Adriano Detoni Filho

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 (35 °C and 40% relative humidity vs 24 °C and 50% relative humidity). RESULTS Initial rectal temperature (T(re)) was higher in obese versus lean during HC (37.5 ± 0.3 °C vs 37.3 ± 0.3 °C, P = .03) and TC (37.6 ± 0.3 °C vs 37.3 ± 0.2 °C; 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 ± 0.2 °C, 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.

Hydration and Perceptual Responses Resulting from a Training Session Involving Female Rhythmic Gymnastics Athletes

Young rhythmic gymnastics (RG) athletes engage in long training sessions that can lead to dehydration, especially on very hot days. Hydration status can affect the sporting performance and health maintenance of these young gymnasts. To evaluate the sweat volume, fluid balance and perceptual responses of young female RG athletes during a training session in the heat, fourteen female RG athletes (11.3±2.6 years) with a body fat percentage of 17.35±4.85% participated in this study. Body weight was measured and a urine sample collected for color analysis, both before and after the training session. The workout lasted 2.5 h in environmental conditions of between 29 °C and 50% relative humidity (RH), and 30 °C and 59% RH. Water was made available for consumption ad libitum and sweat volume was calculated from the change in body weight, corrected for water intake. The rate of perceived exertion, thermal sensation, thermal comfort, and irritability were measured every 30 minutes using categorical scales. Sweat volume was 1146.6±412.6 mL and water consumption was 825.2±368.1 mL. The negative fluid balance was between 1-2% in 50% and 1% in 42.8% of the athletes. Twelve athletes began the training session hypohydrated (urine color between 3 and 7), and 92.3% were hypohydrated after training (urine color between 4 and 6). There was an increase in thermal sensation (8±1) and discomfort (3±1) over the course of the workout. The RG athletes were unable to adequately replace their fluid losses, despite water being available for drinking ad libitum, which may reflect on the perceptual responses to heat.