Cold water baths in winter have suddenly become a flex. From early-morning reels to wellness dares, they are often sold as proof of toughness and grea.

Cold water baths have gone from something a few eccentric athletes did in backyards to a full-blown wellness obsession.

We asked experts about how winter temperatures can affect your workout. Ask Well We asked experts about how winter temperatures can affect your workout. Credit...Eric Helgas for The New York Times ...