在高溫下從事長時間耐力性的運動不利於運動表現，在常溫下攝取咖啡因從事長時間耐力性的運動，對於運動表現有增補作用。本研究旨在探討攝取咖啡因後，在高溫下從事耐力性的運動，是否像在常溫下對耐力運動有增補作用。受試對象為12名國立台南大學體育系學生。受試對象攝取5mg/kg體重劑量的咖啡因或安慰劑1小時後，在兩種溫度（25℃及35℃）下以70％VO2max的負荷為運動強度騎原地腳踏車直到衰竭為止。測量的情況有四種，採平衡次序方式進行：25℃攝取咖啡因（25C）、25℃攝取安慰劑（25P）、35℃攝取咖啡因（35C）及35℃攝取安慰劑（35P）。實驗結果發現，在運動衰竭時間方面，攝取咖啡因後（25C、35C）比攝取安慰劑（25P、35P）分別顯著的改善了10分41秒（68分38秒 ± 15分26秒 vs. 57分57秒 ± 12分51秒）及10分21秒（53分28秒 ± 14分56秒 vs. 43分01秒 ± 12分26秒）。血漿游離脂肪酸（FFA）濃度在兩種溫度（25℃及35℃）咖啡因與安慰劑攝取前沒有顯著差異，但在攝取咖啡因後1小時及運動後顯著高於安慰劑，攝取咖啡因時，運動衰竭後顯著高於攝取後1小時及攝取前，同時，攝取後1小時顯著高於攝取前。攝取安慰劑時，運動衰竭後顯著高於攝取後1小時及攝取前，但攝取後1小時及攝取前沒有顯著差異。呼吸交換率(RER)在兩種溫度沒有顯著差異；同時在運動前與運動後10、20、30分鐘及運動衰竭時五個時間也都沒有顯著差異。攝取咖啡因與安慰劑之間也都沒有顯著差異。乳酸（La）濃度在兩種溫度沒有顯著差異；在攝取咖啡因與安慰劑前、攝取後1小時及運動衰竭時都沒有顯著差異。運動自覺量表指數（RPE）在運動後10、20及30分鐘，攝取咖啡因顯著低於安慰劑，但在運動衰竭時則沒有顯著差異。本研究結果顯示，攝取咖啡因有助於在35℃溫度長時間耐力運動的運動表現，運動表現的改善關係不在於升高的血漿FFA濃度，而可能是疲勞感的降低所致。

關鍵詞：熱環境、咖啡因、運動表現、耐力性運動

The performance of prolonged endurance exercise can be compromised by conditions of high heat. Caffeine (CAF) has been demonstrated to be a potent ergogenic aid during prolonged endurance exercise in thermoneutral. The purpose of this study was to determine if CAF ingestion could enhance exercise at high temperature. Subjects are 12 male students of National of University of Tainan performed submaximal endurance exercise (SEE) to exhaustion at two temperatures (25℃, 35℃). Subjects received either CAF (5mg/kg) or placebo (PL) capsules 1 h prior to SEE in a double-blind crossover design. The subjects were cycling at approximately 70%VO2max during each of four conditions: (1) 25℃ CAF (25C); (2) 25℃ PL (25P); (3) 35℃ CAF (35C); (4) 35℃ PL (35P). Time to exhaustion were significantly increased (p＜.05) after CAF (25C:68.6 min ± 15.4 and 35C:53.5 min ±14.9) ingestion compared with PL (25P:57.9 min ± 12.8 and 35P:43.1 min ± 12.4). The plasma free fatty acid (FFA) concentration was no significant difference before CAF and PL ingestion, after an hour CAF ingestion and at exhaustion of the plasma FFA concentration were significantly increased in connection with PL ingestion at two temperatures (25℃, 35℃). There was no significant difference in respiratory exchange ratio (RER) between two temperatures. Following the CAF ingestion, when compared with PL, there were no significant differences between CAF and PL at prior to exercise, 10, 20, 30 minutes post exercise and at the time of exhaustion were observed. Lactic acid (La) concentration was not significantly different between two temperatures, before the CAF and the PL ingestion, an hours after the CAF and the PL ingestion or the exhaustion. Rate of perceive exertion (RPE) has significantly difference between CAF and PL at 10, 20, 30 minutes following post exercise, but there was no significant difference at time of the exhaustion. These results demonstrated that CAF enhanced long-term endurance performance in hot environments, while the endurance improvement was independent from the increase in plasma FFA. The study suggests that endurance performance was related to CAF decrease in the perception of fatigue.

Key words：hot environments, caffeine, performance, endurance exercise

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