Biomechanical mechanisms of lower limb adaptations to drop-jump height in sprinters under fixed load conditions

The stretch-shortening cycle (SSC) is critical to explosive movements; recent methods favor fixed relative loading over bodyweight-only depth jumps to better replicate competitive demands. Twenty-four male sprinters performed drop jump tests from five heights (0.20–0.60 m), each with a fixed load equivalent to 10% of their body weight. Three-dimensional kinematic and kinetic data were acquired via a Vicon motion analysis system coupled with force platforms. Key variables included ground reaction force, joint moments and powers, average power output, and reactive strength indices. Repeated-measures ANOVA assessed the effects of height. Drop height significantly affected peak ground reaction force ( p = 0.002), hip and ankle moments and powers ( p < 0.05), average power output ( p = 0.004), RSI ( p = 0.002), and RSR ( p = 0.003). Most variables peaked or leveled off at ≥0.40 m, with 0.40 m offering the best peak force and contact time optimal trade-off. A 0.40 m drop height with a 10% bodyweight load optimally enhances lower limb explosive strength and reactive power in sprinters. This load–height combination facilitates neuromuscular adaptation while potentially minimizing injury risk. Therefore, this paper is recommended as a targeted prescription for sprint-specific SSC training protocols designed to improve SSC efficiency and explosive performance under controlled loading conditions.