Rates of ground reaction force development are associated with running speed during sprint acceleration

This study aimed to investigate the relationship between overground sprint performance and rates of force development (RFDs) in ground reaction forces (GRF) during the entire acceleration phase. Thirty-one male sprinters performed 60-m sprints during which the GRF from the start to the 50-m mark were measured. The vertical, braking and propulsive RFDs at each step were calculated as the average rate of change in GRF. Average values for each four steps during the acceleration phase were calculated to examine relationships between running speed or average horizontal external power (AHEP) and RFD values. The RFD values ranged from 859.8 +/- 191.1 to 1682.0 +/- 258.2 N/s/kg for vertical force, -502.6 +/- 215.7 to -1033.8 +/- 196.2 N/s/kg for braking force, and 97.2 +/- 11.7 to 185.4 +/- 32.3 N/s/kg for propulsive force. There were associations of running speed with vertical RFD at the 21(st)-24(th) step section (r=0.385) and with propulsive RFD at the 1(st)-4(th) step section and from the 13(th)-16(th) to 21(st)-24(th) step sections (r=0.386-0.559). Moreover, AHEP was correlated with vertical RFD from the 13(th)-16(th) to 21(st)-24(th) step sections (r=0.442-0.523), with braking RFD at the 17(th)-20(th) and 21(st)-24(th) step sections (r=-0.423 and -0.448), and with propulsive RFD at every step section (r=0.374-0.856). In conclusion, greater propulsive RFD throughout the acceleration phase, along with higher braking and vertical RFD during the later acceleration section, may indicate better sprint performance.