Cold water after a sauna: plunges, sea dips and contrast

The short answer

Cold water causes a short-lived increase in inflammation markers, may lower stress the following day and slightly eases muscle soreness after exercise. A cold end to your shower was linked with 29% fewer sick days in one large trial. The big risk is cold water shock, a gasp-and-panic reflex that can be fatal in open water.

On this page

How strong is the evidence for cold water?
What does cold water do to the body?
How do you do it safely?
Common questions
References

How strong is the evidence for cold water?

Claim	Grade	Why
Less muscle soreness after exercise	Moderate	Meta-analyses of randomised trials find a small benefit over resting, best at 10–15°C for 10–15 minutes.
Fewer sick days	Weak	One large Dutch trial of cold-finish showers found 29% less sickness absence but no fewer illness days.
Lower stress	Weak	A 2025 meta-analysis found lower stress 12 hours after cold immersion, but not at other times, and no effect on mood.
Recovery with hot and cold contrast	Weak	Better than resting in trials with a high risk of bias, but no better than other recovery methods.
Weight loss and brown fat	Weak	Winter swimmers burn more energy in the cold, but no trial shows meaningful weight loss.
Immunity	Weak	Claims rest on small studies and the sick-days trial above.

What does cold water do to the body?

The moment cold water hits your skin, blood vessels clamp shut, you gasp, your breathing rate jumps and your heart rate and blood pressure spike. This is the cold shock response, and it peaks in the first minute. It eases with repeated dips, on average after about four. Stay in longer and your skin and then your muscles cool, which is what may help sore muscles but eventually leads to weakness and, much later, hypothermia.

How do you do it safely?

Start with a cool shower, not a plunge.
Enter slowly, breathe out, and wait for your breathing to settle before you go further.
Keep it short: 30 seconds to 3 minutes is plenty for most people.
Never go into open water alone, and stay where you can stand.
Skip it if you have a heart condition, uncontrolled blood pressure or Raynaud’s, or have been drinking.

Read cold water shock before your first sea or lake dip.

In this section

Cold plunge benefits: what the evidence says
Cold plunges and ice baths, graded: muscle soreness, stress, sick days, inflammation and brown fat, plus the downside for muscle gains.
Weak
Contrast therapy: does switching hot and cold work?
Hot-cold contrast therapy explained: what trials show for recovery and soreness, what it does to your circulation, and a safe routine.
Weak
Cold water shock: the risk after a sauna and how to stay safe
What cold water shock is, why it can be deadly in open water, who is most at risk and how to dip safely after a sauna in UK seas, lakes and rivers.

Common questions

Do you have to do a cold plunge after a sauna?

No. A cool shower or fresh air works fine. The long-term Finnish sauna studies didn't depend on cold plunges, and cold water carries risks of its own.

How cold should a cold plunge be?

Studies mostly used water between 7°C and 15°C. For muscle soreness, 10°C to 15°C gave the best results. Colder water is not more effective and is riskier.

Is wild swimming after a sauna safe?

It can be, with care. Go in slowly, never alone, stay close to the shore, keep it short and know how to float if cold shock hits. Avoid it if you have a heart condition or have been drinking.

References

First published 4 November 2026. Spotted an error? Tell us and we'll correct it. Read our editorial policy.