Effects of Caffeine and Cold Stress on Exercise Metabolism and Aerobis Work Efficiency

Author: Shen-Yu Hsieh(Department of Physical Education, National Taiwan Normal University)

Abstract：

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.

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