Resumen de Do Older Females Store More Heat than Younger Females during Exercise in the Heat?.
Joanie Larose, Glenn P. Kenny, Heather E. Wright, Ronald J. Sigal, Pierre Boulay, Stephen G. Hardcastle
AB Introduction: 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. Purpose: 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. Methods: 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[spacing dot above]O2max) (Y, 36.7 +/- 6.8 mL O2[middle dot]kg-1[middle dot]min-1; O, 33.8 +/- 8.0 mL O2[middle dot]kg-1[middle dot]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[degrees]C and 20% relative humidity. Each exercise bout was separated by 15 min of rest. Results: 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). Conclusion: 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
