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Flavia Meyer, Oded Bar-Or and Boguslaw Wilk

Twelve 9- to 12-year-old children performed four exercise-in-the-heat trials (35 C°, 45% RH), which differed in the fluids consumed. In each trial, subjects were kept euhydrated while cycling one 20-min and two 15-min bouts at 50% peak VO2 followed by a 90% peak VO2 bout until exhaustion. Thereafter, they could drink ab libitum while resting. One drink was water, and the other three drinks had 6% CHO with different Na+: 0, 8.8, and 18.5 mEq · L1. All drinks had the same grape flavor. The perceived thirst was similar among trials and it did not increase while subjects were exercising. On average, subjects felt their stomach “somewhat full” with no difference among drinks. Thermal sensations, RPE, and overall comfort were similar among trials. During a 30-min recovery, volume intake was similar among drinks (201 ± 27 ml). In conclusion, the drink composition did not affect perceptual responses to drinking while euhydrated children exercised in the heat, nor did it affect drinking behavior during recovery.

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Flavia Meyer, Oded Bar-Or, Avi Salsberg and Dennis Passe

This study examined changes in children's thirst and drink preferences during exercise-induced hypohydration and their spontaneous rehydration during a 30-min recovery. Twenty-four 9- to 13-year-old children (14 females, 10 males) participated in four intermittent 90-rnin cycling sessions in the heat (35 C°, 20% relative humidity); the sessions differed in the drinks the children were sampling (apple, orange, water, and grape). Thirst and drink preferences were assessed (analog and category scales) while children dehydrated up to about 0.76% of their initial body weight. During 90 min dehydration, there was an increase in thirst intensity for all drinks. The grape was the preferable drink throughout the dehydration phase, but its desirability did not increase as much as the desirability of the orange, apple, and water drinks. During the 30-min recovery, most subjects rehydrated spontaneously, exceeding baseline levels by 0.76 ± 0.15% (M ± SEM) for grape, 0.40 ± 0.15 for apple, 0.71 ± 0.18 for orange, and 0.48 ± 0.16 for water. Although full rehydration was achieved with all drinks, the magnitude of rehydration was statistically greater with grape and orange than water and apple (p < .05). It was concluded that mild hypohydration during exercise increased children's thirst and drink desirability. In general, spontaneous overshoot of fluid consumption occurred during recovery.

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Simone D. Henkin, Paulo L. Sehl and Flavia Meyer

Because swimmers train in an aquatic environment, they probably do not need to sweat as much as runners who train on land and, therefore, should not develop the same magnitude of sweating adaptations.


To compare sweat rate and electrolyte concentration in swimmers, runners and nonathletes.


Ten swimmers (22.9 ± 3.1 years old), 10 runners (25 ± 2.9 y) and 10 nonathletes (26.5 ± 2.2 y) cycled in the heat (32°C and 40% relative humidity) for 30 min at similar intensity relative to their maximal cycle test. Sweat volume was calculated from the difference of their body mass before and after cycling, since they were not allowed to drink. Sweat was collected from the scapula using absorbent patch placed on the skin that was cleaned with distilled water. After cycling, the patch was transferred to syringe and the sample was obtained when squeezing it to a tube. Concentration of sodium ([Na+]), chloride ([Cl–]) and potassium ([K+]) were analyzed using an ion selector analyzer.


The sweat volume, in liters, of swimmers (0.9 ± 0.3) was lower (P < .05) than that of runners (1.5 ± 0.2) and similar to that of nonathletes (0.6 ± 0.2). [Na+] and [Cl-], in mmolL-1, of swimmers (65.4 ± 5.5 and 61.2 ± 81), and nonathletes (67.3 ± 8.5 and 58.3 ± 9.6) were higher (P < .05) than those of runners (45.2 ± 7.5 and 38.9 ± 8.3). [K+] was similar among groups.


The lower sweat volume and higher sweat [Na+] and [Cl-] of swimmers, as compared with runners, indicate that training in the water does not cause the same magnitude of sweating adaptations.

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Orlando Laitano, Jocelito Martins, Rita Mattiello, Claudia Perrone, Gilberto B. Fischer and Flavia Meyer

This study assessed sweat electrolyte concentration and losses in asthmatic children during exercise in the heat. Eleven asthmatics (AG; 11 ± 2 years old) and 11 nonasthmatics (CG; 10 ± 1 year old) underwent a maximal progressive cycle-ergometer test. During a second session, participants cycled in the heat (35°C, 60% RH) of a climatic chamber for 30 min at 50–60% of maximal workload. Sweat was collected using sweat patches attached to the dorsal region. No differences were observed in sweat [Na+] (AG = 35 ± 12.9 and CG = 43.4 ± 18 mmol/L) and [Cl-] (AG = 27.3 ± 10.4 and CG = 38.5 ± 19.1 mmol/L). There was no difference in sweat Na+ losses (AG = 0.47 ± 0.36 and CG = 0.66 ± 0.68 mmol/kg/h) and Cl- losses (AG = 0.37 ± 0.29 and CG = 0.59 ± 0.62 mmol/kg/h) between groups. Asthmatic children did not differ from nonasthmatics in their sweat electrolyte concentrations and electrolyte losses.