Sauna After a Workout: Benefits, Safety and How Long to Stay In

The post-workout sauna has become a proper trend, helped along by the rise of community saunas across the UK. Social media will tell you heat speeds up recovery, builds endurance, burns fat and flushes out toxins. Some of that is loosely based on real research. Some of it is not. Here is what the evidence actually shows, how long and how hot to go if you are new to it, and how to fit it around your training week.

What does a sauna actually do to your body?

A traditional sauna is a wood-lined room heated to roughly 80 to 100°C with low humidity. Sit in it and your skin temperature climbs quickly, blood vessels near the skin widen, and your heart speeds up to push more blood towards the surface so you can lose heat through sweat. A large review of sauna research describes heart rates of around 100 to 150 beats per minute during a session, similar to gentle or moderate exercise, and an average of about 0.5 kg of sweat lost.

That matters if you go in straight after training. You are adding heat to a body that is already warm, sweaty and possibly low on fluid. For most healthy adults that is fine in sensible doses, but the sauna is still a load on your body, even if it feels like rest.

What does the research show about sauna after exercise?

Less than social media suggests, but it is not nothing.

• Heat adaptation. The most quoted study put six male competitive runners in a sauna for about 30 minutes straight after training, on roughly a dozen occasions over three weeks. Their time to exhaustion on a treadmill test improved compared with normal training, which the researchers estimated as close to a 2% faster 5K. It was a tiny study, but the likely reason, more blood plasma after repeated heat exposure, is well recognised, and a later study in trained middle-distance runners found similar improvements in fitness markers.
• Heart health links. A long-running study of more than 2,300 middle-aged Finnish men found that those who used a sauna more often had lower rates of fatal heart disease over around 20 years. That is a link, not proof, and it says nothing specific about sauna after a workout.
• Short-term recovery. The evidence here is mixed. One study in competitive swimmers found their follow-up swim test was slightly slower after a sauna than after a placebo, and they reported feeling more stressed. A small study of infrared sauna after strength training found no effect on muscle growth.
• Relaxation. This is where most people notice a difference. Many find it helps them unwind and sleep more easily, though that evidence is mostly based on how people say they feel.

What it does not do: sweating is not a meaningful way to detox, as your liver and kidneys already handle that. And any weight you lose in the sauna is water, which comes straight back when you drink.

How long and how hot should a beginner go?

Start small. For your first few sessions, 5 to 10 minutes is plenty, sitting on a lower bench. Heat rises, so the top bench is noticeably hotter.

A common approach is to work in rounds: time in the heat, then a cool shower or a few minutes sitting outside, then back in if you feel good. Over a few weeks you can build towards two or three rounds of 10 to 15 minutes. There is no prize for staying in longest. Get out straight away if you feel dizzy, sick or headachy, or your heart feels like it is racing, and stand up slowly, because a quick drop in blood pressure can leave you light-headed.

A starting point for healthy adults, not a prescription. Shorten or skip a session whenever you feel off.

Should you use the sauna after training or on rest days?

After training. This is when the heat adaptation research was done, because your core temperature is already raised. Cool down, have a drink and let your breathing settle first. After a very hard HIIT session, a long run or a race, keep it short or skip it. That is when people tend to feel faint.

On rest days. A relaxed session on a rest or easy day is a nice way to unwind without stacking heat on top of hard work. If your goal is to switch off or sleep better, this is often the more comfortable choice.

Before training. Generally not a great idea. A sauna is no substitute for a proper warm-up, and starting a session hot and slightly dehydrated makes it harder.

If you follow a hybrid plan that mixes running, strength and HIIT, look at the week as a whole. Pair the sauna with easy runs, mobility or lighter strength days, and keep it away from the evening before your hardest session. Edge builds running, strength, HIIT and mobility into one fully personalised plan, so it is easy to see where the tough days fall, and you can message a real coach if you want help deciding where heat fits in.

How much should you drink around a sauna session?

You can lose around half a litre of sweat in one session, and more straight after a sweaty workout, so fluid matters.

• Arrive well hydrated, especially after a hard session or on a warm day.
• Drink between rounds, and take a water bottle in with you if the venue allows it.
• Afterwards, drink steadily rather than downing a litre in one go.
• Skip the alcohol. Alcohol and heat can both lower your blood pressure and dull your sense of overheating, which is a risky mix.

A simple check: if you feel thirsty or headachy later, or your pee is dark, you did not drink enough.

Who should check with a GP before using a sauna?

Most healthy adults tolerate a sauna well, but heat puts real demands on your heart and blood pressure. Speak to your GP first if any of these apply:

• You have a heart condition, have had a heart attack or chest pain, or have been told you have an irregular heartbeat.
• You have high or low blood pressure, or take medication that affects your blood pressure or heart rate.
• You are pregnant. Overheating is best avoided in pregnancy, so check with your midwife or GP before using a sauna or steam room.
• You feel unwell, have a temperature or are getting over an illness. Wait until you are properly better.
• You have a history of fainting or feeling dizzy in the heat.

And whatever your health, do not use a sauna after drinking alcohol.

Sauna or steam room: which is better after a workout?

A sauna is hot and dry, usually around 80 to 100°C with low humidity. A steam room is much cooler on the thermometer, often around 40 to 50°C, but close to 100% humidity. Because sweat cannot evaporate in a steam room, it can feel just as intense, even at a lower temperature.

Most of the performance research has been done in saunas, so if heat adaptation is your goal, the sauna is the better studied option. If you simply want to relax, pick whichever you find more comfortable. The same safety rules apply to both.

What about ice baths? Cold water and heat do different jobs. Cold is mostly used to ease soreness quickly, while heat is more about relaxing and, over weeks, adapting to warm conditions. Neither is essential.

Where can you use a sauna in the UK?

More places than you might think.

• Gyms and health clubs. Many gyms include a sauna, and sometimes a steam room, in the membership.
• Leisure centres. Plenty of council-run leisure centres have a sauna or small spa area, often bookable alongside a swim.
• Community saunas. A fast-growing UK trend. Counts from within the UK sauna community suggest public sauna sites more than doubled between 2023 and 2024, from riverside and seaside cabins to saunas in parks and at lidos. Most work on booked time slots.

Wherever you go, shower first, sit on a towel, check the house rules on swimwear and session length, and stick to any posted time limit.

What is the simplest way to start?

Pick one or two sessions a week, ideally after an easier workout or on a rest day. Drink a glass of water, do one round of 5 to 10 minutes on a lower bench, cool off with a shower, drink again, and notice how you feel the next day. If that felt good, add a second round next time. If not, there is no need to push it.

Keep it in proportion. Consistent training, good sleep and decent food will always do far more for your fitness than time in the heat. The sauna is the pleasant extra, not the plan.

This article is general guidance, not medical advice. If you are new to exercise, returning from injury, pregnant, or managing a health condition, speak to your GP before starting, and see a physio for any niggle that does not settle.