The short answer
Alternating hot and cold water eased muscle soreness and strength loss after exercise better than resting in a review of 18 trials, but all had a high risk of bias and contrast was no better than other recovery methods. Going from a sauna to cold water strains the heart briefly, so build up slowly and skip it if you have heart problems.
Weak evidence
Small or short studies, surveys, or results that are mixed. How we grade
On this page
What is contrast therapy?
Moving between heat and cold: a sauna or hot tub, then a cold plunge, shower or sea dip, then back again. It’s a centuries-old habit in Finland, Russia and Japan, and it’s the format of most of the new UK sauna clubs, many of which sit by the sea or a river.
In sports medicine, contrast water therapy usually means alternating hot and cold water baths for a minute or so each, several times over.
What does the research show?
A 2013 systematic review pooled 18 trials of contrast water therapy after hard exercise. Compared with passive rest, contrast therapy led to:
- less muscle soreness at every time point from 6 to 96 hours, and
- less loss of muscle strength.
But all 18 trials had a high risk of bias, and when contrast therapy was compared with other methods, including cold water alone, warm water, compression and active recovery, none clearly beat the others. So it seems better than doing nothing, and about as good as other options.
There are no good long-term trials of the sauna-and-sea routine for general health. Finnish winter swimmers who combine cold dips with saunas two or three times a week show signs of adapting to both heat and cold, but that tells us about physiology, not health outcomes.
What happens in your body when you switch?
- In the heat, blood vessels in your skin open wide, heart rate climbs and blood pressure, after a while, falls.
- In the cold, those vessels clamp shut within seconds. You gasp, breathe fast and your heart rate and blood pressure jump. This is the cold shock response.
- As you warm up again, the vessels reopen and you often feel a tingling glow.
That rapid switch is why many people find contrast so invigorating, and why it is a real strain on the heart for a minute or two.
A safe routine for beginners
- Sauna for 8 to 12 minutes.
- Cool shower for 30 seconds to a minute, gradually turning it colder over a few visits.
- Rest for 5 to 10 minutes, sitting down, with a drink of water.
- Repeat once or twice.
When you’re used to it, you can swap the shower for a plunge or a dip. Get in slowly, breathe out, and keep it short. Never dive or jump into cold water straight from a hot sauna.
Keep reading
- 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.
- 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
Common questions
Should I end on hot or cold?
There's no good evidence either way. Many people end with cold for alertness and warm up naturally afterwards; others end with heat to relax. In winter outdoors, finishing warm and dressing quickly is the safer choice.
How many rounds of contrast should I do?
Two or three rounds of sauna and cool-down is the traditional pattern. There's no evidence more rounds bring more benefit.
Is contrast therapy safe for the heart?
For healthy people, usually. The switch from heat to cold causes a sudden rise in heart rate and blood pressure. People with heart disease, uncontrolled blood pressure or a history of heart rhythm problems should avoid sudden cold plunges unless their doctor says otherwise.
References
- Bieuzen F, Bleakley CM, Costello JT. Contrast water therapy and exercise induced muscle damage: a systematic review and meta-analysis. PLoS One, 2013.pubmed.ncbi.nlm.nih.gov
- Søberg S et al. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine, 2021.pubmed.ncbi.nlm.nih.gov
- Heinonen I, Laukkanen JA. Effects of heat and cold on health, with special reference to Finnish sauna bathing. American Journal of Physiology, 2018.pubmed.ncbi.nlm.nih.gov
- Tipton MJ et al. Cold water immersion: kill or cure? Experimental Physiology, 2017.pubmed.ncbi.nlm.nih.gov
First published 4 November 2026. Spotted an error? Tell us and we'll correct it. Read our editorial policy.