[Evaluation of the effects of cooling clothes on the adaptation to prolonged exertion in high temperatures by miners].

In order to improve the working conditions of coalminers exposed to high ambient temperature, the authors have studied the effects of wearing an under-vest and a cowl covering the head and shoulders made in sponge-cloth and soaked with cold water (cooling clothes). Eight coalminers volunteered for this study which included three sessions of prolonged intermittent exercise performed in a climatic room with the following ambient temperatures:--experiment A (comfortable environment): td = 28 degrees C; twb = 20 degrees C; bare head and bare torso;--experiment B (hot environment) :td = 38 degrees C; twb = 30 degrees C; bare head and bare torso;--experiment C (hot environment and cooling clothes) : td = 38 degrees C; twb = 30 degrees C; wet undervest and cowl soaked with cold water (16 degrees C) every 15 minutes. Each experiment included 5 periods of exercise each lasting 15 minutes separated by periods of rest lasting 15 minutes; the exercises were performed on a bicycle ergometer or on a treadmill and their intensity corresponded to 50% of the maximal oxygen intake. In the comfortable environment (experiment A), all subjects completed the experiment without undue fatigue; the final heart rate was 81/min and the final rectal temperature was 37.6 degrees C; the weight loss never exceeded 1 Kg. In the hot environment (experiment B), all subjects were exhausted at the end of the study which had to be shortened in 2 cases. The final heart rate was 125/min and the final rectal temperature 38.8 degrees C; the weight loss was above 2 Kg. The use of the "cooling clothes" in the hot environment (experiment C) resulted in significantly (p less than 0.001) lower heart rate (104/min), rectal temperature (38.3 degrees C) and weight loss (1.5 Kg); all subjects completed the experiment, none was exhausted and the "cooling clothes" were appreciated by all subjects. We conclude that the "cooling clothes" tested in the present study significantly reduce the physiological and subjective strain due to intermittent work in a hot environment; this cooling system is simple, of low cost and our results indicate that it is will be very useful in climatic conditions similar to those adopted in the present experimental protocol. Its usefulness in less severe climates has to be established but it might be limited by the subjective reactions of the subjects to the transient but sudden sensation of cold given by the "cooling clothes".