Does cold showering or an ice bath speed up your metabolism?

During an ice bath or cold-water immersion your metabolism does shoot up, and this is measurable. In a study in which participants sat for one hour in water at 14°C, metabolism rose by approximately 350% relative to rest. This is accompanied by a strong release of stress hormones such as adrenaline. In lukewarm water at 20°C the rise was still around 93%. The problem: the moment you step out of the water, the effect is gone. You do burn a little extra during the ice bath itself, but there is no indication that this structurally speeds up your metabolism afterwards.

For people who take cold showers after strength training to recover better and build more muscle, there is an important downside. Multiple studies consistently show that regular cold water after training inhibits muscle growth. The anabolic signals in the muscle are suppressed, resulting in clearly less growth of the fast-twitch muscle fibres. Strength development suffers less, but if muscle growth is your goal, cold water after training works against you.

A frequently heard argument is that cold water reduces inflammation and thereby promotes recovery. However, biopsy research in humans shows that cold water after strength training does not affect the inflammatory response in muscle tissue any differently than a gentle cool-down cycle. In football players, regular cold or warm water after matches did not improve sprint performance, jump strength, or fitness any more than a sham treatment. And for muscle recovery after an injury, warm water (42°C) actually proved more effective than cold water.

If you want to take cold showers for the experience or as a mental boost, these studies give no reason to object. But do not count on a lasting acceleration of your metabolism, and if muscle growth is your goal, preferably avoid ice-cold showers after strength training.