Anthony W. Fava1, Jessica L. Talmage2, Gretchen D. Oliver, FACSM1. 1Auburn University, Auburn, AL. 2Northern State University, Aberdeen, SD.

BACKGROUND: Baseball pitchers utilize their lower extremities as force generators to supply energy up the kinetic chain to maximally deliver the ball. A pitcher’s ability to absorb and produce force up the kinetic chain are influenced by neuromuscular and mechanical properties. In order to achieve certain performance outcomes such as throwing different pitch types, a pitcher’s stride leg stiffness may be altered due to anticipatory factors as well as their ability to transform energy upon landing. The purpose of this study was to examine stride leg stiffness between different pitch types. METHODS: Fifteen baseball pitchers (age: 15.7 ± 1.2 y; height: 178.2 ± 5.2 cm; weight: 72.5 ± 8.6 kg) completed fastball (FB), curveball (CV), and change up (CH) pitches for a strike at regulation distance (18.4 m) off a mound. Kinematic data were collected at 240 Hz using an electromagnetic tracking system. A force plate with a sampling rate at 1200 Hz was used to collect ground reaction force (GRF). Vertical GRF (VGRF) was measured during the arm-cocking phase: stride foot contact to maximal shoulder external rotation. Stride limb length was measured as resting limb length between the greater trochanter and the lateral malleolus. Limb length displacement of the pitcher was determined as the difference between resting stride limb length and the instantaneous leg length in the Y-direction. Leg stiffness was calculated using the ratio of VGRF and leg displacement normalized to body weight. The max leg stiffness during the arm-cocking phase for each pitch type was used for analysis. A within-subjects repeated measures analysis of variance (ANOVA) with leg stiffness as the dependent variable was used to assess whether leg stiffness differs by pitch type. RESULTS: The ANOVA determined that mean leg stiffness did not significantly differ between pitch types, (F 2, 28 = 2.677, p = .086). Mean leg stiffness values for each pitch type include: FB: 19.6 ± 3.6 Nm/kg; CV: 17.4 ± 3.9 Nm/kg; and CH: 18.7 ± 4.6 Nm/kg. Additionally, the effect size was small, partial ƞ2 = .161. CONCLUSIONS: Results indicate that in the current population stride leg stiffness did not differ between pitch types. The current findings on leg stiffness in high school pitchers warrants further investigation with larger and diverse samples to examine how leg stiffness relates to performance and injury risk in baseball pitchers.

This document is currently not available here.