RESUMO
We investigated the sweating response during passive heating (partial submersion up to the umbilical line in 42+/-0.5degrees C water, 30 min) after summer and winter seasonal acclimatization (SA). Testing was performed in July during the summer, 2011 [summer-SA; temp, 25.6+/-1.8degrees C; relative humidity (RH), 82.1+/-8.2%] and in January during the winter, 2012 (winter-SA; temp, -2.7+/-2.9degrees C; RH, 65.0+/-13.1%) in Cheonan (126degrees52'N, 33.38'E), Republic of Korea. All experiments were carried out in an automated climatic chamber (temp, 25.0+/-0.5degrees C: RH, 60.0+/-3.0%). Fifteen healthy men (age, 23.4+/-2.5 years; height, 175.0+/-5.9 cm; weight, 65.3+/-6.1 kg) participated in the study. Local sweat onset time was delayed during winter-SA compared to that after summer-SA (p< 0.001). Local sweat volume, whole body sweat volume, and evaporative loss volume decreased significantly after winter-SA compared to those after summer-SA (p<0.001). Changes in basal metabolic rate increased significantly after winter-SA (p< 0.001), and tympanic temperature and mean body temperature were significantly lower after summer-SA (p<0.05). In conclusion, central sudomotor acitivity becomes sensitive to summer-SA and blunt to winter-SA in Rebubic of Korea. These results suggest that the body adjusts its temperature by economically controlling the sweating rate but does not lower the thermal dissipation rate through a more effective evaporation scheme after summer-SA than that after winter-SA.