Effects of Mixed Training on Biomechanical Risk Proxies for ACL Injury in Trained Youth Basketball Athletes

Mixed training may serve as a tool to mitigate injury risk by reducing lower-limb asymmetries, enhancing neuromuscular control, and optimizing landing biomechanics. The purpose of this study was to investigate the effects of mixed training on unilateral lower-limb stiffness (LLS) and the landing error scoring system (LESS) as biomechanical risk proxies associated with anterior cruciate ligament (ACL) injuries. Thirty-two trained youth male basketball athletes were randomly assigned to a French contrast, a contrast, or a complex training protocol in a six-week mesocycle with a training frequency of twice per week. All groups performed pre‐ and post‐training intervention measurements of unilateral drop jump stiffness and the bilateral drop jump LESS. Two-way ANOVAs revealed significant interaction effects between the round and the protocol for non-dominant LLS (p = 0.03) and the LESS (p = 0.003). Athletes experienced significant and pronounced improvements in non-dominant LLS and the LESS following complex (LLS: p = 0.0008, d = 1.30; LESS: p = 0.005, d = 1.41) and contrast (LLS: p = 0.017, d = 1.10; LESS: p = 0.007, d = 1.35), but not French contrast training strategies. Linear regression showed significance (p = 0.009), with changes in non-dominant LLS accounting for 21% of the variance in LESS changes. Our findings demonstrate the effectiveness of both complex and contrast training as an indirect ACL injury risk minimization tool via improvements in non-dominant LLS and the LESS. Such improvements may be attributed to post-intervention neuromuscular adaptations, including greater higher-threshold motor unit recruitment, rate coding, and synchronization.