods: A randomized controlled trial design was employed, involving 40 participants who were randomly allocated (1:1 ratio) using a computer-generated simple randomization sequence. Forty overweight older adults (mean age 58.3 ± 4.9 years; BMI 34.8 ± 3.2 kg/m²) with clinically diagnosed KOA participated in the study. Both groups underwent a 12-session physiotherapy program. Data were collected using the Visual Analog Scale (VAS) for pain, WOMAC for joint function, goniometry for ROM, and the Timed Up and Go (TUG) test for physical performance. Statistical analysis was conducted using JASP, including descriptive statistics, independent-samples t-tests, paired-samples t-tests, repeated-measures ANOVA, and ANCOVA to control for potential confounders.

Results: Both groups demonstrated significant improvements in all outcome measures. Compared with exercise alone, the combined intervention resulted in greater pain reduction (adjusted mean difference = -1.07 points, p < 0.001, η² = 0.52), greater improvement in knee ROM (p < 0.001, η² = 0.61), and better TUG performance (p = 0.001, η² = 0.46). No significant between-group difference was observed for WOMAC scores (p = 0.234, η² = 0.03).

Conclusions: The combination of exercise and manual therapy is more effective than exercise alone in improving pain and physical performance in overweight older adults with KOA. A multimodal physiotherapy approach is recommended to optimize rehabilitation outcomes in this population.