Invariant multi-joint control strategies are observed during vertical and lateral drop jumps in female athletes despite differences in absolute limb- and joint-level mechanical demands.

Abstract

Drop jump tasks are complex whole-body movements requiring multi-joint control to meet mechanical demands. Unlike drop vertical jumps (DVJs), drop lateral jumps (DLJs) require medial-lateral GRF components that may introduce asymmetry between limbs and increase multi-planar joint demands. The purpose of this study was to compare limb- and joint-level mechanical demands between DVJs and DLJs. Eighteen female athletes performed three drop jump tasks, landing with each foot on separate force plates before jumping vertically or laterally (left or right) with full-body kinematics recorded. Limb-level (resultant GRF and 3D support moment [SM]) and joint-level (angles and net joint moments [NJMs]) demands were compared across conditions. The resultant GRF (p < 0.001, η² = 0.29), SM (p < 0.001, η² = 0.27), and NJMs (p < 0.001, η² = 0.20) were greatest in the DLJ contralateral limb, followed by the DVJ limbs, and then the DLJ ipsilateral limb. Within each condition, hip and knee resultant NJMs were not significantly different (p = 0.099, d = 0.30) and both were greater than the ankle (p < 0.01, d = 0.48-1.24). No joint-by-condition interaction was observed for resultant NJMs (p = 0.76, η² = 0.001). Relative hip (33-34%), knee (36-37%), and ankle (30-31%) contributions to the SM remained consistent, facilitated by alignment (>99%) of the GRF vector with the lower limb plane (LLP). GRF-LLP alignment was maintained via changes in ankle kinematics, and, with the feet relatively fixed on the ground, frontal plane ankle NJMs differed significantly between conditions but were not propagated proximally to the knee or hip. These findings demonstrate that invariant multi-joint control strategies were utilized across conditions, despite differences in absolute limb- and joint-level mechanical demands.