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Get Started Get in. Three minutes. Breathe. You’ve probably seen it in a thousand social media clips, usually filmed in a garden or a gym car park, with someone lowering themselves into a tub of icy water straight after a training session. It could have been Wim Hof, Harry Styles, Lady Gaga or any number of other well knowns.
Saunas have followed the same path. Common in exclusive spas and Scandinavian holidays, they’re now next to the weights room in a growing number of gyms, and recovery studios offering heat and cold therapy have opened on high streets everywhere.
But how helpful are they? The research will tell us. In short, cold water helps with some things and gets in the way of others, depending on what your client is training for. Heat has a strong long-term health story behind it but is much weaker when it comes to performance.
A client has no doubt seen it online. A podcast guest swears by a morning plunge, a footballer posts a picture from an ice bath, or a friend has bought a cold tub for the garden.
The claims are broad. Faster recovery, less soreness, better mood, stronger immunity, more fat burning and a longer life are the most common. Some of these have reasonable evidence behind them, some less so.
Researchers at the University of Portsmouth’s Extreme Environments Laboratory, one of the leading UK groups in this area, reviewed the whole field of cold water immersion as both a hazard and a treatment (Tipton et al., 2017). They concluded that the evidence for the different claims varies widely. In most cases there is a credible rationale, but in some the supporting data remain at the level of anecdote.
This is the starting point for our conversation today. The question is less “does it work?” and more “what’s it supposed to be doing for you?”
Cold water immersion has a long history in sport, and some of the claims are interestingly, true.
The most recent and broadest summary is a 2026 umbrella review that pulled together 15 systematic reviews with meta-analyses, covering 161 individual studies (Berjisian et al., 2026). It found that cold water after exercise reduced muscle soreness for up to 96 hours and lowered a blood marker of muscle damage over the following one to three days.
It also found improvements in muscular power 24 hours after high-intensity exercise, and 24 to 48 hours after the kind of lowering-heavy eccentric exercise that tends to cause the most soreness. Jump performance was better one to two days later too, although it was worse in the first few hours after getting out of the water.
The protocols that seemed to work best were 10 to 15 minutes in water at around 10 to 15°C, or slightly colder at 5 to 10°C. That is cold, but a long way from the near-freezing water in many online videos.
But, and it’s a big but… the review also had something to say about quality of the research. Most of the underlying reviews were rated low or critically low, and the certainty of evidence was low to very low. The direction of the findings is consistent enough to be useful, but the exact numbers are what we need to question.
Here is the part most marketing leaves out. The same umbrella review found that cold water did not improve strength, and that used regularly it impaired gains in strength and muscle size.
The single best study behind that finding comes from a research team in Australia and Norway (Roberts et al., 2015). Twenty-one active men strength trained twice a week for 12 weeks. After every session, half of them sat in cold water for ten minutes and half did a light active recovery on an exercise bike.
The active recovery group gained more strength and more muscle. Their type II muscle fibres, the fast fibres that respond most to heavy training, grew in size by 17 per cent, and the number of nuclei in each fibre, which supports growth, rose by 26 per cent. In the cold water group, neither changed significantly.
A second part of the study took muscle samples from nine men in the days after a single training session. Cold water blunted the activity of the satellite cells and signalling proteins that drive muscle repair and growth over the following two days.
A meta-analysis pooling the training studies reached the same conclusion (Malta et al., 2021). Regular cold water immersion after resistance training reduced gains in maximal strength, strength endurance and explosive, ballistic performance. When it followed endurance training, there was no clear effect on aerobic fitness or time-trial performance.
The likely explanation is that the inflammation and increased blood flow after a hard session are part of the signal that tells muscle to adapt. Cooling the muscle straight afterwards dampens that response. It feels better, but some of the message the training was trying to send gets lost.
That leads to a simple rule of thumb. If a client is lifting to build strength or muscle, keep cold water well away from those sessions. If they enjoy a cold dip for how it makes them feel, it fits better on a rest day or several hours away from strength training.
The picture is different for a client in a heavy season of matches, races or competition, where the next performance a day or two later is what counts. In that situation, the short-term gains in soreness and power can outweigh a small loss of long-term adaptation. That is the situation cold water suits best.
Sauna has one of the most quoted long-term health findings in exercise science. It comes from the Kuopio Ischaemic Heart Disease Risk Factor Study, which followed 2,315 middle-aged men from eastern Finland for a median of more than 20 years (Laukkanen et al., 2015).
Compared with men who used a sauna once a week, those who used one four to seven times a week had a 63 per cent lower risk of sudden cardiac death after adjustment for other risk factors. Similar patterns were seen for fatal heart disease, fatal cardiovascular disease and death from any cause. Longer sessions, of more than 19 minutes, were linked with lower risk of sudden cardiac death than sessions of under 11 minutes.
There are two important caveats here that we have to mention. This was an observational study, so it shows a link rather than proof that sauna use caused the lower risk. People who use a sauna most days may differ from those who do not in ways that are hard to measure. And the participants were Finnish men in the 1980s, for whom sauna use is a lifelong cultural habit rather than a new trend.
Even so, it is a strong enough association to think there may be something in it, and it fits with what we know about heat raising heart rate and widening blood vessels in a way that resembles moderate exercise.
When it comes to sports performance, the evidence for heat is lacking. A 2025 systematic review gathered every trial on whole-body heat exposure after exercise, using saunas or hot water immersion (Ahokas et al., 2025).
Fourteen studies with 194 participants met the criteria. Of the nine that looked at short-term recovery, four found no effect, four found a benefit and one found heat made recovery worse. The five longer training studies suggested post-exercise heat may improve running performance, at least in hot conditions, but repeated heat had no effect on cycling performance or VO2 max, a measure of aerobic fitness.
The authors concluded that it is not yet possible to draw firm conclusions about heat for recovery or performance. The evidence quality was low to moderate and the studies used very different methods.
So the honest answer is that heat is unlikely to harm a client’s training and may help with heat acclimatisation, which is useful before a summer race or a holiday abroad. It is not yet a proven recovery tool. So if it makes you feel good… why not!
For clients who want to add sauna sessions to their week, a few simple guidelines keep it safe and useful.
The Finnish study compared sessions of under 11 minutes, 11 to 19 minutes and more than 19 minutes, and most of the men used the sauna two or three times a week. Clients new to it should start with shorter sessions and build up, leaving if they feel dizzy or unwell.
Fluid is of course the obvious thing to mention. A hot sauna can cause noticeable sweat loss, so drinking water before and after is sensible, especially if the client has just trained. Standing up slowly at the end helps too, because the widening of blood vessels in the heat can make some people light-headed.
Timing is more flexible than with cold water. There is no clear evidence that a sauna after lifting reduces muscle gains, so clients who enjoy one after their session can usually carry on. The bigger risk is a very long, very hot session straight after a hard workout leaving them drained.
Cold water is not risk-free, and this is where a coach’s advice can make a big difference. The Portsmouth review covers cold water as a precursor to drowning, cardiac arrest and hypothermia, as well as a treatment (Tipton et al., 2017).
The first minute or so of sudden immersion triggers the cold shock response, a gasp followed by rapid, uncontrolled breathing and a jump in heart rate and blood pressure. In open water, that gasp is a recognised cause of drowning. In a tub or plunge pool, it is a reason to get in slowly and never alone.
Clients with heart conditions, high blood pressure, Raynaud’s or who are pregnant should speak to their GP before starting cold water immersion. The same applies to sauna use for clients with heart conditions, low blood pressure or who are pregnant. Alcohol and either extreme of temperature do not mix.
When a client tells you they have started ice baths or saunas, a handful of questions will tell you most of what you need to know.
What are you hoping it will do for you? If the answer is faster muscle gain, the evidence points the other way for cold water. If it is feeling less sore before a match or simply feeling good, it may well fit.
When are you doing it? Straight after a strength session is the timing most likely to get in the way. First thing in the morning on a rest day is going to achieve what you want.
How cold, and for how long? Water at 10 to 15°C for 10 to 15 minutes is plenty. Colder and longer is not automatically better and increases the risk.
Do you do it on your own? Anyone getting into very cold water should have someone nearby, especially in the first few sessions.
And has anything changed in your health? New medication, a heart condition, high blood pressure or pregnancy all mean it is time to check with a GP first.
The table below gives a quick way to match heat and cold to what a client is training for.
| Client Goal | Cold Water | Heat |
|---|---|---|
| Building strength or muscle | Avoid straight after lifting. Fine on rest days or several hours away from training | Fine to use. Little evidence either way for muscle growth |
| Competing again within 24 to 48 hours | Can reduce soreness and help power and jump performance recover | Mixed evidence for short-term recovery |
| Endurance training | No clear harm to aerobic fitness. Useful in hot conditions | May help running performance in the heat |
| Long-term heart health | Limited evidence | Strong observational link with lower cardiovascular risk |
| Feeling good and relaxing | A reasonable choice if the client enjoys it and uses it safely | A reasonable choice if the client enjoys it and uses it safely |
It would be a shame if recovery is just thought of in terms of hot and cold therapy. There are many other things we can do which help far more.
Sleep is the biggest one. A client who sleeps well will recover better than anyone who sleeps badly and plunges every morning. Eating enough protein and energy to support training comes next, followed by sensible programming that gives muscle groups enough time between hard workouts.
Movement helps too. The active recovery group in the Roberts study did nothing more exotic than light cycling, and they showed better markers of recovery. Gentle movement and walking on rest days is a simple yet effective recovery activity and support training rather than compete with it.
Hands-on work is also effective. As we covered in our article Massage or Movement? What the Evidence Says About DOMS, sports massage changes how sore a client feels after hard training, while active recovery does even more. Feeling less sore is often what a client is really looking for when they ask about an ice bath, and a skilled massage therapist can give them that on the same day as a heavy workout.
Put together, a coach who can programme sensibly, prescribe the right kind of easy movement and offer hands-on soft tissue work has most of the recovery toolkit a client needs.
Many of us find our clients have already made up their minds about heat and cold before they ask us. They have bought the tub, booked the sauna sessions or joined a recovery studio, and they want to know how to fit it in.
From our research, we know if the goal is strength or muscle, keep cold water away from training sessions. If the goal is competing again soon, cold water can help with soreness and power in the short term. Saunas have a strong long-term health association and a weaker performance story, and they are generally safe for healthy clients.
Above all, make sure the fashionable extras don’t overshadow the basics. Sleep, nutrition, sensible programming and plenty of easy movement will always do more for recovery than any tub of ice.
Ahokas, E.K., Hennessy, R.S., Hanstock, H.G., Kyröläinen, H. and Ihalainen, J.K. (2025). Effects of post-exercise heat exposure on acute recovery and training-induced performance adaptations: a systematic review. Sports Medicine – Open, 11(1), 106. Click here to review the full research article.
Berjisian, E., Miraftabi, H., Ihsan, M., Homer, K.A., Kendall, K., Roberts, L. and Abbiss, C. (2026). Strategic application of post-exercise cold-water immersion to enhance performance recovery and adaptation: an umbrella review of 15 published systematic reviews with meta-analysis. Sports Medicine – Open, 12(1). Click here to review the full research article.
Laukkanen, T., Khan, H., Zaccardi, F. and Laukkanen, J.A. (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine, 175(4), pp.542-548. Click here to review the full research article.
Malta, E.S., Dutra, Y.M., Broatch, J.R., Bishop, D.J. and Zagatto, A.M. (2021). The effects of regular cold-water immersion use on training-induced changes in strength and endurance performance: a systematic review with meta-analysis. Sports Medicine, 51(1), pp.161-174. Click here to review the full research article.
Roberts, L.A., Raastad, T., Markworth, J.F., Figueiredo, V.C., Egner, I.M., Shield, A., Cameron-Smith, D., Coombes, J.S. and Peake, J.M. (2015). Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training. The Journal of Physiology, 593(18), pp.4285-4301. Click here to review the full research article.
Tipton, M.J., Collier, N., Massey, H., Corbett, J. and Harper, M. (2017). Cold water immersion: kill or cure? Experimental Physiology, 102(11), pp.1335-1355. Click here to review the full research article.
Clients asking about ice baths and saunas are really asking how to recover better, move better and feel less beaten up after training. That is a question a personal trainer with hands-on and movement skills can answer far better than any tub of cold water.
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