Lower limb asymmetry in mechanical muscle function: A comparison between ski racers with and without ACL reconstruction

Due to a high incidence of anterior cruciate ligament ( ACL ) re‐injury in alpine ski racers, this study aims to assess functional asymmetry in the countermovement jump ( CMJ ), squat jump ( SJ ), and leg muscle mass in elite ski racers with and without anterior cruciate ligament reconstruction ( ACL ‐ R ). Elite alpine skiers with ACL ‐ R ( n  = 9; 26.2 ± 11.8 months post‐op) and uninjured skiers ( n  = 9) participated in neuromuscular screening. Vertical ground reaction force during the CMJ and SJ was assessed using dual force plate methodology to obtain phase‐specific bilateral asymmetry indices ( AIs ) for kinetic impulse ( CMJ and SJ phase‐specific kinetic impulse AI ). Dual x‐ray absorptiometry scanning was used to assess asymmetry in lower body muscle mass. Compared with controls, ACL ‐ R skiers had increased AI in muscle mass ( P  < 0.001), kinetic impulse AI in the CMJ concentric phase ( P  < 0.05), and the final phase of the SJ ( P  < 0.05). Positive associations were observed between muscle mass and AI in the CMJ concentric phase ( r  = 0.57, P  < 0.01) as well as in the late SJ phase ( r  = 0.66, P  < 0.01). Future research is required to assess the role of the CMJ and SJ phase‐specific kinetic impulse AI as a part of a multifaceted approach for improving outcome following ACL ‐ R in elite ski racers.