Center-of-mass velocity during the delivery phase in men's javelin throw is not strongly related to deceleration throughout the cross-step phase

Introduction In javelin throwing, the whole-body center-of-mass velocity at the last rear foot contact, marking the onset of delivery phase, is a key determinant of performance. However, velocity changes during the preceding cross-step phase remain poorly understood. This study aimed to quantify the dynamics of center-of-mass velocity throughout the cross-step phase, identify factors influencing these dynamics, and examine their relationship with velocity at the onset of delivery phase. Methods Eighteen right-handed male javelin throwers competing in a national championship were recorded during competition using a digital camera. The final four steps of the cross-step phase were analyzed, and whole-body center-of-mass velocity was calculated. Correlation analyses and repeated-measures ANOVA were performed to assess relationships among variables and to compare within-individual changes. Results Horizontal center-of-mass velocity at the onset of delivery phase was strongly correlated with horizontal velocity at the onset of the cross-step phase (r = 0.890, p < 0.001), whereas weak correlation was observed with the overall velocity decrease during the cross-step phase (r = 0.249, p = 0.319). Additionally, the final cross step exhibited lower velocity than the preceding steps and was strongly correlated with the total velocity decrease throughout the cross-step phase (r = 0.791, p < 0.001). Discussion These findings suggest that interindividual differences in velocity at the onset of delivery phase are more strongly related to initial cross-step velocity than to the magnitude of velocity decrease during cross-step phase. Nevertheless, because velocity decrease was pronounced during the second half of the cross-step, further investigation into mechanical factors underlying deceleration at these steps may provide additional insight into approach velocity regulation.