Optimizing stretch-shortening cycle performance: effects of drop height and landing strategy on lower-limb biomechanics in drop jumps.

The stretch-shortening cycle (SSC) enhances performance in jumping, sprinting, and changes of direction. Drop heights and landing strategies affect its efficiency. This study investigates the effects of varying drop heights and landing strategies (hip- vs. knee-dominant) on lower-limb stretch-shortening cycle performance during drop jumps (DJs), which involve a drop followed by an immediate vertical jump. A three-dimensional (3D) motion capture system and force plate collected biomechanical data from 18 college athletes performing DJs with hip- and knee-dominant strategies at 30, 45, and 60 cm heights. A two-factor repeated measures analysis of variance (ANOVA) compared peak impact force, reactive strength index (RSI), leg stiffness (Kleg), joint stiffness (Kjoint), joint angular displacement, change in joint moment, and joint work (positive, negative, net) across heights and strategies. Drop height significantly affected biomechanical variables (p < 0.05). Peak impact force and negative joint work increased from 30 cm to 60 cm, with the highest values at 60 cm. RSI, Kleg, Kjoint, and net joint work peaked at 30 cm. Landing strategy significantly influenced outcomes (p < 0.05). The knee-dominant strategy had higher peak impact force, RSI, Kleg, knee angular displacement, change in knee moment, and ankle work, but lower net knee work, compared to the hip-dominant strategy, which showed higher hip angular displacement and hip work. A significant interaction was observed between drop height and landing strategy (p < 0.05). The knee-dominant strategy had greater RSI, Kleg, and positive ankle work at 30 cm, while the hip-dominant strategy had greater negative ankle work at 60 cm. In DJs, SSC performance was optimised at a 30 cm drop height, with peak efficiency observed in the knee-dominant strategy. At 45 and 60 cm, SSC efficiency declined and knee energy dissipation increased, while the hip-dominant strategy may provide greater joint protection by increasing energy dissipation at the ankle. These findings suggest the knee-dominant strategy is best suited to 30 cm, whereas the hip-dominant strategy may enhance safety at higher drop heights.