咖啡因和冷刺激對運動代謝和有氧工作效率的影響

EFFECTS OF CAFFEINE AND COLD STRESS ON ECERCISE METABOLISM AND AEROBIS WORK EFFICIENCY

本驗研究咖啡因和冷刺激在人體浸滯水中時對運動恣謝和有氧工作效率（AWE, 每消耗1公升的氧所能做的功）的影響。受試者是十名健康的男子(29.4+3.4歲, 77.1+6.7公斤)浸滯在水中做腳踏車運動55分鐘。其運動強度為每公斤體重每分1.5瓦特，平均分鐘117+11瓦特。測驗情況有四種：28度C非 藥劑(Placebo)(28P)，28度C咖啡因（每公斤體重5毫克）(28CF)，18度C非藥劑(18P)和18度C咖啡因(18CF)。非藥劑或 咖啡因均在運動前90分鐘服用。實驗結果發現耗氧量因咖啡因和冷刺激而顯著的上昇。耗氧量最大者為18C（2.56升╱分）而最小者為28P（2.32升 ╱分）。AWE則因咖啡因和冷刺激的影響而顯著的降低。血液中游離脂肪酸(FFA)因咖啡因而昇高，但因冷刺激而被抑制。FFA以 28CF(1.24mml/L)最高，以18P(0.62mml/L)最低。血液中的乳酸也顯著的受咖啡因和冷刺激的影響而提昇。乳酸最高是在 18CF(5.6mml/L)而最低是在28P(3.8mml/L)。結論：運動時咖啡和冷刺激能推加式的使耗氧量提昇，而同時降低AWE。咖啡因和冷刺激促進的是無氧代謝而不是有氧代謝。

Caffeine (Cf) or cold alone affects lipid metabolism. The combined effects of Cf and cold stress on exerciese metabolism and aerobic work efficiency (AWE)， defined as work output (Watts) divided by liters of 02 consumed (W/L 02)， was studied during head-out impersion. Ten males (29.4+3.4 yrs， 77.1 +6.7 kg) exercised on a cycle ergometer at 1.5 W/kg (117+11 W) for 55 min. The 4 test conditions were: 28 or 18 C water with placebo (P) or Cf (5 mg/kg). Cf or P was ingested 90 min before exercise Qxygen consumption (VO2) at 117W was elevated significantly by Cf and by cold. The highest VO2 occurred at 18Cf (2.56 1/min) with the lowest at 28P (2.23 1/min). AWE was decreased by Cf and cold and varied inversely with VO2. Plasma free fatty acids (FFA) were significantly elevated by Cf nd may be inhibited by cold. The highest FFA occurred at 28Cf (1.24 mmol/L) and the lowest at 18P (0.62 mmol/L). Blood lactate was significantly raised by Cf and by cold. The highest lactate was at 18Cf (5.6 mmol/L) and lowest at 28P (3.8 mmol/L). CONCLUSIONS: Caffeine and cold immersion elevate VO2 additively and thus decrease o.AWE during moderate eccercise. Both Cf and cold seem to promote anaerobic， not aerobic metabolism.