Neuromuscular Adaptation to Varying Drop Jump Heights: A Muscle Synergy Approach in Elite Handball Players

Rapid single-leg landings and rebounds are central to high-performance handball, yet little is known about neuromuscular coordination adaptations to changing mechanical demands under such conditions. This study examined how different landing heights would modulate lower limb muscle synergy patterns in elite male handball players performing single-leg drop jumps. Twenty professional athletes executed rebound jumps from five standardized heights (0.15-0.75 m). Kinematic data, ground reaction forces, and surface electromyography (sEMG) from seven lower limb muscles were collected and synchronized. Muscle synergies were extracted using non-negative matrix factorization (NMF), while the temporal characteristics of activation patterns were analyzed with SPM1d. Across landing heights, synergy dimensionality remained stable while both muscle weightings and phase-specific activation (pre-activation, buffering, propulsion) were systematically modulated. These height-dependent adjustments were consistent with redistribution within existing motor modules rather than isolated muscle-specific changes. Practically, programming unilateral plyometrics at ~0.60 m may elicit the most pronounced, yet controlled, adaptation of braking and push-off strategies relevant to impact-force management.