Purpose: Pitching machines are widely used for baseball batting practice. However, these machines cannot precisely simulate a live pitcher's pitching motion. To understand if a batter's movement strategy would be altered due to disparate visual information provided by a pitching machine as opposed to a live pitcher, the present study aimed to compare differences in baseball batting movement patterns under the two delivery conditions. Methods: To examine movement variations and different strategies of each high-level athlete rather than obtaining averaged group performance, single-subject analysis was adopted. Four professional baseball players were recruited to bat around 50 pitches under each delivery condition. Vertical ground reaction forces of the participants' batting movements were recorded. Relative timings of key events and values of several kinetic parameters during batting were examined. Results: When batting against the pitching machine, batters initiated forward stepping earlier (relative to ball release), had smaller loading rate at landing the step, and altered the duration from forward bat swing to ball impact. These results might be attributed to lacking visual cues of a live pitcher's whole body kinematics prior to ball release. Without sufficient visual information, greater uncertainty and incomplete weight transfer affected the batter's decision making and movement execution. Conclusion: The batters in this study did adjust their movement strategy in batting against a pitching machine. With dissimilar batting movement patterns under the two delivery conditions, extensive reliance on training with pitching machines is not recommended.
Keywords: Ball delivery method; baseball hitting; coordination; ground reaction forces.