Sauna and Growth Hormone: Why the Spike Doesn't Build Muscle

1. Does sauna raise growth hormone, and does it build muscle?

Sauna can raise growth hormone (GH), but the rise has not been shown to build muscle. In a 1986 study by Leppäluoto and colleagues, ten men sat in a Finnish sauna at 80 degrees Celsius for an hour twice a day for a week (seven women took part in the prolactin measurements only). Serum GH in men rose about 16-fold during the sessions, though the response shrank after the third day. Thyroid hormones and testosterone did not change significantly. That is the origin of the "sauna boosts growth hormone" line.

But a short-lived hormone peak is not the same as growth. GH in the blood after exercise or heat drops back within hours, and muscle building depends on many other signals, mainly mechanical loading from training and protein intake. No trial has shown that sitting in a sauna produces more muscle than not doing so in people who lift.

So the honest answer to "does sauna boost growth hormone?" is: yes, GH rises, no, that does not mean you will gain muscle from it.

2. How big is the growth hormone response, and under what conditions?

It depends on how hot, how long and how dehydrated you become. In a 1989 study by Kukkonen-Harjula and colleagues, eight young men sat in a Finnish sauna until they felt uncomfortable at 80 and 100 degrees Celsius dry heat, and at 80 degrees with rising humidity, where they stayed until subjective exhaustion. Growth hormone increased at 100 degrees Celsius but not significantly at 80 degrees. Prolactin and noradrenaline rose in all conditions, and cortisol fell in the dry ones.

The authors of the 1986 paper suggested that the GH and prolactin rises might be related to heat-induced dehydration rather than a deliberately beneficial signal. This suggests the response is partly a stress response. Sitting in the heat until you are quite dehydrated may raise GH, but it is also uncomfortable and carries risk.

Both studies were small, used young healthy volunteers and were done decades ago in extreme settings that differ from a typical 15 to 20 minute gym sauna visit. They tell us the hormone responds, not that regular sauna use makes any practical difference.

3. Why a growth hormone spike does not equal muscle gain

A 2012 study by West and Phillips tested this directly in lifters. Fifty-six young men followed a 12-week resistance training programme. The researchers measured their acute hormone responses to one hard leg session at the midpoint and compared them with the gains they made. There were no significant correlations between the exercise-induced rise in GH, free testosterone or IGF-1 and gains in lean mass or leg press strength. Weak links did appear: GH response with the growth of individual muscle fibres, and, oddly, cortisol (usually seen as a catabolic hormone) with lean mass gain. Neither predicted strength.

In other words, even in the situation where we most expect hormones to matter, a bigger post-workout spike did not reliably predict who grew. The same authors made a similar case in an earlier review, questioning whether acute hormone spikes after exercise are what drive muscle growth. If a hard leg workout's own GH peak does not predict gains, a sauna-induced peak is unlikely to do so either.

That does not make GH irrelevant to health. People with real hormone disorders have clear needs. The point is that deliberately chasing a temporary peak through heat is a poor way to build muscle.

4. Heat shock proteins and muscle: what is established

Heat shock proteins (HSPs) are proteins that cells make in greater amounts when stressed by heat, helping other proteins keep their shape. Raising body temperature does increase HSP production in cells and tissues, and that is well established. The leap from there to "sauna builds muscle" is where the evidence thins out. Much of the work linking heat to muscle size comes from cell culture and animal studies, or from conditions of muscle disuse such as immobilisation. No high-quality trials in healthy people have shown that adding sauna to resistance training builds more muscle than training alone.

If you see claims that sauna "activates" muscle growth pathways, ask what type of study the claim came from. If it is a rodent or cell study, it is a reasonable hypothesis, not a result you can plan a program around. Our guide to testosterone and exercise discusses a similar gap between hormone biology and training outcomes.

5. What about testosterone and other hormone claims?

Supplement and biohacking pages often bundle several hormones into one promise. The evidence is less tidy. In the 1986 one-week sauna study, testosterone did not change significantly, cortisol and ACTH fell slightly and prolactin rose in both sexes. In the 1989 study, testosterone rose in one condition only (80 degrees Celsius with humidity) and cortisol dropped in the dry conditions. Those are measurements in a few young volunteers during or just after the sauna, not evidence of a lasting hormonal benefit.

Prolactin is the hormone that moved most consistently, and it is not one most people want to be raising on purpose. The authors of the older paper suggested dehydration might be driving it. In practical terms, a sauna session leaves you with a short burst of changes in several hormones that return to normal afterwards. For the muscle-building goal, the dependable levers remain heavy training, enough protein and enough sleep.

6. What sauna is actually good for in a training plan

The best-supported use is heat adaptation. In the Scoon study of six distance runners, 3 weeks of sauna straight after runs (around 31 minutes at about 90 degrees Celsius, about 13 sessions) increased plasma volume and run time to exhaustion compared with a control period. It was a small trial in men, but it matches the expected effect of heat acclimation, which our heat acclimatisation guide describes.

For wider health, a large Finnish cohort of 2,315 men found that those using a sauna four to seven times a week had lower risks of fatal heart disease and death over about 20 years than those using it once a week. It is observational, so it shows association, not cause.

A reasonable approach if you enjoy it:

• Two to four sessions a week, 10 to 20 minutes, starting short.
• Leave it on rest days or at least a gap after lifting; do not replace a meal or water with it.
• Drink water before and after, especially in India's heat.
• Do not use it as a substitute for protein, sleep or progressive training.

7. Safety and who should avoid it

Sauna raises heart rate substantially. In the 1989 study mentioned above, heart rate rose around 60 to 90 percent in the dry conditions. People with heart disease, low blood pressure, kidney problems or who are pregnant should ask a doctor before using a sauna. Do not use it after alcohol, or when dehydrated or ill.

Very frequent, prolonged heat can also affect reproductive hormones. In the 1986 study, five of seven women developed transient amenorrhoea after a week of twice-daily hour-long sessions, which is far beyond normal use. For men trying to conceive, repeated high heat is generally advised against, so speak to a doctor if this applies to you. Leave the sauna at once if you feel dizzy, faint or have chest discomfort.

8. Frequently Asked Questions

Q1: Does sauna increase growth hormone?

A1: Yes, in some studies. One trial found male GH levels rose about 16-fold during two one-hour sessions a day at 80 degrees Celsius over a week, though the response faded after a few days. The effect is temporary and the studies were small.

Q2: Will sauna help me build muscle?

A2: There is no good evidence that it does. Muscle growth comes mainly from progressive resistance training, enough protein and enough calories. Sauna is better thought of as a heat adaptation and relaxation tool.

Q3: How long should I stay in the sauna?

A3: Many people start with 10 minutes and build to 15 to 20. Research protocols have run up to an hour, but longer is not necessarily better. Get out if you feel unwell, and drink water afterwards.

Q4: Is sauna safe every day?

A4: For healthy adults, daily use is common in Finland and was linked to lower cardiovascular risk in observational data. If you have heart or blood pressure issues, are pregnant, or take medicines that affect blood pressure, check with a doctor first.