Thomas, W. E., Judelson, D. A., Bagley, J. R., Coburn, J. W., Kersey, R. D., & Rubin, D. A. (2010). Effect of caffeine supplementation on cycling performance during cold stress. Presentation 927 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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This study investigated if moderate or high doses of caffeine altered thermoregulatory function, perceptual responses, and cycling performance in cold environments. Competitive male cyclists (N = 8) completed three cycling trials comprised of a 10-minute warm-up (45% of VO2max power), 90-minute endurance ride (60% of VO2max power), and a 20-km simulated time-trial. Ss cycled in a cold environment (5C, 56% RH) with fan-induced wind-chill (18.3 m/s) after consuming placebo, 5 mg/kg caffeine, or 10 mg/kg caffeine in a double-blind randomized fashion. Investigators measured thermoregulatory variables (heart rate, core temperature and skin temperatures), perceptual responses (ratings of perceived exertion and thermal sensation), and performance (20-km simulated time-trial).

Caffeine supplementation significantly increased core temperature during the latter portion of the endurance ride and throughout the time-trial. No consistent significant differences existed for heart rate, skin temperatures, and perceptual variables. Caffeine supplementation also failed to influence 20-km time-trial performance.

Implication. Supplementation of 5 and 10 mg/kg of caffeine increased core temperature during cycling in the cold without affecting heart rate, skin temperature, perceptual sensations, or 20-km time-trial performance. [This is another example of a physiological change not being accompanied by performance change.]

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