Thermoregulatory and perceptual responses of lean and obese fit and unfit girls exercising in the heat

Abstract

ObjectiveTo verify the thermoregulatory and perceptual responses of obese and lean girls, either fit or unfit, exercising in the heat at a similar rate of metabolic heat production per unit body mass. MethodsA total of 34 pubescent girls were allocated in four groups: 12 obese fit, 9 obese unfit, 5 lean fit, and 8 lean unfit. The obese groups (13.2±1.4 years, 40.5%±5.8% fat by DXA) differed in their aerobic fitness (V˙O2peak 76.0±8.1 vs. 56.6±5.8mL.kgmusclemass‐1.min−1), as well as the lean groups (13.1±1.6 years, 24.0%±4.8% fat) (V˙O2peak 74.5±2.9 vs. 56.2±5.0mL.kgmuscle mass−1min−1). Girls cycled two bouts of 25min with a 10min rest in between, at ∼5.4W.kg−1 in the heat (36°C and 40% relative humidity) and they were kept euhydrated. Rectal and skin temperatures and heart rate were measured every 5min. Perceptual responses were evaluated throughout the exercise. ResultsInitial rectal temperature was higher in the obese subjects compared to the lean subjects (37.5±0.3 and 37.2±0.3°C). No difference was observed among the girls whom were obese (eight fit or unfit) and lean (also fit or unfit) throughout the exercise in rectal temperature (37.6±0.2, 37.5±0.3, 37.5±0.3, 37.4±0.3°C, respectively), skin temperature (34.8±0.8, 35.1±1.0, 34.4±0.9, 35.2±0.9°C), and heart rate (128±18; 118±12, 130±16, 119±16beatsmin−1). No differences were observed in perceptual responses among groups. ConclusionRegardless of the adiposity or aerobic fitness, pubescent girls had similar thermoregulatory and perceptual responses while cycling in the heat at similar metabolic heat production.