自行車選手攝取7種不同劑量咖啡因對運動表現的影響：整合分析

Effects of seven different doses of caffeine on exercise performance in cyclists: Meta-analysis

前言：咖啡因（caffeine）作為運動增補劑，能夠幫助運動員顯著提高運動表現是學界公認的觀點，但是對人體生理的反應機制目前尚不清楚。因此，攝取7種不同劑量的咖啡因對運動員的表現是否有顯著差異，目前學界依舊存在爭論。方法：本研究採用整合分析的方法，透過文獻檢索探討自行車選手攝取1-2、3、5、6、9、10-15mg/kg, BM（body mass）及固定200-400mg, BM等不同劑量的咖啡因對運動員表現進行分類比較，同時針對不同劑量咖啡因與運動表現的相關性進行研究。結果：與安慰劑相比，攝取不同劑量的咖啡因對自行車選手的TT、MPO和TTE提升率分別為-12.12%、5.04%和20.51%。但在TT和MPO表現中只有6mg/kg, BM對自行車選手有顯著提升（p< .05）比對照組用時縮短-2.66%，MPO平均功率輸出增加6.32%。另外在TTE表現中，固定劑量200-400mg, BM和9mg/kg, BM兩個類別對選手有顯著提高（p < .05）比對照組延遲時間提高了22.1%和22.5%。相關分析顯示，在TT表現中，攝取3、5、6mg/kg, BM三種劑量對自行車選手表現都有提升，但是6mg/kg, BM劑量的（R2 = 0.82, p < .05）是最可靠的劑量；MPO表現中，攝取3mg/kg, BM和固定200-400mg, BM是負相關；然而，6mg/kg, BM是最佳的劑量（R2 = 0.63，p < .05）。在TTE表現中，攝取9、10-15mg/kg, BM劑量有顯著提高，同時9mg/kg, BM對TTE表現較穩定（R2 = 0.87, p < .05）；另外固定劑量200-400mg, BM對TTE為負相關。結論：在攝取不同劑量咖啡因中6mg/kg, BM對運動員在TT和MPO表現為最佳劑量，而在TTE表現中，以攝取9mg/kg, BM為最佳劑量，研究結果能夠為運動員和教練在增補攝取咖啡因時，能選擇有效劑量提供科學的依據。

Introduction: It is well recognized that caffeine, as a sports supplement, can help athletes to significantly improve their performance, but the mechanism of its physiological response is still unclear. Therefore, it is still debatable whether the intake of seven different doses of caffeine can make a significant difference in athletes' performance. Methods: In this study, meta-analysis was conducted to investigate the effects of different doses of caffeine, such as 1-2, 3, 5, 6, 9, 10-15 mg/kg, BM (body mass) and fixed 200-400mg, BM, on the performance of cyclists, and the correlation between the different doses of caffeine and the athletic performance was also investigated. The correlation between different doses of caffeine and athletic performance was also investigated. Results: Compared with placebo, different doses of caffeine improved the TT, MPO and TTE of cyclists by -12.12%, 5.04 % and 20.51%, respectively. However, in TT and MPO performance only 6 mg/kg, BM showed significant enhancement (p < .05) in cyclists (-2.66 %) compared to the control group in terms of time reduction and 6.32 % increase in mean power output in MPO. In addition, in TTE performance, the fixed-dose 200-400mg, BM and 9mg/kg, BM categories showed a significant improvement (p < .05) over the control group in terms of delay time by 22.1% and 22.5%. Correlation analysis showed that in TT performance, all three doses of 3, 5 and 6 mg/kg, BM improved the performance of cyclists, but the 6 mg/kg, BM dose (R2 = 0.82, p < .05) was the most reliable dose; in MPO performance, the intake of 3 mg/kg, BM and fixation of 200-400mg, BM were negatively related; however, 6 mg/kg, BM was the optimal dose; and in MPO performance, the intake of 3 mg/kg, BM and fixation of 200-400mg, BM were negatively related; however, the intake of 3 mg/kg, BM and fixation of 200-400mg, BM were the best dose. In MPO performance, 3mg/kg, BM intake and 200-400mg, BM fixation were negatively correlated; however, 6mg/kg, BM was the optimal dose (R2 = 0.63, p < .05). In TTE performance, the dose of BM was significantly higher at 9, 10-15 mg/kg, while 9 mg/kg of BM was more stable in TTE performance (R2 = 0.87, p < .05); the fixed dose of 200-400mg of BM was negatively correlated with TTE. Conclusion: Among the different doses of caffeine, 6 mg/kg of BM was the optimal dose for TT and MPO performance, while 9 mg/kg of BM was the optimal dose for TTE performance. The results of this study provide a scientific basis for athletes and coaches to choose a safe and effective dose of caffeine when supplementing their caffeine intake.