Sex-based differences in landing mechanics vary between the drop vertical jump and stop jump

The purpose of the present study was to compare landing mechanics between the stop jump (SJ) and drop vertical jump (DVJ) and to compare sex-based differences in landing mechanics between tasks. 50 healthy recreational athletes were recruited and each participant completed seven SJs and seven DVJs. Peak knee flexion and abduction angle, knee flexion and ab/adduction range of motion (ROM), peak vertical and posterior ground reaction force (GRF), peak internal knee extension and knee adduction moment were computed for the dominant limb during the first landing of both tasks. A two-way ANOVA was used to determine the effects of and interactions between sex (men vs women) and task (SJ vs DVJ) for each outcome. There was an interaction for peak vertical GRF (p = 0.024), knee flexion ROM (p = 0.027), knee ab/adduction ROM (p = 0.047), and peak knee flexion (p = 0.034) and adduction (p = 0.012) moment. The SJ resulted in smaller vertical GRFs, larger posterior GRFs, and larger peak internal knee adduction moments relative to the DVJ (all p < 0.002). Women landed with larger peak knee abduction angles, larger internal knee adduction moments, and smaller knee extension moments relative to men (p = 0.001-0.026). Overall, as the SJ resulted in larger posterior GRFs and internal knee adduction moments, this task produced movements which resemble most anterior cruciate ligament (ACL) injuries and are risk factors for ACL injuries. As the SJ produced more sex-based differences, it may be better suited than the DVJ for ACL injury risk screening. This study therefore stressed the importance of selecting an appropriate landing task for ACL injury prevention research and clinical return to sport assessment.