Heat & Sauna - Heat & performance
Sauna after exercise: adaptation vs extra fatigue
Last updated 29 September 2026. How we write this .
Regular sauna after training expanded blood volume and improved endurance in small trials, but one hot session can leave you slower the next day. Reviews rate the overall evidence as low certainty.
Start here Regular sauna after training expanded blood volume and improved endurance in small trials, but one hot session can leave you slower the next day. Reviews rate the overall evidence as low certainty.
By the end, you will understand What does a sauna do to your body after exercise? Can a sauna after training improve endurance? Will a sauna help me recover for tomorrow? Key words used in this lesson Placebo An inactive comparison given so that the effect of expectation can be separated from the effect of the intervention itself. Without one, improvement over time cannot be attributed to the treatment. Meta-analysis A statistical method for combining the results of multiple studies into a single estimate. More reliable than any one study, but bounded by the quality of what went into it. Systematic review A review that searches for all the evidence on a question using a pre-declared method, rather than selecting studies that suit an argument. The method is what distinguishes it from an ordinary review article. Full plain-English glossary
Where this information comes from Claim-cited evidence. Central research claims on this lesson are linked to specific studies or official guidance.
This lesson links the specific studies and guidance used for its central claims.
Our standard: expert or athlete opinion may illustrate a viewpoint, but it is never treated as proof. Read the editorial policy .
Report an error or outdated claim .
Sitting in a sauna after training can help or hinder, depending on what you want from it. Over several weeks, small trials show it can expand the volume of your blood and improve endurance, especially in hot conditions. In the short term it adds heat strain and fluid loss on top of a hard session, and in at least one trial it left athletes slower the next morning.
So the honest answer to "should I sauna after the gym?" depends on your goal and your timing. If you are building fitness over weeks, the heat may act as an extra training stimulus. If you need to perform hard tomorrow, it may cost you.
What does a sauna do to your body after exercise?
When you stop exercising, your body is already hot and has already lost fluid as sweat. A sauna keeps your core temperature up at the point it would normally be falling. To shed that heat, your heart sends more blood to the skin, your heart rate stays high and you keep sweating. The blood vessels in your legs are also still widened after exercise. Without working muscles squeezing blood back towards the heart, blood pressure can drop, which is why some people feel light-headed when they stand up after a post-workout sauna.
Repeated over days, that stress prompts the body to adapt. The best documented change is a rise in plasma volume, the watery part of the blood. More plasma lets the heart fill more fully with each beat and leaves more fluid available for sweating. Athletes get the same adaptation from training in hot weather, which is why researchers describe post-exercise sauna as a form of passive heat acclimation.
Can a sauna after training improve endurance?
The study most often quoted comes from the University of Otago in New Zealand. In 2007 Guy Scoon and colleagues had six male distance runners add a humid sauna at about 90°C, for around 30 minutes after training, on roughly 13 occasions over three weeks. They compared this with three weeks of normal training. After the sauna block the runners lasted 32% longer in a treadmill run to exhaustion, which the authors calculated was equal to about a 1.9% improvement in a race-style time trial. Plasma volume rose by 7.1%, and the runners whose blood volume rose most tended to improve most.
In 2015 Jamie Stanley and colleagues in Australia followed seven well-trained male cyclists who added a 30-minute sauna at 87°C after normal training for 10 days. Plasma volume peaked after just four sessions, at about 17.8% above baseline, and heart rate on waking fell by around 10%. This study measured blood and heart rate, not race performance.
A 2021 University of Birmingham trial led by Nathalie Kirby was larger and included women. Twenty middle-distance runners, 13 of them female, either trained normally or added a sauna after training about three times a week for three weeks. The sauna group improved its VO2max, the most oxygen the body can use during an all-out effort, by more than the control group. In a 30-minute test run in 40°C heat, the sauna group's heart rate came down by 11 beats a minute and its peak core temperature by 0.2°C, more than in the runners who trained normally.
Will a sauna help me recover for tomorrow?
This is where the picture changes. In a 2020 crossover trial, Sabrina Skorski and colleagues tested 20 competitive swimmers and triathletes after a hard training session. On one occasion the athletes had three 8-minute sauna rounds at 80 to 85°C. On the other they rested while applying a massage oil that served as a placebo. The next morning, after the sauna, they swam a set of four 50-metre sprints 1.69 seconds slower in total than before training. After the placebo they were 0.66 seconds faster. Fifteen of the 20 athletes got slower after the sauna, and they reported feeling more stressed. The researchers told coaches and athletes to be careful with post-exercise sauna when hard training or competition is planned for the next day.
Other recovery studies point in different directions. A 2025 systematic review led by Essi Ahokas of the University of Jyväskylä in Finland found nine trials of short-term recovery after heat. Four showed no effect, four a benefit and one harm. The results shifted with the type of heat, the sport and how recovery was measured, so a single session's effect on how you feel or perform tomorrow is hard to predict.
What do the reviews say overall?
Two recent reviews pulled the trials together. Ahokas and colleagues included 14 trials with 194 participants in total. The longer training studies suggested post-exercise heat may improve running performance, at least in hot conditions, but repeated heat made no difference to cycling performance or VO2max. They rated the evidence as low to moderate quality and said firm conclusions were not possible.
A 2025 meta-analysis by Thomas Solomon and Matthew Laye pooled 10 studies with 199 participants, 156 of them men, aged 20 to 32. The pooled estimate for performance in hot conditions was a 4% improvement, but the plausible range ran from a 6% decline to a 15% gain, and the authors judged the effect trivial. Effects on performance in normal temperatures were also trivial. They graded certainty as low to very low, because the studies were small, carried a high risk of bias and may have been skewed by negative results that were never published.
That is the genuine uncertainty. The rise in blood volume after repeated post-exercise heat is a consistent finding. Whether it turns into faster race times for most people has not been shown, and almost all the data come from young, fit men.
Is it safe to use a sauna straight after a workout?
Sauna bathing is well tolerated by most healthy adults, according to a 2001 review in the American Journal of Medicine by Hannuksela and Ellahham, written from the University of Oulu in Finland. After exercise, the extra risks are fluid loss and a fall in blood pressure, so the usual cautions apply with more force.
Alcohol. Hannuksela and Ellahham found that drinking alcohol during sauna bathing raises the risk of low blood pressure, abnormal heart rhythms and sudden death, and should be avoided. Heart conditions. The same review lists unstable angina, a recent heart attack and severe aortic stenosis (a narrowed heart valve) as reasons not to use a sauna. If you have any heart condition, ask your GP or cardiologist first. Heat exhaustion. The NHS lists dizziness, headache, nausea, cramps, heavy sweating and intense thirst as signs. Get out, cool down and drink fluids. Contact NHS 111 if you are struggling to manage it. Heatstroke. Call 999 if someone is still unwell after 30 minutes of cooling, or has hot skin that is not sweating, fast breathing, confusion, a fit or loss of consciousness. The NHS treats heatstroke as a medical emergency. This lesson explains research on sauna use after exercise for general education. It is not medical or training advice, so talk to your GP first if you have a heart condition or other health problem.
Related in this classroom Related in other classrooms The studies behind this page Effect of post-exercise sauna bathing on the endurance performance of competitive male runners - Journal of Science and Medicine in Sport, 2007Effect of sauna-based heat acclimation on plasma volume and heart rate variability - European Journal of Applied Physiology, 2015Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners - European Journal of Applied Physiology, 2021Effects of postexercise sauna bathing on recovery of swim performance - International Journal of Sports Physiology and Performance, 2020Effects of post-exercise heat exposure on acute recovery and training-induced performance adaptations: a systematic review - Sports Medicine - Open, 2025The effect of post-exercise heat exposure (passive heat acclimation) on endurance exercise performance: a systematic review and meta-analysis - BMC Sports Science, Medicine and Rehabilitation, 2025Benefits and risks of sauna bathing - American Journal of Medicine, 2001Heat exhaustion and heatstroke - NHSSources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.