Anthony W. Fava1, Jessica Downs-Talmage2, Nicole Bordelon1, Gretchen D. Oliver, FACSM1. 1Auburn University, Auburn, AL. 2Northern State University, Aberdeen, SD.

BACKGROUND: Softball pitchers who compete in double header (DH) games are subjected to increased daily pitch volumes with little rest time. PURPOSE: To determine the effects of increased daily pitch volume on stride leg kinetics in softball pitchers. METHODS: Twenty-six (14±1yr,1.6±.18m,74.8±15.8kg) high school softball pitchers active on a team roster participated. Pitchers performed a simulated game (SG) of 25 randomly assigned pitches for four innings. Following the SG, a 30-minute break was provided. After the break, participants pitched one inning of a simulated DH game. Kinematic data were collected using an electromagnetic tracking system, and kinetics were determined in biomechanical software using inverse dynamics. Net stride hip and knee forces and torques were analyzed across the first (T1) and last innings (T2) of the SG and DH inning (T3). Joint forces were normalized to bodyweight (BW), and net joint torques were normalized to BW·height (BWH). The average max kinetics from stride foot contact to ball release from 3 fastballs were analyzed. Two within-subjects multivariate ANOVA tests were used to determine if stride hip and knee kinetics significantly differed across time points. A within-subjects ANOVA was used to test changes in pitch speed. RESULTS: No significant changes were observed in net stride hip forces or torques between time points as daily pitch volume increased (λ=.97,F4,22=.14 p=.96). No significant changes in net knee forces or torques were found between time points as daily pitch volume increased (λ=.96,F4,22=.21, p=.93). Significant decreases in pitch speed (F2,50=49.38, p<.001) occurred between T1 and T2 (p<.001) and T1 and T3 (p<.001) but not T2 and T3 (p=.695). Net hip joint forces were T1=265.2±97.3; T2= 276.6±118.9; T3=275.2±103.2 %BW. Net hip joint torques were T1=46.9±23.5; T2=47.3±18.9; T3=47.6±18.5 %BWH. Net knee joint forces were T1=216.2±86.5; T2=208.4±79.2; T3=205.2±74.4 %BW. Net knee joint torques were T1=23.9±9.6; T2=23.7±8.4; T3=23.6±7.8 %BWH. Pitch speeds were T1=52.6±4.4; T2=50.9±4.7; T3=51.2±4.0mph. CONCLUSION: Performance decreased while stride hip and knee joint kinetics were sustained across time. Therefore, demands on the body remain similar across bouts of pitching, which could present a risk for injury. Conditioning to support kinetics and promote energy transfer to the pitching arm should be considered.

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