Heat, humidity safe for some young exercisers

NEW YORK (Reuters Health) - Young girls can tolerate vigorous exercise in a hot, humid environment as long as they are acclimated to the heat and consume enough liquid, research indicates.

The American Academy of Pediatrics has suggested that children may be less able to withstand physical activity in the heat because they sweat less than adults, and also have a smaller body surface area in relation to their body mass, Dr. Anita M. Rivera-Brown of the Center of Sports Health and Exercise Sciences in Salinas, Puerto Rico and colleagues note.

But past research by these investigators found that boys and girls acclimated to the heat sweated profusely and did not overheat and when exercising in hot and humid conditions.

The researchers hypothesized that active girls raised in a tropical climate would tolerate exercising under such conditions as well as adult women. To investigate, they had nine girls aged 9 to 12 and nine women between the ages of 20 and 34 perform a cycling exercise outdoors until they felt fatigued. All study participants lived in Puerto Rico and were thus acclimated to the heat and humidity, and all were active.

During the exercise, all participants were periodically given a sports drink containing carbohydrates and electrolytes.

There was no difference in sweating rate, temperature increase, heat storage, heart rate or blood flow between the girls and the adult women, the researchers found. Both groups cited fatigue in the legs and discomfort in the gluteus muscle as the chief reasons for stopping exercise due to fatigue.

The researchers conclude, based on this study, that being acclimated to heat and humidity, as well as ensuring adequate hydration, may play key roles in helping girls to tolerate exercise in these conditions.

SOURCE: International Journal of Sports Medicine, December 2006.