Ground reaction force and joint force of the blocking leg in javelin throwing correlate with peak throwing shoulder velocity

In javelin throwing, the blocking leg movement is considered crucial for increasing shoulder velocity, yet the relationship between shoulder velocity and blocking leg kinetics remains unclear. In this study, we aimed to quantify blocking leg kinetics and identify factors related to peak shoulder linear velocity. Twenty-eight male javelin throwers performed full run-up throws. Three-dimensional marker coordinates of the whole-body and ground reaction force of the blocking leg were recorded using an optical motion capture system and a force plate. Kinetic variables were calculated via inverse dynamics, and their relationships with peak throwing shoulder velocity were analysed. Ground reaction forces and ankle, knee, and hip joint forces showed significant positive correlations with shoulder velocity. Joint torques and powers showed no significant correlations with shoulder velocity. These results indicate that the linear components of blocking leg kinetics are strongly associated with shoulder velocity, whereas rotational components have a weaker direct effect.