統計數據分析可以提供客觀的數據，協助教練與球員的主觀判斷，包括球員的各種能力、表現、疲勞與恢復程度等。許多投手在球季當中受傷，或是整季的過度使用而受傷，還有連續幾個球季的高投球量後成績下滑，都可能與投球負荷量有關。本研究目的為探討美國職棒大聯盟與中華職棒合理的使用及保護後援投手的方法，比較後援投手在不同投球局數下的成績表現，以及前一季投球局數對下二季表現的影響，試圖找出合理使用後援投手的方法。本研究探討美國職棒1982-2007年，投球局數超過50、60、70、80、90、100局的後援投手，各項數據後一年和後二年的改變；中華職棒1990-2007年，投球局數超過50、60、70、80、90、100局的後援投手，各項數據後一年和後二年的改變；以及美國職棒前半季投球局數超過25、30、35、40、45、50局的後援投手，後半季各項數據相較於前半季的改變。結果發現美國職棒單季投球局數超過60局的投手，可能有過度使用的現象，投球局數、防禦率、每九局三振數(K/9)、每九局保送數(BB/9)、walks plus hits divided by innings pitched (WHIP)、fielding independent pitching (FIP)、relief earned run average (RERA)、component earned run average (CERA)皆呈現顯著衰退，但少數具有壓制力且能投長局數的後援投手，K/9、BB/9的能力較不受到投球局數增加的影響。中華職棒單季投球局數超過80局的投手，可能有過度使用的現象，後一季、後二季的投球局數皆呈現顯著的減少。美國職棒前半季投球局數25局以上的投手，後半季除了K/9、BB/9無顯著差異外，其餘各項數據皆顯著衰退，顯示半季投球局數超過25局，可能有使用過度的現象。本研究顯示，職棒球隊使用後援投手應該像使用先發投手一樣謹慎，控制投球局數，避免疲勞而造成表現下滑或受傷。

　　The analysis of baseball statistics can provide objective evaluation of performance and help to estimate fatigue and recovery levels. Many pitchers often suffer from injuries during seasons, get injured after an overused season, or perform poorly after several heavy-workloaded seasons. The injuries and performance declines may be related to overuse. The objective of this study is to investigate the appropriate way of using relief pitchers so that they could be protected from possible injury and performance decline in Major League Baseball (MLB) and Chinese Professional Baseball League (CPBL). The study compared the performance of relief pitchers with different innings pitched with their performance in the following 2 seasons. Relief pitchers in MLB with 50, 60, 70, 80, 90, or 100 innings pitched during 1982 and 2007 were analyzed. Relief pitchers in CPBL with 50, 60, 70, 80, 90, or 100 innings pitched during 1990 and 2007 were also analyzed. In addition, the performance of Major League Baseball relief pitchers with 25, 30, 35, 40, 45 or 50 innings pitched before All-Star break was compared with their performance after the break. The results showed that MLB relief pitchers with more than 60 innings pitched in a season may be overused. Their performance was significantly worse in the following 2 years, including innings pitched, earned run average (ERA), strikeouts per 9 innings (K/9), bases on balls per 9 innings (BB/9), walks plus hits divided by innings pitched (WHIP), fielding independent pitching (FIP), relief earned run average (RERA), and component earned run average (CERA). However, certain relief pitchers did show the ability to pitch more innings while maintain their dominance as their K/9 and BB/9 remained stable. In CPBL, the overused consequence occurred when pitching over 80 innings in one season. The number of innings pitched was significantly less in the following 2 years. MLB pitchers with more than 25 innings pitched before the All-Star break showed significant decline in performance in all categories except K/9 and BB/9 after the break. Therefore, overused consequence may occur after pitching more than 25 innings in a half season. This study indicated that professional teams should use relief pitchers with the similar degree of caution as they do with starting pitchers. The number of innings pitched should be clearly monitored to prevent the potential performance decline or injury.