目的：探討攝取咖啡因對休閒運動員心率變異性及反覆高強度衝刺表現之影響。方法：14名具團隊運動訓練背景的大學男性以雙盲、隨機分群和交叉實驗設計的方式，分別進行咖啡因 (caffeine, CAF)與安慰劑(placebo,PLA)處理。受試者攝取每公斤體重6毫克的咖啡因或安慰劑後，採仰臥躺姿勢安靜休息60分鐘並監測心率變異性，之後在腳踏車測功儀上進行24次4秒鐘反覆高強度衝刺運動，間隔休息90秒。結果：CAF的正常心跳間期標準偏差(143.83 ± 42.45 ms)顯著高於 PLA (108.03 ± 31.37 ms, p < .05)。在低頻、高頻、低頻/高頻比值與高頻功率變異係數方面，CAF 與 PLA 之間未達顯著差異， 但CAF的低頻功率變異係數(5.05 ± 1.91%)顯著高於PLA (3.87 ± 1.42%, p < .05)。運動表現結果顯示，CAF的峰值功率比 PLA 高出2.82%(p < .001)，平均功率比PLA高出3.32%(p < .001)。結論：激烈運動前攝取咖啡因導致仰臥姿勢的自律神經活性微幅增加，以及有助於提升反覆性高強度的衝刺運動表現。

Purpose: To investigate the effects of caffeine ingestion on heart rate variability (HRV) and repeated high-intensity sprints performance in recreational athlete. Methods: Fourteen university males with a background in team-sport training and competition participated in this randomized grouping, double-blinded and crossover experimental design. Participants performed the exercise test on a cycling ergometer
after ingestion of either caffeine (CAF, 6 mg • kg-1) or placebo (PLA). The exercise was consisted 24×4-s sprints with 90-s active recovery. The HRV was evaluated in supine position for 60 minutes after the administration of supplementation. Results: Standard deviation of normal-normal RR interval in the CAF trial (143.83 ± 42.45 ms) was significantly higher than in the PLA trial (108.03 ± 31.37 ms, p < .05). No
significant differences were observed in low frequency (LF), high frequency (HF), LF/HF ratio, and coefficients of variation in HF between CAF and PLA trials. However, the coefficient of variation in LF was significantly higher in the CAF trial (5.05 ± 1.91 %) compared with PLA trial (3.87 ± 1.42 %, p < .05). CAF trial resulted in 2.82 % increases in peak power (p < .001) and 3.32 % increases in mean power (p < .001) compared with PLA trial. Conclusion: Ingestion of caffeine prior to vigorous exercise slightly increases autonomic nervous activity, and improves sprint performance during repeated high-intensity test.