棒球員需要透過大量的打擊練習以不斷精進這項技能，現今發球機已成為打擊練習有利的輔助器材。然而，發球機畢竟不是真正的投手，其投球方式與打者所習慣的投手投球方式有很大的差異。為了瞭解這樣的差異對於打者的打擊動作策略是否會產生影響，本實驗使用測力板收取三位職業層級的受試者，面對真實投手和發球機兩種打擊情況的地面反作用力資訊，並進行了單一受試者的分析，發現三位受試者面對發球機時都有跨步時機提早、重量轉移速率較慢、以及揮棒啟動至擊中球的時間有顯著差異的現象；而跨步時機的變異性也增加且呈現顯著差異。其餘特徵時序或力學參數的平均或變異性的變化則依受試者各有不同，必須各自解讀。我們認為這些差異主要來自於發球機投球前能提供給打者判斷的訊息不足所產生的不確定性。根據實驗結果我們認為發球機投球的確會對本研究中的受試者在打擊策略上產生變化。因此僅可作為擊球練習的輔助工具而不能取代面對投手的練習。本研究結果也能於提供資訊協助設計更擬真的發球機以改善訓練成效。

Pitching machines are able to offer pitches with both quality and quantity for baseball batting practice. Until now, however, pitching machines still cannot completely simulate a real pitcher’s pitching motion. Whether by rotating a metal arm or squeezing through rubber wheels, none of the pitches generated by pitching machines can provide sufficiently informative cues that batters used to acquire from pitchers before ball release. To understand if a batter would change his strategy of batting movement due to unequal information provided by a pitching machine as opposed to a real pitcher, four professional baseball players in the minor league in Taiwan were recruited. The vertical ground reaction forces of their batting movements were recorded, and all three subjects were analyzed as a single subject. We examined several time instants of events and also some kinetic parameters. It turned out that every subject stepped earlier, shifted weight more slowly with a significant difference during “swing to impact” in facing a pitching machine. The variability of stepping was also raised. However, the other parameters had different characteristics among subjects and needed to be interpreted individually. These results may be attributed to lack of visual clues which could be found in a real pitcher’s whole body kinematics, and resulted in an uncertainty for the batter. Therefore, it was concluded that our participants did change their batting movement strategy in the batting practice with a pitching machine. It has to be noted that it is premature to generalize this conclusion to larger population due to small sample size used in this study.

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