Effect of Jump Direction and External Load on Single-Legged Jump-Landing Biomechanics

External load may increase an individual's risk of non-contact anterior cruciate ligament (ACL) injury during single-legged jump-landing (SLJL). This study evaluated the effects of jump direction and external load on hip and knee joint motion and time to stabilization (TTS) during SLJL. Seventeen active males (n = 8) and females (22.2 ± 3.0 y, 1.75 ± 0.08 m, 73.4 ± 12.0 kg) participated in this randomized, crossover designed study. Single-legged jump-landings performed in two conditions, including without external load (BW) and with a torso-worn weight vest equal to 10% of the participant's body weight (BW+10%), from backward, forward, medial, and lateral SLJL directions. Two-way repeated measures ANOVA did not identify any significant interactions (P > .01, η²: < .001 - .037), but some main effects for condition with small effect sizes were identified (P < .01, η²: .009 - .039). Several main effects for SLJL direction were identified with larger effect sizes (P < .01, η²: .010 - .574). This suggests SLJL direction may challenge different components of SLJL biomechanics, and that recreationally active, college-aged individuals may possess effective compensatory mechanisms that can mitigate the effect of BW+10%.