No Effect of Nutritional Adenosine Receptor Antagonists on Exercise Performance in the Heat
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA THERMAL AND MOUNTAIN MEDICINE DIVISION
Pagination or Media Count:
Nutritional adenosine receptor antagonists can enhance endurance exercise performance in temperate environments, but their efficacy during heat stress is not well understood. This double-blinded, placebo-controlled study compared the effects of an acute dose of caffeine or quercetin on endurance exercise performance during compensable heat stress 40 C, 20-30 rh. On each of three occasions, 10 healthy men each performed 30-min of cycle ergometry at 50 Vo2peak followed by a 15-min performance time trial after receiving either placebo Group P, caffeine Group C 9 mgkg, or quercetin Group Q 2,000 mg. Serial blood samples, physiological heart rate, rectal, and mean skin body temperatures, perceptual ratings of perceived exertion, pain, thermal comfort, motivation, and exercise performance measures total work and pacing strategy were made. Supplementation with caffeine and quercetin increased preexercise blood concentrations of caffeine 55.62 - 4.77 micrometers and quercetin 4.76 - 2.56 micrometers above their in vitro inhibition constants for adenosine receptors. No treatment effects were observed for any physiological or perceptual measures, with the exception of elevated rectal body temperatures 0.20 0.30 C P 0.05 for Group C vs. Groups Q and P. Supplementation did not affect total work performed Groups P 153.5 - 28.3, C 157.3 - 28.9, and Q 151.1 - 31.6 kJ P 0.05 or the self-selected pacing strategy employed. These findings indicate that the nutritional adenosine receptor antagonists caffeine and quercetin do not enhance endurance exercise performance during compensable heat stress.
- Anatomy and Physiology
- Stress Physiology