Pitching biomechanics as a pitcher approaches muscular fatigue during a simulated baseball game

The effects of approaching muscular fatigue on pitching biomechanics are currently unknown. As a pitcher fatigues, pitching mechanics may change, leading to a decrease in performance and an increased risk of injury.

As a pitcher approaches muscular fatigue, select pitching biomechanical variables will be significantly different than they were before muscular fatigue.

Controlled laboratory study.

Ten collegiate baseball pitchers threw 15 pitches per inning for 7 to 9 innings off an indoor throwing mound during a simulated baseball game. A pitching session ended when each pitcher felt he could no longer continue owing to a subjective perception of muscular fatigue. A 6-camera 3D automatic digitizing system collected 200-Hz video data. Twenty kinematic and 11 kinetic variables were calculated throughout 4 phases of the pitch. A repeated-measure analysis of variance (P < .01) was used to compare biomechanical variables between innings.

Compared with the initial 2 innings, as a pitcher approached muscular fatigue during the final 2 innings he was able to pitch, there was a significant decrease in ball velocity, and the trunk was significantly closer to a vertical position. There were no other significant differences in kinematics or kinetics variables.

The relatively few differences observed imply that pitching biomechanics remained remarkably similar between collegiate starting pitchers who threw between 105 and 135 pitches for 7 to 9 innings and approached muscular fatigue.

This study did not support the idea that there is an increase in shoulder and elbow forces and torques as muscular fatigue is approached. It is possible that if a pitcher remained in a fatigued state for a longer period of time, additional changes in pitching mechanics may occur and the risk of injury may increase.