M. A. Seldon, B. F. Hodapp, & D. V. Fischer
College of St. Benedict, St. Joseph, MN

Since the ground is the only external contact for a softball pitcher, ground reaction force (GRF) is theorized to be an important factor in determining softball pitch velocity, yet little research examining this relationship has been published. Purpose: To examine the relationship between the GRF of the stride leg and softball pitch velocity. Methods: Three right hand dominant female Division III intercollegiate softball pitchers (18.3 ±0.6 years; 72.1 ±1.6 kg; 168.0 ±7.9 cm) performed 15 maximal velocity fastball pitches into a net, landing on a force plate with their stride leg, during two separate test sessions (total of 30 pitches per pitcher). Ball velocity was measured to the tenth of one mile per hour using a Stryker radar gun and converted to meters per second. Peak vertical and braking GRFs, sampled at 600 Hz, were normalized to body weight (BW). The slope of the vertical and braking GRFs were calculated by dividing peak GRF by the time from ground contact, defined as the first upward deflection in GRF greater than 5% body weight, to peak force. A Pearson correlation was used to examine the relationship between GRF variables and ball velocity for all 90 pitches. Results: A significant positive correlation was found between ball velocity (23.5 ±0.9 m/sec) and vertical GRF (1.680 ±0.486% BW; r(90) = .854, p < .001), breaking GRF (1.096 ±0.231% BW; r(90) = .696, p < .001), slope of the vertical GRF (32134 ±17697 N/s; r(90) = .221, p = .037), and slope of the braking GRF (12936 ±7680 N/s; r(90) = .378, p < .001) of the stride leg. Conclusion: When a softball is pitched for maximal velocity by Division III softball pitchers using their normal mechanics, there is a positive relationship between GRF variables and ball velocity. Further research is needed to determine whether altering pitching mechanics to accentuate GRF variables will result in greater pitch velocity.

NACSM Professional Sponsor: Donald V. Fischer

This document is currently not available here.