Sauna and cold plunge.
Sauna and cold plunge: what contrast therapy does, and how to do it safely.
Sauna, then the sea or a cold plunge, then back into the heat: it’s how most seaside saunas in Ireland and the UK are used. Cold water does ease muscle soreness and may lower stress for a while. It can also strain your heart in the first minute, and it can blunt strength gains after training. Here’s what the studies show, and a routine that keeps it safe.
Updated · 7 min read
Sauna and cold plunge at a glance
Going from a hot sauna into cold water, then back again, is called contrast therapy. It’s how most seaside saunas in Ireland and the UK work, and how Finns have bathed for centuries with a lake or a roll in the snow. People do it because it feels extraordinary. The research on why, and on what it does for your health, is thinner than social media suggests.
- ModerateLess muscle soreness after exercise. Cold water beat rest in reviews of small trials.1,2
- EarlyFeeling less stressed and sleeping better. Short-term effects in a 2025 review of 11 trials.3
- EarlyFewer sick days. In one large trial of cold showers, though people were ill just as often.4
- CautionBuilding strength. Regular cold plunges after weight training reduced gains in one trial.5
- UntestedSauna and cold together. We found no trial that compared contrast bathing with sauna alone for long-term health.
The heat side has much more evidence than the cold. Regular sauna is linked to lower blood pressure and fewer deaths from heart disease, from studies that measured sauna alone.
What cold water does to your body
The first minute is the dangerous part. Sudden cold on the skin triggers the cold shock response: a gasp, fast uncontrolled breathing and a jump in heart rate and blood pressure. The Met Office says cold water shock can happen in water below 15°C, which in Ireland and the UK means the sea for most of the year.6 Water Safety Ireland warns that cold shock can lead to incapacitation and drowning in the first 2–3 minutes.7
Putting your face in cold water also triggers the diving response, which slows the heart. When both responses fire at once, the heart gets mixed signals. Researchers call this “autonomic conflict”. It causes irregular heartbeats in many healthy volunteers, and may explain some deaths put down to drowning.8
The good news is that the shock fades with practice. A 2024 review found the cold shock response settles after about four immersions, with heart rate around 14 beats a minute lower.9 That’s one reason regular cold-water swimmers find it easier than first-timers.
Cold plunge benefits: what the research shows
Muscle soreness
This is the best-studied use. A Cochrane review of 17 small trials found cold-water immersion (water below 15°C) reduced muscle soreness compared with rest, from 24 to 96 hours after exercise.1 Hot-and-cold contrast immersion did no worse or better than cold alone. A later meta-analysis found cold water “can be slightly better than passive recovery”, with the best results at around 10–15°C for 10–15 minutes.2 Another found less soreness but “no evidence” of faster recovery in objective measures such as strength.10 The trials were small and of low quality.
Strength training
If you lift weights to build muscle, be careful with the timing. In a 12-week trial, 21 men did 10 minutes in cold water or an active cool-down after each strength session. Those who did the active cool-down gained more strength and muscle, and the researchers said regular cold water after training “should be reconsidered”.5 A sauna or plunge on a rest day, or hours after training, avoids the question.
Stress, mood and sleep
A 2025 meta-analysis of 11 randomised trials with 3,177 people, in water at 7–15°C, found stress was lower 12 hours after cold immersion, but not at other times. Sleep quality and quality of life improved; mood didn’t change. Inflammation markers actually rose straight after, and an hour later.3 Promising, short-lived and still early.
Colds and sick days
In a Dutch trial, 3,018 adults finished their usual hot shower with 30, 60 or 90 seconds of cold for 30 days. They took 29% fewer days off sick, but they weren’t ill any less often: they seemed to cope better while ill.4
The “11 minutes of cold, 57 of heat” rule
This number comes from a Danish study of winter swimmers. Seven young men who swam in the sea at 1–9°C and used a sauna two or three times a week totalled about 11 minutes of cold and 57 minutes of heat a week.11 Those are the men’s habits, recorded in a table, not a dose the study tested or recommended.
Reviews of the wider research agree on the shape of it. One found “increasing scientific support” that cold water may have some health benefits, mostly from small studies.12 Another found that some popular claims remain “at the level of anecdotal speculation”.13
Does sauna then cold plunge add up?
Nobody has shown it yet. The long Finnish studies that linked frequent sauna with fewer heart deaths recorded sauna habits, not what people did afterwards.14 We found no trial comparing hot and cold with heat alone over months, and none testing whether to finish on cold or warm, or how many rounds to do. For the evidence on the heat itself, see our guide to sauna health benefits.
What contrast bathing reliably gives you is the feeling: the rush of the cold, the warmth flooding back in the sauna, and the calm afterwards. That’s reason enough for most people, as long as they do it safely.
How to do contrast therapy safely
- Heat10–15 minutes in the sauna, or less if you’re new. Leave if you feel dizzy.
- ColdWalk in, don’t jump. Control your breathing before anything else. 30 seconds to 2 minutes is plenty at first.
- RestDry off, sit and drink water until you feel normal again.
- RepeatTwo or three rounds, if you feel well. Many people end on cold; others prefer to end warm. No study says which is better.
- Get in slowly, and keep your face out at first. Splash your face and neck to get used to it, as Water Safety Ireland advises.15
- Breathe before anything else. The gasp and fast breathing pass within a minute or so if you stay calm and still.
- Never plunge or swim alone, and have someone on shore watching if you’re in the sea.15
- No alcohol before or between rounds.
- Warm up afterwards with dry clothes and a warm hat.15 Your temperature can keep falling for a while after you get out, so don’t drive straight away if you’re shivering hard.
Cold plunge in the sea: what to expect
Average sea temperatures around the UK and Ireland range from about 6–10°C in winter to 15–20°C in summer, according to the Met Office. Lakes and rivers are often colder.6 So most sea dips after a sauna count as cold-water immersion all year round.
| Temperature | Time in the water | |
|---|---|---|
| Irish and UK sea in winter | 6–10°C | Most seaside sauna guests stay in for under 2 minutes |
| Irish and UK sea in summer | 15–20°C | Not cold enough to count as a cold plunge in most studies |
| Trials on muscle soreness | Under 15°C, best at 10–15°C | 10–15 minutes |
| Trials on stress and wellbeing | 7–15°C | From 30 seconds to 2 hours |
| Danish winter swimmers | 1–9°C | About 11 minutes a week in total |
If you get into trouble in cold water, the Met Office’s advice is to float to live: lean back, spread your arms and legs like a starfish and float until you can control your breathing, then call for help on 999 or 112.6 Lifeguards and cold-water instructors also teach the 1-10-1 rule: about 1 minute to get your breathing under control, about 10 minutes of useful movement before your muscles weaken, and up to an hour before cold makes you lose consciousness.16
Who should be careful
Cold shock raises heart rate and blood pressure sharply, and the mix of cold shock and the diving response can upset heart rhythm.8 Talk to your doctor before cold plunging if you have heart disease, high blood pressure, a heart rhythm problem or are pregnant. The same applies to the sauna. If you have Raynaud’s or poor circulation, keep your hands and feet out or skip the plunge.
How we wrote this page
We read the studies, reviews and official guidance linked below and checked every number on this page against its source. Where a figure we found only appeared in news coverage or on a seller’s site, we left it out or said so. Some popular claims about cold plunges, such as exact afterdrop times and fixed weekly doses, only appear in news coverage or social media. We left them out. We last checked the sources on 21 October 2026. Spotted something wrong? Email us.
Olladay makes booking software for saunas, so we’d like more people to use them. That’s a reason to be careful with claims, not to oversell them.
References
- Bleakley C, McDonough S, Gardner E, et al. Cold-water immersion (cryotherapy) for preventing and treating muscle soreness after exercise. Cochrane Database of Systematic Reviews. 2012;CD008262. 10.1002/14651858.CD008262.pub2
- Machado AF, Ferreira PH, Micheletti JK, et al. Can water temperature and immersion time influence the effect of cold water immersion on muscle soreness? A systematic review and meta-analysis. Sports Medicine. 2016;46(4):503–514. 10.1007/s40279-015-0431-7
- Cain T, Brinsley J, Bennett H, et al. Effects of cold-water immersion on health and wellbeing: a systematic review and meta-analysis. PLoS One. 2025;20(1):e0317615. 10.1371/journal.pone.0317615
- Buijze GA, Sierevelt IN, van der Heijden BCJM, Dijkgraaf MG, Frings-Dresen MHW. The effect of cold showering on health and work: a randomized controlled trial. PLoS One. 2016;11(9):e0161749. 10.1371/journal.pone.0161749
- Roberts LA, Raastad T, Markworth JF, et al. Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. Journal of Physiology. 2015;593(18):4285–4301. 10.1113/JP270570
- Met Office. Winter water safety. weather.metoffice.gov.uk/warnings-and-advice/seasonal-advice/travel/out-and-about/winter-water-safety
- Water Safety Ireland. Emergency situations. watersafety.ie/emergency-situations/
- Shattock MJ, Tipton MJ. ‘Autonomic conflict’: a different way to die during cold water immersion? Journal of Physiology. 2012;590(14):3219–3230. 10.1113/jphysiol.2012.229864
- Barwood MJ, Eglin C, Hills SP, et al. Habituation of the cold shock response: a systematic review and meta-analysis. Journal of Thermal Biology. 2024;119:103775. 10.1016/j.jtherbio.2023.103775
- Hohenauer E, Taeymans J, Baeyens JP, Clarys P, Clijsen R. The effect of post-exercise cryotherapy on recovery characteristics: a systematic review and meta-analysis. PLoS One. 2015;10(9):e0139028. 10.1371/journal.pone.0139028
- Søberg S, Löfgren J, Philipsen FE, et al. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine. 2021;2(10):100408. 10.1016/j.xcrm.2021.100408
- Espeland D, de Weerd L, Mercer JB. Health effects of voluntary exposure to cold water: a continuing subject of debate. International Journal of Circumpolar Health. 2022;81(1):2111789. 10.1080/22423982.2022.2111789
- Tipton MJ, Collier N, Massey H, Corbett J, Harper M. Cold water immersion: kill or cure? Experimental Physiology. 2017;102(11):1335–1355. 10.1113/EP086283
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine. 2015;175(4):542–548. 10.1001/jamainternmed.2014.8187
- Water Safety Ireland. Winter safety. watersafety.ie/wintersafety/
- Canadian Safe Boating Council. The 1-10-1 principle. csbc.ca/1-10-1-principle/
Questions
Is a cold plunge after the sauna good for you?
It is safe for most healthy adults and many people find it refreshing and calming. The evidence for health benefits is mostly for cold water and sauna separately: cold water eases muscle soreness and may lower stress for a few hours, and regular sauna is linked to better heart health. No long trial has tested the two together.
How long should you stay in a cold plunge?
For a first time, 30 seconds to 2 minutes is plenty. Trials on muscle soreness used 10–15 minutes at 10–15°C, but you do not need that long to feel the effect. Get out if you start shivering hard or your hands stop working.
Should you do the sauna or cold plunge first?
Most people warm up in the sauna first, then cool off, then go back in for two or three rounds. No study has compared finishing on cold with finishing warm.
What temperature should a cold plunge be?
Studies used water from about 7°C to 15°C. The Irish and UK sea is 6–10°C in winter and 15–20°C in summer. Colder is not better for beginners: the cold shock is stronger.
Is cold plunging bad after a workout?
For building strength and muscle, it may be. In a 12-week trial, men who took a 10-minute cold plunge after each strength session gained less than men who did an active cool-down. For soreness, cold water helped a little in reviews of small trials.
What is the 11 minutes cold and 57 minutes heat rule?
It comes from a small Danish study of seven winter swimmers, describing their usual weekly totals. The study did not test it or recommend it as a dose.
Is it dangerous to go from a sauna into cold water?
It can be for some people. Cold shock raises heart rate and blood pressure sharply, which is a risk with heart disease. Get in slowly, never alone, skip alcohol, and ask a doctor first if you have a heart condition or are pregnant.
What is contrast therapy?
Alternating heat and cold, usually a sauna followed by cold water or a cold shower, repeated two or three times. It is how most seaside saunas in Ireland and the UK are used.