The dynamic control ratio masks bilateral asymmetries–A gender-specific analysis of 264 healthy and ACL-injured athletes

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OBJECTIVES: Anterior cruciate ligament (ACL) ruptures are severe injuries which impair athletes’ careers. Isokinetic strength measurements are frequently applied to prevent knee injuries, support athlete’s rehabilitation and take return-to-sport decisions. However, test designs and parameters differ causing misleading conclusions. This cross-sectional study evaluated the effects of gender (male vs. female), group (healthy vs. ACL-injured) and limb (dominant/healthy vs. non-dominant/ACL-injured) on thigh muscle balance of athletes. METHODS: Matched pairs of 138 female and 126 male athletes (50% ACL-injured) performed unilateral isokinetic tests of concentric knee extensor (Qcon) and eccentric knee flexor (Hecc) movements (30°/s, 150°/s). Thigh muscle balance was analysed between legs (bilateral asymmetry) and between agonist and antagonist (DCR=dynamic control ratio, DCRe=DCR at the equilibrium point). RESULTS: Averagely 12.8 months after reconstruction (77% hamstring graft, 58% dominant side involved), male and female ACL-injured athletes demonstrated comparable bilateral asymmetries (7-20%) in peak (PMQcon, PMHecc) and DCRe moments (0.018≤ηp²≤0.215). These deficits were independent of the time after surgery. ACL-injured athletes’ affected (24-28%) and unaffected (12-24%) leg was significantly weaker compared to healthy athletes (0.061≤ηp²≤0.362) for knee flexors and extensors. Generally, healthy and ACL-injured female athletes were 17-27% weaker than their male counterparts. DCR induced ~50% false negative attributions (<10% bilateral asymmetry) compared to PMQon. CONCLUSIONS: Even more than 1 year after surgery, male and female ACL-injured athletes suffered from considerable comparable strength deficits in both legs. Peak and DCRe moments served to detect bilateral asymmetries, whereas DCR did not. This knowledge might contribute to improve the design and interpretation of isokinetic tests.
ZeitschriftScandinavian journal of medicine & science in sports
PublikationsstatusVeröffentlicht - 2021

ID: 5538232

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