In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0± 0.7 years; 80.5±2.0 kg; 180±2 cm, mean ± SE) exercised for 60 min in a hot, dry environment (40±0°C and 45±0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1°C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored.

To evaluate the effects of heat acclimation on sweat rate redistribution and thermodynamic parameters, 9 tropical native volunteers were submitted to 11 days of exercise-heat exposures (40Ϯ0°C and 45.1Ϯ0.2% relative humidity). Sudomotor function was evaluated by measuring total and local (forehead, chest, arm, forearm, and thigh) sweat rates, local sweat sodium concentration, and mean skin and rectal temperatures. We also calculated heat production (H), heat storage (S), heat exchange by radiation (R) and by convection (C), evaporated sweat (E sw ), sweating efficiency (h sw ), skin wettedness (w sk ), and the ratio between the heat storage and the sum of heat production and heat gains by radiation and convection (S/(HϩRϩC)). The heat acclimation increased the whole-body sweat rate and reduced the mean skin temperature. There were changes in the local sweat rate patterns: on the arm, forearm, and thigh it increased significantly from day 1 to day 11 (all pϽ0.05) and the sweat rates from the forehead and the chest showed a small nonsignificant increase (pϭ0.34 and 0.17, respectively). The relative increase of local sweat rates on day 11 was not different among the sites; however, when comparing the limbs (arm, forearm, and thigh) with the trunk (forehead and chest), there was a significant higher increase in the limbs (32Ϯ5%) in comparison to the trunk (11Ϯ2%, pϭ0.001). After the heat acclimation period we observed higher w sk and E sw and reduced S/(HϩRϩC), meaning greater thermoregulatory efficiency. The increase in the limb sweat rate, but not the increase in the trunk sweat rate, correlated with the increased w sk , E sw , and reduced S/(HϩRϩC) (pϽ0.05 to all). Altogether, it can be concluded that heat acclimation increased the limbs' sweat rates in tropical natives and that this increase led to increased loss of heat through evaporation of sweat and this higher sweat evaporation was related to higher thermoregulatory efficiency.

A partir da hipótese evolutiva de que a cabeça humana precisa ser resfriada de forma especial, o objetivo do presente estudo foi verificar se a sudorese seria maior na testa do que nas demais regiões do corpo durante o exercício progressivo até a fadiga (EPF). Em 17 voluntários (23 ± 2 anos, 76,93 ± 7,74 kg, 179 ± 7 cm e 1,9 ± 0,1 m²) foram medidos a taxa de sudorese local (TSlocal), o número de glândulas de suor ativas (GSA) e taxa de suor por GSA (TSlocal.GSA-1) em oito regiões do corpo (testa, costas, peito, braço, antebraço, mão, coxa e perna) durante o EPF em cicloergômetro. A TSlocal da testa foi maior que todas as outras regiões e a TSlocal do peito foi maior apenas que a da coxa. O número de GSA da testa foi maior do que em todas as outras regiões, e a GSA da mão foi maior que do peito, braço, coxa e perna. A TSlocal.GSA-1 da testa foi maior do que as do braço, antebraço, mão e coxa, e a TSlocal.GSA-1 das costas e do peito foram maiores que do antebraço e mão. A produção de suor da parte superior do corpo (testa, costas, peito, braço, antebraço, mão) foi maior que a inferior (coxa e perna). Concluiu-se que o EPF desencadeou um padrão de produção de suor maior na cabeça que pode estar relacionado à maior convecção nas regiões mais altas do corpo.