Sauna After Training: Benefits, Risks and How to Do It Safely
For many gym members, a few minutes in the sauna is the natural end to a session. It feels relaxing, it is often included in the membership, and in Finland it is practically a national institution. But does sitting in the heat after training actually help recovery or performance, and are there situations where it does more harm than good? Our editorial team reviewed the evidence.
What happens to the body in a sauna
A traditional Finnish-style sauna typically operates at around 80–100 °C with low humidity, while infrared cabins run at lower air temperatures and heat the body more directly. In both, skin temperature rises quickly and core temperature follows more slowly.
The body responds by widening blood vessels in the skin to release heat. Heart rate rises, sometimes to levels similar to light or moderate exercise, and cardiac output increases. Sweating begins within minutes and can lead to substantial fluid loss during longer sessions.
Blood pressure often falls slightly during the session because of vasodilation and may fall further on standing up, which explains the light-headedness some people feel when leaving the sauna. Hormonal responses include rises in noradrenaline and growth hormone, although their practical significance for muscle growth is unclear.
After training, the body is already warm, partially dehydrated and has a raised heart rate. A sauna adds further heat stress on top of this, which is the main reason for caution and good timing.
Performance and heat adaptation
The best-known performance study is by Scoon and colleagues, who asked competitive male runners to spend around 30 minutes in a sauna after training sessions over three weeks. Endurance performance in a run-to-exhaustion test improved compared with the control period, accompanied by an increase in plasma volume.
Stanley and colleagues similarly found that repeated post-exercise sauna sessions increased plasma volume in trained cyclists. Greater plasma volume improves the body's ability to dissipate heat and maintain cardiac output, which helps endurance performance, particularly in hot conditions.
This makes post-exercise sauna a practical tool for athletes preparing for competition in warm climates who cannot train in the heat. Sports scientists sometimes call it passive heat acclimation.
Evidence for strength and power athletes is much thinner. There is no good evidence that sauna use increases muscle growth or maximal strength, despite marketing claims based on hormone changes.
Recovery, relaxation and long-term health
Many people use sauna primarily to relax. The quiet, warm environment and the drop in muscle tension after heat exposure can help with mental decompression after training, and some people report better sleep on sauna days. Controlled trials on sleep are limited, but there is little reason to doubt the subjective benefit for those who enjoy it.
Effects on muscle soreness are modest. Heat may increase blood flow and reduce perceived stiffness, but evidence that sauna speeds up actual muscle repair is weak. For delayed-onset muscle soreness, it should be considered a comfort measure rather than a treatment.
Population studies from Finland have attracted much attention. Laukkanen and colleagues followed more than 2,000 middle-aged men and found that those who used the sauna more frequently had lower rates of fatal cardiovascular disease and all-cause mortality. These are observational findings, so they cannot prove cause and effect, but they are reassuring about the safety of regular sauna use in healthy people.
A systematic review by Hussain and Cohen concluded that regular dry sauna bathing may have benefits for blood pressure, cardiovascular function and some musculoskeletal conditions, while noting limitations in study quality.
Risks and who should be cautious
For healthy adults, sauna use is generally safe. Kukkonen-Harjula and Kauppinen, reviewing health effects and risks, noted that most serious incidents involve alcohol, pre-existing heart disease or excessive duration.
| Situation | Main risk | Recommendation |
|---|---|---|
| Dehydration after training | Dizziness, fainting, cramps | Rehydrate first; keep sessions short |
| Alcohol consumption | Hypotension, arrhythmia, accidents | Avoid sauna after drinking |
| Unstable heart disease, recent heart attack | Cardiac events | Medical clearance required |
| Low blood pressure, fainting history | Collapse on standing | Stand up slowly, seek advice |
| Pregnancy | Overheating | Discuss with midwife or GP |
| Trying to conceive (men) | Temporarily reduced sperm quality | Consider limiting frequency |
Combat-sport athletes sometimes use saunas to "make weight" through rapid dehydration. This practice is associated with impaired performance, heat illness and, in extreme cases, death. The ACSM position stand on exercise and fluid replacement warns against substantial fluid deficits.
People using stimulants, diuretics or certain performance-enhancing drugs should be particularly careful, because these can impair temperature regulation or fluid balance and increase strain on the heart.
Practical guidelines for post-workout sauna
The following guidance applies to healthy adults. Anyone with a medical condition should check with their doctor first.
- Cool down and drink water before entering, especially after a sweaty session.
- Start with short sessions of 5–10 minutes and build up gradually over weeks.
- Leave immediately if you feel dizzy, nauseous or unwell.
- Stand up slowly and sit for a moment after leaving the sauna.
- Replace fluids and, after long or very sweaty sessions, some sodium.
- Never combine sauna with alcohol, and avoid using it when ill with fever.
Timing can be adjusted to your goals. If you train hard in the evening and struggle to fall asleep, try leaving at least an hour between the sauna and bedtime so that core temperature can fall.
For athletes using sauna as heat acclimation, coaches typically plan sessions over one to three weeks before competition. Because it adds physiological stress, it should be built into the training plan rather than added on top of an already heavy load.
Many people enjoy alternating heat with a cool shower or plunge. This is safe for most healthy people, but those with heart conditions should avoid extreme temperature contrasts without medical advice.
Conclusions of the editorial team
Sauna after training is safe for most healthy adults and can be a pleasant way to relax. Regular use can expand plasma volume and improve heat tolerance, supporting endurance performance.
Claims about muscle growth are not supported, and effects on soreness are modest. Dehydration, alcohol and pre-existing heart conditions are the main risks.
Rehydrate first, start with short sessions, and listen to your body.
You might also enjoy our articles on cold-water immersion after training, hydration strategies, and sleep for recovery.
References
- Scoon GS, Hopkins WG, Mayhew S, Cotter JD. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. J Sci Med Sport. 2007;10(4):259–262.
- Stanley J, Halliday A, D'Auria S, Buchheit M, Leicht AS. Effect of sauna-based heat acclimation on plasma volume and heart rate variability. Eur J Appl Physiol. 2015;115(4):785–794.
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015;175(4):542–548.
- Hussain J, Cohen M. Clinical effects of regular dry sauna bathing: a systematic review. Evid Based Complement Alternat Med. 2018;2018:1857413.
- Kukkonen-Harjula K, Kauppinen K. Health effects and risks of sauna bathing. Int J Circumpolar Health. 2006;65(3):195–205.
- Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377–390.
- Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clin Proc. 2018;93(8):1111–1121.
