INFLUENCE OF SKIN TEMPERATURE ON SWEATING AND AEROBIC PERFORMANCE DURING SEVERE WORK

Two male subjects were measured over a range of work intensities at dry-bulb temperatures (T(db)) = 21°C (relative humidity, rh <50%) and at approximately 65 and 85% VO2(max) for 1 h at T(db) at 5, 10, 15, 21, and 25°C with high convective airflow (2.5-5 m/s). The results showed that mean skin temperature [T(sk)] was related to T(db) and unaffected by rh over the range studied. T(sk) was dependent on the relative work load and was 2.5°C lower at 85% than 65% VO2(max) in the cooler environments. During submaximal work the relative sweat rate [M(sw) expressed as %M(sw,max)] was a linear function of rectal temperature [T(re)] and T(sk) for each subject and thus %M(sw,max) could be predicted from these two variables with a standard deviation of ±12%. For a given T(sk), T(re) appeared to rise to meet the requirement of heat loss by stimulating set %M(sw) response. However, during severe work [85% VO2(max)] this mechanism appeared to become saturated, T(re) (except for a very narrow prescriptive range) was dependent on T(db). These results suggest that under moderate environmental conditions the maximal aerobic and evaporative (cooling) power outputs of an individual are closely matched and only during extremely hard work does thermoregulation become passive and effectively physical (rather than physiological) in nature.