Ground Reaction Forces and Peak Throwing Shoulder Forces in Softball High School Pitchers

To optimize pitching performance, pitchers must generate substantial ground reaction forces to aid pitch velocity while minimizing the forces experienced in their throwing shoulder. Extremely high shoulder forces are generally thought to be injurious for softball pitchers. Therefore, this study aimed to identify the relationship between ground reaction forces during the propulsion phase of the pitch and peak shoulder forces during the pitch. Thirty-two high school softball pitchers (1.70±0.06 m, 76.09±17.50 kg, and 15±1 y) pitched fastballs for strikes. Kinematic and kinetic data from the three fastest pitches were averaged for analysis. The relationships between ground reaction forces during pitch propulsion and peak shoulder kinetics during the propulsion and acceleration phases were examined via multiple regressions and correlations. A vertical ground reaction force was significantly associated with a peak resultant shoulder force (t=-3.176 and p=0.003). The rate of ground reaction force development was correlated with the peak shoulder distraction force (r=-0.367 and p=0.033) and the resultant force during propulsion (r=-0.439 and p=0.009). These observations underscore the potential significance of lower body contributions and kinetic chain sequencing in reducing shoulder forces during the early stages of the pitch, which may have implications for injury risk as ground reaction forces during pitch propulsion may decline with fatigue.