Isokinetic Strength Asymmetries of Trunk Rotation and Knee Joint in Adolescent Female Amateur Boxers: Implications for Injury Prevention

<title>Abstract</title> <p>Objective: To investigate bilateral asymmetries in trunk axial rotation and knee isokinetic strength among adolescent amateur female boxers and provide guidance for sport-specific training and injury prevention. Methods: Sixteen adolescent female amateur boxers (age: 16.8 ± 1.8 years) were tested using the IsoMed 2000 isokinetic dynamometer. Concentric trunk rotation and knee concentric/eccentric strength were assessed at 60°/s, 120°/s, and 180°/s. Paired-samples t-tests and repeated-measures ANOVA were used for statistical analysis. Results: Trunk rotation exhibited significant velocity-dependent asymmetry, with the left (dominant) side producing higher peak torque and total work than the right side at 120°/s and 180°/s (P &lt; 0.01), but not at 60°/s. Eccentric knee strength was significantly greater than concentric strength (P &lt; 0.001). In eccentric mode, the right knee flexors showed superior peak torque and total work compared to the left side (P &lt; 0.01). The hamstring-to-quadriceps (H/Q) ratio was significantly higher on the left side in eccentric mode (P &lt; 0.01), with asymmetry increasing at higher velocities. No significant bilateral differences were observed in concentric mode. Conclusion: Adolescent amateur female boxers demonstrate notable asymmetries favoring the dominant side in trunk rotation and eccentric knee strength. These imbalances, together with relatively low lower-limb strength, may increase the risk of lumbar and knee injuries. Training programs should prioritize balanced bilateral trunk rotational strength, enhanced power production in the non-dominant limb, and optimization of the eccentric H/Q ratio to improve sport-specific performance and reduce injury risk.</p>