Relationships between the ground reaction force during initial sprint acceleration and the vertical force–velocity profile

Abstract

Aim This study examined the relationships between the ground reaction force (GRF) during sprint acceleration and lower-limb mechanical capabilities derived from the vertical force–velocity (F-V) profile. Materials and methods Thirty-one male collegiate baseball players performed 15-m sprint accelerations. The mean horizontal and resultant GRFs and leg extension velocities in the propulsive phase were calculated for the first, fifth, and ninth steps during sprint acceleration. From the F-V profile estimated by squat jumps under 5–6 loading conditions (0–100kg), the theoretical maximum force (F0), velocity (V0), power (Pmax), and dynamic lower-limb strength corresponding to the leg extension velocities at each step during sprint acceleration (F1st, F5th, and F9th) were obtained. Correlations between GRFs during sprint acceleration and F-V profile-derived variables were examined. Results F0 moderately to largely correlated with the horizontal GRFs for all steps (r=.359 to .543; P=.002 to .047). Pmax moderately correlated with the horizontal GRFs for the fifth and ninth steps (r=.357 and .448; P=.049 and .011, respectively) and resultant GRF for the ninth step (r=.380; P=.035). No significant correlations existed between dynamic lower-limb strengths and GRFs, except for F1st and resultant GRF for the first step (r=.364; P=.045). Conclusions Greater lower-limb maximal strength and power contribute to a greater horizontal GRF generation in the entire and latter early phases of sprint acceleration, respectively. Thus, strength training tailored to neuromuscular demands for each step may be effective for enhancing sprint acceleration performance.