Differences in three-dimensional kinetic determinants of jump height between single- and double-leg countermovement jumps.

Single-leg jumping tasks are directly linked to scoring in various sports; therefore, identifying the biomechanical determinants of higher single-leg jumping performance is crucial for athletic performance. Single-leg jumping can utilize the hip and lumbosacral joints in three dimensions. However, the joint kinetic variables in the frontal and horizontal planes associated with jump height are not fully understood. This study aimed to investigate the differences in joint kinetic factors associated with jump height between single- and double-leg countermovement jumps (CMJs) using waveform statistical analysis. Forty-eight male collegiate athletes performed single- and double-leg CMJs, and lower-limb and lumbosacral joint kinetics were analyzed. The results showed that the extension torque and flexion-extension power of the lower-limb joints were significantly correlated with jump height in single- and double-leg CMJs. Moreover, during the propulsive phase of the single-leg CMJ, greater hip abduction torque, lumbosacral lateral flexion torque, and hip and lumbosacral axial rotation torques were positively correlated with jump height, but not in the double-leg CMJ. The results highlight different mechanisms for achieving higher jump height between single- and double-leg CMJs. The findings suggest that strength training and movement modification targeting the frontal- and horizontal-plane motions may improve single-leg CMJ performance.