Thermoregulatory Efficiency is Increased after Heat Acclimation in Tropical Natives

Flávio C. Magalhães; Renata L. F. Passos; Michele A. Fonseca; Kenya P. M. Oliveira; João B. Ferreira-Júnior; Angelo R. P. Martini; Milene R. M. Lima; Juliana B. Guimarães; Valério G. Baraúna; Emerson Silami-Garcia; Luiz O. C. Rodrigues

doi:10.2114/jpa2.29.1

ORIGINALS

Thermoregulatory Efficiency is Increased after Heat Acclimation in Tropical Natives

Flávio C. Magalhães, Renata L. F. Passos, Michele A. Fonseca, Kenya P. M. Oliveira, João B. Ferreira-Júnior, Angelo R. P. Martini, Milene R. M. Lima, Juliana B. Guimarães, Valério G. Baraúna, Emerson Silami-Garcia, Luiz O. C. Rodrigues

Author information

Flávio C. Magalhães
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Laboratory of Biochemistry of Physical Activity, School of Physical Education and Sport, Department of Biodynamic of the Human Movement, University of São Paulo, Brazil
Renata L. F. Passos
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Michele A. Fonseca
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Kenya P. M. Oliveira
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
João B. Ferreira-Júnior
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Angelo R. P. Martini
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Milene R. M. Lima
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Juliana B. Guimarães
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Valério G. Baraúna
Laboratory of Biochemistry of Physical Activity, School of Physical Education and Sport, Department of Biodynamic of the Human Movement, University of São Paulo, Brazil
Emerson Silami-Garcia
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais
Luiz O. C. Rodrigues
Laboratory of Exercise Physiology, School of Physical Education, Physical Therapy and Occupational Therapy, Department of Physical Education, Federal University of Minas Gerais

Keywords: sweat function, heat acclimation, facilitated sweat evaporation

JOURNAL FREE ACCESS

2010 Volume 29 Issue 1 Pages 1-12

DOI https://doi.org/10.2114/jpa2.29.1

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Abstract

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 (40±0°C and 45.1±0.2% 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 (η_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/(H+R+C)). 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 p<0.05) and the sweat rates from the forehead and the chest showed a small nonsignificant increase (p=0.34 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 (32±5%) in comparison to the trunk (11±2%, p=0.001). After the heat acclimation period we observed higher w_sk and E_sw and reduced S/(H+R+C), 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/(H+R+C) (p<0.05 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.

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