Winter swimming: healthy or hazardous?. Evidence and hypotheses.

Swimming in cold water during the winter season is an extreme sport, with fans all over the world. However, its effects on health have been debated. This article examines the hypothesis that the effects of winter swimming may depend on previous exposure to cold stimuli. Immersion in cold water in unaccustomed persons may lead to detrimental consequences, while, in regular winter swimmers, adaptive physiologic mechanisms increase tolerance to cold. Furthermore, these mechanisms may prevent the occurrence of a wide variety of diseases. Prospective studies and epidemiological data are needed to test this hypothesis.