Physiological and subjective responses to thermal transients of exercising subjects dressed in cold-protective clothing.

In cold conditions variations in the physical activity of clothed individuals and rest periods in a moderate temperature may result in a disturbance of heat balance and thermal comfort of the individual, in particular when sweating occurs. The purpose of the study was to examine thermal responses in persons dressed in winter clothing during changes of exercise intensity (high to low) and ambient temperature, and to investigate whether there were any effects on these responses due to fibre material (wool and synthetic). Two types of transient condition were studied, an exercise level transient (E) and a temperature transient (T). Ten healthy male subjects dressed in multi-layer winter clothing ensembles with different levels of total insulation walked on a treadmill at an ambient temperature of -10 degrees C. The garments were manufactured from wool, giving insulations of 2.6 clo, in T only and otherwise of 3.2 clo, or synthetic fibres, giving insulations of 2.4 clo in T only and otherwise of 3.1 clo. In E the subjects exercised at a high intensity for 50 min followed by 60 min walking at low intensity. In T they walked at a moderate speed for 90 min in ambient temperature of -10 degrees C, rested in temperatures of +22 degrees C for 30 min and walked in the cold climatic chamber for another 45 min. The skin temperature, sweating responses and thermal sensations were higher/warmer with increasing insulation during exercise. The wool fibre material resulted in a slightly higher mean skin temperature (about 0.3 degree C) during exercise, but no differences in subjective responses were found. The rest period had only a small influence on the subsequent thermal responses. The interindividual variations in thermal responses were large.