Responses of Obese and Lean Girls Exercising under Heat and Thermoneutral Conditions

Objective To compare thermoregulatory and perceptual responses between lean and obese girls during and after exercise under heat (HC) and thermoneutral (TC) conditions. Study design In a randomized order, 27 girls (14 lean [16.6 6.7% fat and 9.1 1.3 years] and 13 obese [41.3 6.7% fat and 9.4 1.1 years]) cycled 30 minutes at 55% peak oxygen uptake in 2 sessions, which only differed in the thermal conditions (35C and 40% relative humidity vs 24C and 50% relative humidity). Results Initial rectal temperature (Tre) was higher in obese versus lean during HC (37.5 0.3C vs 37.3 0.3C, P = .03) and TC (37.6 0.3C vs 37.3 0.2C; P = .03) sessions. During cycling, Tre remained higher in the obese, but the rate of increase was greater in the lean. This change occurred mainly in the HC, when final Tre of the lean surpassed that of the obese (37.8 0.2 vs 38.0 0.2C, P = .04). Sweat volume (in mL . m 2 ) was similar between lean and obese in the HC (167 119 and 120 145) and TC (200 196 vs 72 20). Heart rate, rate of perceived exertion, and thermal sensation were similar between groups, independent of the thermal condition. Cycling in HC produced decreased thermal comfort (P = .009) and increased irritation (P = .02) within the lean girls. Conclusion Thermoregulatory and perceptual responses of prepubescent obese girls during 30 minutes of cycling at a similar relative intensity do not seem to be impaired when comparing with a lean group either in TC or HC. (J Pediatr 2012;-:---).