Effects of Drop-height and Surface Instability on Jump Performance and Knee Kinematics

The purpose of this study was to examine the combined effects of drop-height and surface condition on drop jump (DJ) performance and knee joint kinematics. DJ performance, sagittal and frontal plane knee joint kinematics were measured in jump experienced young male and female adults during DJs on stable, unstable and highly unstable surfaces using different drop-heights (20, 40, 60 cm). Findings revealed impaired DJ performance (Δ5–16%; p 40 cm) together with highly unstable surfaces should be used cautiously during plyometrics because this may increase the risk of injury due to higher knee valgus stress.