Cold and Heat: Contrast Therapy Arrives

There is a moment, stepping from a hot sauna into a tub of near-freezing water, when the whole body protests at once. For a growing number of Delaware residents, that shock has become a sought-after ritual, as contrast therapy migrates from the training rooms of elite athletes into the general public.

The practice is simple in concept: alternate intense heat and intense cold, and let the body's responses do the rest. Adherents describe a rush of alertness and a lingering calm, and a small but growing body of research has lent the ritual a veneer of scientific respectability.

The businesses have moved quickly. Studios now sell access to sauna-and-plunge suites, and the once-solitary practice has become social, with groups gasping through the cold together and comparing notes afterward.

The claims sometimes outrun the evidence, and doctors urge caution for anyone with heart conditions. But the core experience needs little justification. Whatever it does for the body, the jolt of cold after heat delivers something people keep coming back for — a feeling of being vividly, unmistakably awake.