Thermoregulation And Perception Among Lean/obese And Fit/unfit Girls Cycling In The Heat: 1409 Board #217 May 31 8 00 AM - 9 30 AM

Heat stress may be an extra concern to obese and unfit adolescents while exercising. Besides the higher rate of body temperature (Tbody) increase, it is believed that heat stress aggravates perceived exertion (RPE), irritability and thermal sensations. However, no study has compared thermoregulatory and perceptual responses of obese and unfit girls in relation to their lean and fit peers under similar heat stress and metabolic heat production. PURPOSE: To verify thermoregulatory and perceptual responses of obese and lean girls, either fit or unfit, exercising in the heat at a similar metabolic heat production per unit of body mass (Hp). METHODS: 34 pubescent (Tanner 2 to 4) girls divided in four groups participated in the study. 21 were obese (12 fit and 9 unfit; 13.2±1.4yrs, 60.8±13.7kg, 158±0.1cm, 40.5±5.8% fat (DXA), VO2peak 76.0±8.1 and 56.6±5.8 ml.kg.musclemass-1. min-1), and 13 lean (5 fit and 8 unfit; 13.1±1.6yrs, 44.1±6.5kg, 156±0.1cm, 24.0±4.8% fat, VO2peak 74.5±2.9 and 56.2±5.0 ml.kg.musclemass-1.min-1). They cycled 2×25 min bouts, with a 10-min rest, at ~5.4 W.kg-1 (5.2±1.2 and 5.7±1.0 W.kg-1, obese and lean) in the heat (36°C and 40% RH). Rectal (Tre) and skin (Tsk) temperatures and heart rate (HR) were measured every 5 min. Additionally, RPE, irritability, thermal sensation, and thermal comfort were collected throughout the exercise. Sweat losses were replenished with spring water during rest period. RESULTS: Initial T and HR were similar between obese and lean girls (37.5±0.3 and 37.2±0.3°C and 101±13.6 and 98.8±11.9 bpm). No difference was observed among the 4 groups (obese fit, obese unfit, lean fit and lean unfit) throughout the exercise for Tre: 37.6±0.2, 37.5±0.3, 37.5±0.3 and 37.4±0.3 °C; T 34.8±0.8 ; 35.1±1.0 ; 34.4±0.9 e 35.2±0.9°C; T : 37.0±0.2, 37.0±0.4, 36.8±0.3 and 36.9±0.3 °C; HR: 128±18; 118±12, 130±16 and 119±16 bpm. Also, no differences were observed in the perceptual responses (RPE:11±2, 12±2, 11±2 and 11±2, irritability: 3±0.5, 2±0.3, 3±0.8 and 2±0.3, thermal sensation: 7±0.4, 7±0.5, 7±0.7, 6±0.7 and thermal comfort: 3±0.4, 3±0.5, 3±0,7 and 3±0.5). CONCLUSION: Regardless of the adiposity or aerobic fitness level, pubescent girls had similar thermoregulatory and perceptual responses while cycling under heat stress during 50 min at a mild (~5,4 W.kg-1) intensity level.