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To the Editor.—
In the letter "Effect of Sweating" (1981;246:623), MAJ Ward Dean, MC, USA, claims that the loss of 500 g of sweat in a sauna consumes nearly 300 kcal. I would consider this highly doubtful, since extrapolating these figures would suggest that survival in a hot climate, where several liters of sweat may be lost daily, would require an increased caloric intake for this loss compared with the same daily activities in a more temperate zone, and clearly this does not happen.He also suggests that the regular use of a sauna may be as effective a means of cardiovascular conditioning as regular exercise. Since the improvement in cardiovascular efficiency associated with exercise is due mainly to peripheral (skeletal muscle) rather than myocardial changes, it is difficult to envisage how this can also be achieved by the inactivity of the sauna.