Two-dimensional trial-by-trial error correction for accurate baseball pitching

Throwing an object accurately at a target position at high-speed repeatedly is a specific human motor skill. The arrival position of the thrown ball is approximately determined by its physical state at release. In high-speed baseball pitching, reducing the variability in the ball's elevation/azimuth angle of the velocity at release (release angle) is particularly necessary to reduce the variability in the vertical/horizontal arrival position. However, as there is always variability in human movements, which increases as the speed increases, decreasing the variability is an issue. This study focused on one strategy, trial-by-trial error correction, which is to correct movements in the subsequent trials facing an undesirable outcome. Fourteen skilled baseball pitchers' intertrial changes in the elevation/azimuth release angle of 30 balls were analyzed together by transition probability analysis in addition to a separate analysis using the autocorrelation function. The results showed a difference in error correction depending on the state and direction, and Friedman's test for the transition probability from state to state showed a significant difference in the rank means [chi-squared = 25.79, df = 15, p = 0.04]. In addition, this suggests that the pitchers with large variability in the release angle made fewer corrections in the horizontal direction. These findings indicate that trial-by-trial error correction can be a strategy to decrease variability however, complicated factors are involved in error correction.