THERMOREGULATION AND FLUID BALANCE IN CHILDREN EXERCISING IN THE HEAT

Open Access
Author:
Dougherty, Kelly A
Graduate Program:
Kinesiology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 06, 2008
Committee Members:
  • William Lawrence Kenney Jr., Committee Chair
  • James Anthony Pawelczyk, Committee Member
  • David E Conroy, Committee Member
  • Leann L Birch, Committee Member
Keywords:
  • Body Composition
  • Heat-Related Illnesses
  • Core Temperature
  • Hydration
  • Boys
  • Sport
Abstract:
Numerous factors could affect a child’s physical performance, subjective comfort and / or physical well-being during exercise in the heat, including hydration status, degree of heat acclimatization / acclimation, and severity of environmental conditions. However, there is a dearth of empirically-based information examining the impact of these factors on the physiological and subjective responses of children exercising in the heat. This series of studies was designed to: 1) determine the effect of 2% (DEH) and 6% carbohydrate-electrolyte solution (CES) euhydration (EUH) compared with placebo (P) EUH on basketball skill performance in highly skilled young players; 2) determine the degree of natural acclimatization and artificially-induced acclimation-related changes during repeated exercise / heat bouts in 7 lean and 7 obese 9- to 12-yr-old boys during the summer months; and 3) determine the critical environmental limits for uncompensable heat stress, above which an imbalance between heat gain and heat loss forces body core temperature (Tc) upward for exercising, heat-acclimated lean and obese 9- to 12-yr-old boys. Results from the first study suggest that in skilled 12- to 15-yr-old basketball players, deterioration in basketball skill performance accompanies 2% dehydration and EUH with a 6% CES significantly improves shooting performance and on-court sprinting over EUH with water. Findings from the second study suggest that obese compared to lean children are less naturally heat-acclimatized as indicated by significantly higher baseline Tc and display a significantly slower rate of decrease in exercise Tc and less of an elevation in sweating rate during repeated exercise / heat bouts. Results from the third study suggest that during light-to-moderate intensity exercise in a warm environment, the critical environments for heat-acclimated obese vs. lean 9- to 12-yr-old children are shifted downward on a psychometric chart, toward a lower critical water vapor pressure. The critical water vapor pressure was identified by a continuous rise in Tc and was defined as the critical ambient water vapor pressure above which thermal balance could not be maintained during exercise. Therefore, separate critical environmental guidelines should be tailored to lean and obese children exercising in the heat.