Effect of high volume stretch-shortening cycle exercise on vertical leg stiffness and jump performance.

The study aims were to investigate the effects of muscle damage induced by high-volume stretch-shortening cycle exercise on countermovement jump (CMJ) performance and vertical leg stiffness during squat and landing phases. Changes in the peak torque of knee extensor muscles, soreness, plasma CK activity, vertical leg stiffness, and CMJ characteristics were measured in recreationally active men after 50, 100, 150 and 200 drop jumps (DJs) and again 24 h later. The isometric voluntary peak torque after 50 DJs decreased by 22 ± 12% (p < 0.01). However, during the squat phase of CMJ eccentric peak power and rate of force development together with the concentric mean force during the push-off phase increased after 50 DJs (all p < 0.05). After 200 DJs, jump height and concentric peak power during push-off were decreased (p < 0.05). At 24 h after exercise, jump height, peak eccentric force, the rate of eccentric force development and the mean concentric force in CMJ and vertical leg stiffness in the squat all remained decreased (p < 0.05), while vertical leg stiffness in the landing phase was increased (p < 0.05). Muscle damaging exercise volume is associated with changes in vertical leg stiffness and CMJ performance.