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Med Sci Sports Exerc. 2013 Dec;45(12):2265-76. doi: 10.1249/MSS.0b013e31829d24cc.

Do older females store more heat than younger females during exercise in the heat?

Author information

1Human and Environmental Physiology Research Unit, Faculty of Health Sciences, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, CANADA; 2Clinical Epidemiology Program, Ottawa Health Research Institute, Ottawa, Ontario, CANADA; 3Faculties of Medicine and Kinesiology, Departments of Medicine, Cardiac Sciences and Community Health Sciences, University of Calgary, Calgary, Alberta, CANADA; 4Faculty of Physical Education and Sports, University of Sherbrooke, Sherbrooke, Quebec, CANADA; and 5CanmetMINING, Natural Resources Canada, Sudbury, Ontario, CANADA.



Aging is associated with a reduction in the body's capacity to dissipate heat. To date, few studies have examined age-related changes in thermoregulatory function during short exercise periods in the heat in older females.


This study aimed to investigate the effects of age on whole-body heat loss during intermittent exercise in the heat in young and older females.


Direct and indirect calorimetry was used to measure whole-body evaporative heat loss (EHL), change in body heat content, and metabolic heat production. Eleven young (Y) (mean ± SD age = 24 ± 4 yr) and 13 older (O) (51 ± 8 yr) females matched for body surface area (Y, 1.72 ± 0.15; O, 1.75 ± 0.12 m²) and fitness (V(˙)O(2max)) (Y, 36.7 ± 6.8 mL O₂·kg⁻¹·min⁻¹; O, 33.8 ± 8.0 mL O₂·kg⁻¹·min⁻¹) performed four bouts of 15-min cycling (Ex1, Ex2, Ex3, and Ex4) at a constant rate of heat production (300 W) at 35°C and 20% relative humidity. Each exercise bout was separated by 15 min of rest.


EHL was reduced in O compared with Y during Ex1 (O, 199 ± 6 W; Y, 240 ± 9 W; P = 0.001), Ex2 (O, 238 ± 4 W; Y, 261 ± 9 W, P = 0.023), and Ex3 (O, 249 ± 4 W; Y, 274 ± 11 W; P = 0.040). EHL was not different between groups during Ex4 or during the recovery periods. Older females had a greater change in body heat content compared with young females (O, 270 ± 20 kJ; Y, 166 ± 20 kJ; P = 0.001).


These findings suggest that older females have a lower capacity for whole-body EHL compared with younger females during short intermittent exercise in the heat performed at a fixed rate of metabolic heat production.

[Indexed for MEDLINE]

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