棒球投手的投擲動作中，肌肉會進行離心收縮的，一場比賽中反覆的牽扯肌肉，容易造成肌纖維的損傷，進而影響球速下降，甚至可能產生運動傷害。本研究目的為探討棒球投手投球後肌肉損傷的情況，並追蹤其恢復程度，以了解投球後必須休息多久才能讓選手的手臂獲得充分休息。以受過棒球訓練的甲組成棒投手14名為對象，分為先發投手組7名，平均年齡20.0 ± 1.8歲，與救援投手組7名，平均年齡20.0 ± 1.8歲，進行模擬比賽投球。先發投手投6局，救援投手投2局，每局各投15球，其中10顆直球，5顆變化球，運動表現採測量投球量與球速的關係，判定肌肉疲勞程度。在投球前一天早上七點，讓受試者在空腹狀態進行採血，作為基準值，投球後的0、30分鐘、24小時、第二天早晨（day 2）、第三天早晨（day 3）、第四天早晨（day 4）分別採血，分析血漿中肌酸激酶（creatine kinase, CK）、乳酸脫氫酶（lactate dehydrogenase, LDH）、血乳酸（blood lactate acid）、肌紅蛋白（myoglobin）、軟骨低聚物基質蛋白（cartilage oligomeric matrix protein, COMP）之改變。結果顯示，先發投手在投球後的立刻及30分鐘，肌紅蛋白濃度皆顯著高於基準值；在30分鐘時的血乳酸濃度顯著低於救援投手。救援投手的LDH活性在24小時後、CK活性在3天後，皆顯著低於基準值；血乳酸濃度在投球後的立刻與30分鐘都顯著高於基準值。在投球數與球速之間的關係，先發投手在第二局及第五局的直球與變化球球速皆顯著高於第一局。本研究顯示，先發與救援投手在投球後的確會產生肌肉損傷，但休息24小時後就可以充分恢復，且90球內的投球量，先發投手球速並不會因投球量增加而減慢。

　　The repeated eccentric exercise in baseball pitching may result in muscle damage, lower ball speed, or even injury. The purpose of this study was to examine the muscular damage and recovery after baseball pitching. The responses to a bout of baseball pitching were analyzed in 7 starting pitchers (age 20 ± 1.8 yr) and 7 relievers (age 20 ± 1.8 yr). All subjects belonged to a Division I college baseball team. Each subject pitched a simulated game containing 6 (for starters) or 2 (for relievers) innings. Each inning has 15 pitches, including 10 fast balls and 5 breaking balls. Fasting blood samples were withdrawn in the morning on the day before the simulated game as the baseline. Blood samples were also collected immediately, 30 min, and 24 hr after the simulated game, and on the morning of the second, third, and fourth day after the test. Serum levels of creatine kinase, lactate dehydrogenase, lactate, myoglobin, and cartilage oligomeric matrix protein (COMP) were analyzed. In the starting pitchers, myoglobin concentrations were higher in immediately and 30 min after the game compared to the baseline. Blood lactate concentration in 30 min after was lower than that of the relievers in the same time. In the relievers, lactate dehydrogenase activity at 24 hr after, and creatine kinase activity at the third day after the game were significantly lower than the basal levels. Lactate concentrations were higher in immediately and 30 min after the game compared to the baseline. The starters showed higher average speed of fast balls and breaking balls in the second and fifth innings, compared to the first inning. The results of this study suggested that muscular damage occurred after baseball pitching. However, a recovery period of 24 hr would be sufficient to repair the damage. In addition, the starting pitchers can maintain their speed of fast and breaking balls within 90 pitches.