Sauna and cold plunge: what they actually do

Saunas and cold plunges are wonderful rituals. The evidence for what they do is more modest than the marketing.

Heat

Long-running observational research from Finland found that people who used saunas more often had lower rates of cardiovascular death. That's an association, not proof the sauna caused it, but sauna bathing is generally considered safe for healthy adults and most people find it deeply relaxing.

Cold

Cold water immersion can reduce the feeling of soreness after hard exercise. But there's evidence that plunging immediately after strength training may blunt some of the muscle-building adaptations you trained for. If muscle is the goal, keep the plunge away from your lifting sessions.

What we'd say

• Enjoy them for how they make you feel, and for the hour of quiet.
• Hydrate, and get out if you feel dizzy or unwell.
• If you have heart disease, high or low blood pressure, are pregnant, or take medication that affects either, ask your doctor first.