本研究將探討在環境控制下對不同品牌聚氨酯(polyurethane, PU)壘球進行性能比較之分析。其研究方法以實驗方式對一種品牌之PU壘球球芯進行不同環境條件控制，並進行圓周尺寸、重量、恢復係數(coefficient of restitution, COR)與壓縮值等參數值之測試，了解PU壘球球芯特性之趨勢後；再以兩種品牌PU壘球球體為例，進行不同環境條件及球速控制下，測試其恢復係數特性。經由實驗結果顯示，不同環境氣候確實會造成PU壘球球芯圓周尺寸、重量、壓縮值及恢復係數之變化。此外，在不同溫度、溼度控制條件以ASTM標準檢測球速97km/h等速測試下，兩種品牌的COR值差異造成反彈球速差在0.88~1.94km/h間，顯示壘球選手面對不同的比賽單位時，需要更佳的反應來適應不同品牌所造成之影響。最後，在不同球速測試下，兩種品牌的COR值隨著球速愈快而呈現愈低之趨勢，但不同品牌之影響程度並不相同。所以如何於不同氣候比賽下，選擇合適之比賽用PU壘球將是一個重要課題。

This study analyzed the core of a PU softball to better understand the characteristics of circumference, weight, coefficient of resuming (COR) and compressing values. Next, on two brands of PU softballs were experimented to understand the characteristics of COR of the softballs under different environmental conditions and speed testing conditions. The experiment results showed that different environmental conditions changed the parameters of the circumference, weight, COR and compression of the PU softball core. When the same ball speed (97km/h) was set under different temperatures and humidity conditions, the difference in rebound speeds of the two brands was more than 0.88 Km/h. The maximum difference was up to 1.94Km/h. Also, by testing the ball with different speeds, we found that the higher the ball speed, the lower COR. As a result, the differences of characteristics found in each brand of PU softball during different environmental conditions lead to the question of fair play, so the subject arises as to choosing a suitable PU softball in relation to different climates.