Interlimb Asymmetry Data in Athletes With Anterior Cruciate Ligament Reconstruction: A Comparison of Different Equations to Interpret Between-Limb Difference Data

Maestroni, L, Turner, A, Read, P, Bettariga, F, Fenu, G, Rosalia, A, Guastella, M, and Bishop, C. Inter-limb asymmetry data in athletes with anterior cruciate ligament reconstruction: A comparison of different equations to interpret between-limb difference data. J Strength Cond Res 40(2): 158-166, 2026-Between-limb performance and biomechanical differences (i.e., interlimb asymmetries) after anterior cruciate ligament (ACL) reconstruction are monitored and reported during rehabilitation and at the time of return to sport. However, different asymmetry equations can alter the magnitude and consistency of the asymmetry. Fifty-three amateur athletes (16 women; 37 men; 28.5 ± 6.7 years; 177.1 ± 6.5 cm; 75.3 ± 10.8 kg) at a median of 28.1 months post-ACL reconstruction completed a strength and vertical jump assessment including 5 repetition maximum (RM) box squat, rear foot elevated split squats, leg extension and countermovement jump (CMJ), single-leg CMJ, and single-leg drop jump. Large significant differences (ƞ 2 = 0.14-0.44) were found between unilateral equations for each variable assessed, and between bilateral equations (ƞ 2 = 0.17-0.34) for CMJ concentric and eccentric impulse asymmetries. Small to large significant pairwise differences were present between each equation and variable in unilateral tasks ( d = 0.46-2.30). For the CMJ, large significant pairwise differences were also found between most equations for CMJ concentric and eccentric impulse asymmetry ( d = 0.99-3.04). We recommend the use of the Standard Percentage Difference (with direction) formula for unilateral tasks and the Bilateral Asymmetry Index 1 for bilateral tasks.