Influence of water temperature on thermal, circulatory and respiratory responses to muscular work

Different muscular exercises have been executed on a bicycle ergometer during immersion in water, the temperature of which varied between 20 and 40 degrees C. During submaximal works, O2 consumption was not modified by the temperature of the water. On the other hand, body temperature (rectal and muscular) are clearly influenced by environment. The temperature of the quadriceps varies from 37.7-38.5 degrees C when the bath temperature rises from 20-40 degrees C during the same work intensity corresponding to 1/3 of the individual maximal work capacity. The rectal temperature was always lower about 0.5 degrees C. Ventilation and heart rate underwent modifications which were significantly accentuated in hot water. Maximal O2 consumption does not reach its highest level in cold water. The low muscular temperature observed in these conditions seems to limit the aerobic metabolism and the working of the muscles. Maximal O2 consumption then rises in parallel with the increase in bath temperature and in body temperatures. In very hot water however (40 degrees C), when rectal temperature rises unduly, the circulatory demand linked to thermolysis becomes excessive, and maximal O2 consumption decreases.