Acute Effect of the Bounce Squat on Ground Reaction Force at the Turning Point and Barbell Kinematics.

Abstract

Abstract: Achermann, BB, Drewek, A, and Lorenzetti, SR. Acute effect of the bounce squat on ground reaction force at the turning point and barbell kinematics. J Strength Cond Res XX(X): 000-000, 2025-The free-weight back squat is a key exercise for developing lower-body strength, with variations that influence muscle activation and performance. The bounce squat, a variation involving a controlled bounce, increases the eccentric velocity at the squat's bottom. In this study, we aimed to investigate the effects of the bounce squat, descent velocity, and load on barbell kinematics and ground reaction force (GRF) during back squats. In addition, we explored the prediction of GRF from barbell kinematics. Overall, 29 participants completed 2 sessions, including bounce and no-bounce squats. Session 1 was focused on the load (70 and 80% 1RM), whereas session 2 examined the descent velocity (fast vs. slow). Data were analyzed using linear mixed-effects models (p = 0.05). Bounce squats increased the GRF significantly by 19 and 22% (sessions 1 and 2, respectively). Furthermore, it increased the peak velocity in the early concentric phase (Vpeak1) and reduced it in the late concentric phase (Vpeak2). Higher loads significantly reduced the mean concentric velocity (Vmean), minimum velocity, Vpeak1, and Vpeak2, and minimally enhanced the GRF. Faster descent enhanced Vmean and Vpeak2 without affecting the GRF or Vpeak1. These findings emphasize balancing performance with musculoskeletal stress and underscore the importance of accurate technical execution of back squats. Supporting factors such as descent velocity and load should be tailored to preserve the optimal technique. Predicting GRF from barbell kinematics highlights its potential for monitoring squat performance.