Pitching form determines probabilistic structure of errors in pitch location

According to recent motor control studies, it is important to know probabilistic structure of his/her own motor errors to choose an optimal motor plan (i.e., where you aim at) to maximise the expected gain. In this study, we questioned if pitching form determines the probabilistic structure of pitching errors in baseball pitchers. Eighteen collegiate baseball pitchers with various pitching forms including right- and left-handed overarm, sidearm and underarm throwers threw 100 pitches aiming at a target located 90 cm above the ground. Two dimensional distribution of pitch location was fitted by using bivariate normal distribution and 95% confidence ellipse was calculated. In order to quantify the pitching form, the direction of the throwing arm trajectory in frontal plane was calculated. The direction of the long axis was dependent on each participant's pitching form (e.g., right overarm pitchers pitched along a right-up-left-down ellipse and left overarm pitchers pitched along a left-up-right-down ellipse). This was confirmed by circular correlation analysis (P = 0.98). These results suggest that different mechanisms, potentially errors in pitching mechanics and errors in ball release timing, might contribute to errors along the long axis and those along the short axis.