European Journal of Applied Physiology

, Volume 108, Issue 4, pp 779–789 | Cite as

Critical environmental limits for exercising heat-acclimated lean and obese boys

  • Kelly Anne Dougherty
  • Mosuk Chow
  • W. Larry Kenney
Original Article

Abstract

Environmental limits for uncompensable heat stress, above which an imbalance between heat gain and heat loss forces body core temperature upward (i.e., the upper limits of the prescriptive zone), are unknown for children. To determine these limits, 7 lean and 7 obese 9- to 12-year-old heat-acclimated boys performed four randomized trials each on separate days to determine the critical water vapor pressure (Pcrit) forcing an upward inflection of body core temperature at several ambient temperatures. Subjects walked continuously on a treadmill at 30% maximal aerobic capacity at a constant dry bulb temperature (Tdb = 34, 36, 38 or 42°C). After a 30-min equilibration period at 9 torr, ambient water vapor pressure increased approximately 1 torr every 5-min until a distinct breakpoint in the core temperature versus time curve was evident. Compared to the lean subjects, obese subjects had significantly lower environmental limits (P < 0.03) in warm environments (Pcrit, for lean vs. obese, respectively = 32.9 ± 0.7 vs. 30.3 ± 0.8 torr at Tdb = 34°C; 29.6 ± 0.6 vs. 27.2 ± 0.9 torr at Tdb = 36°C; 27.8 ± 0.6 vs. 24.7 ± 0.9 torr at Tdb = 38°C; 25.5 ± 0.7 vs. 24.5 ± 1.5 torr at Tdb = 42°C). These results suggest that separate critical environmental guidelines should be tailored to lean and obese children exercising in the heat.

Keywords

Children Thermoregulation Prescriptive zone Psychrometric chart Heat balance 

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Kelly Anne Dougherty
    • 1
  • Mosuk Chow
    • 2
  • W. Larry Kenney
    • 3
  1. 1.Division of Gastroenterology, Hepatology and Nutrition, Department of PediatricsChildren’s Hospital of PhiladelphiaPhiladelphiaUSA
  2. 2.Department of StatisticsThe Pennsylvania State UniversityUniversity ParkUSA
  3. 3.Noll Laboratory, Department of KinesiologyThe Pennsylvania State UniversityUniversity ParkUSA

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