Kinetic and kinematic characteristics of two-way ballistic exercise across different load conditions: An exploratory impulse–velocity equilibrium analysis

This study aimed to characterize load–dependent force-velocity characteristics during two-way ballistic (TWB) exercise to establish reference for load settings across various intensities. Twenty-four highly trained male athletes (Tier3) performed one-repetition maximum (1-RM) tests at 30%, 40%, 50%, 60%, 70% and 80% 1-RM in random order. Mean propulsive velocity (MPV), peak force (PF), mechanical power output (MPO) and 100-ms impulse during the upward propulsive phase were recorded. Linear regression analyses determined load–velocity, load–impulse and load–power relations. One-way ANOVA assessed intensity effects. Significant effects of load were observed for MPV (η2 = 0.44), MPO (η2 = 0.22) and 100-ms impulse (η2 = 0.81) across intensities (all p < 0.01), while PF showed no significant variation (p = 0.796, η2 = 0.02). MPO peaked at 68.8 ± 13.8% 1-RM. The load–velocity relation showed a moderate negative correlation (R2 = 0.436). The load–impulse relation showed a strong positive correlation (R2 = 0.809). The kinetic efficiency equilibrium (KEE) was identified at 56.5% 1-RM. TWB exercise showed relatively stable power output and limited velocity loss across the tested loading range. The KEE provides a descriptive framework for characterizing the relation between force-time and velocity-related variables within the tested system.