The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment
Article first published online: 2 MAR 2005
Acta Physiologica Scandinavica
Volume 183, Issue 3, pages 241–255, March 2005
How to Cite
Saunders, A. G., Dugas, J. P., Tucker, R., Lambert, M. I. and Noakes, T. D. (2005), The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment. Acta Physiologica Scandinavica, 183: 241–255. doi: 10.1111/j.1365-201X.2004.01400.x
- Issue published online: 2 MAR 2005
- Article first published online: 2 MAR 2005
- Received 17 March 2004, accepted 21 October 2004
- air velocity;
- heat storage;
Aim: The purposes of this study were to determine (i) the effects of different facing air velocities on body temperature and heat storage during exercise in hot environmental conditions and (ii) the effects of ingesting fluids at two different rates on thermoregulation during exercise in hot conditions with higher air velocities.
Methods: On five occasions nine subjects cycled for 2 h at 33.0 ± 0.4 °C with a relative humidity of 59 ± 3%. Air velocity was maintained at 0.2 km h−1 (0 WS), 9.9 ± 0.3 km h−1 (10 WS), 33.3 ±2.2 km h−1 (100 WS) and 50.1 ± 3.2 km h−1 (150 WS) while subjects replaced 58.8 ± 6.8% of sweat losses. In the fifth condition, air velocity was maintained at 33.7 ± 2.2 km h−1 and subjects replaced 80.0 ± 6.8% of sweat losses (100.80 WS).
Results: Heat storage, body temperature and rating of perceived exertion were higher in 0 and 10 WS compared with all other conditions. There were no differences in any measured variable between 100 and 150 WS, or between 100 and 100.80 WS. Thus, the evaporative capacity of the environment is increased with higher air velocities, reducing heat storage and body temperature. At higher air velocities, a higher rate of fluid ingestion did not influence heat storage, body temperature or sweat rate.
Conclusion: The finding of previous laboratory studies showing a beneficial effect of high rates of fluid ingestion on thermoregulation during exercise in hot, humid, windstill conditions cannot be extrapolated to out-of-doors exercise in which facing air velocities are seldom lower than the athlete's rate of forward progression.