Thirty minutes in a 73°C sauna room raised blood heat shock protein 72 by 48.7% on average
In this 2012 Journal of Athletic Training study, 25 young adults spent one day in a hot sauna-style chamber and another in the same chamber at room temperature. Researchers drew blood from 13 of them.
The paper
Heat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in Humans
Iguchi M, Littmann AE, Chang SH, Wester LA, et al.. Journal of Athletic Training, 2012;47(2):184-190.
See the study at a glance
- Design
- Randomized crossover study
- People
- 25 young adults (blood from 13)
- Who they were
- Healthy students at the University of Iowa with an average age of 22. Thirteen were men and 12 were women.
- What they did
- Volunteers sat for 30 minutes on the upper bench of a sauna-style chamber at 73°C and about 10% humidity. Then they moved to a lower seat about 30°C cooler for three minutes. On the control day the same chamber was held at 26.1°C.
- How long
- One heat session and one control session
These numbers came out of it
+48.7%
Heat shock protein 72 in the blood rose 48.7% on average after the sauna. People varied widely around that average (±53.9%).
38.5°C
Rectal temperature had risen 0.82°C to an average of 38.5°C by the end of the 30 minutes. It kept climbing for about 10 minutes after people came out.
131 bpm
Heart rate climbed to an average of 131 beats a minute by the end of the session.
+285%
The hormone prolactin rose 285%, and noradrenaline rose 58%.
The researchers did this
Researchers at the University of Iowa had 25 healthy young adults spend 30 minutes in a sauna-style chamber on two days in random order. The chamber ran at 73°C on one day and at 26.1°C on the other.Source 1 · Crossover trialHeat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in HumansIguchi M, Littmann AE, Chang SH, et al.. Journal of Athletic Training, 2012.Read the paper ↗PubMed ↗ The researchers tracked everyone's heart rate and blood pressure and took blood and rectal temperature from 13 of them.
Rectal temperature held steady for about 10 minutes and then rose 0.82°C to an average of 38.50°C. It kept rising for about 10 minutes after the session ended. Heart rate climbed almost in a straight line to 131 beats per minute. By the end, systolic pressure (the top number) had fallen 16 mmHg and diastolic pressure (the bottom number) 5 mmHg.
Heat shock protein 72 circulating in the blood rose 48.7% on average, though responses varied widely from person to person (±53.9%). Of the hormones the researchers measured, noradrenaline rose 58% and prolactin 285%, and adrenaline showed no significant change. The volunteers also lost 0.5 kg of body mass.
No one left early, although people rated the heat 6.8 on a 7-point scale. Men and women responded alike.
The study can't tell you these things
- Everyone had one heat session, so the study can't show what repeated saunas do to heat shock proteins.
- Blood came from only 13 people. The analysis didn't correct for shifts in plasma volume (the fluid part of the blood), and the authors argued that posture effects were negligible.
- The volunteers were healthy students around 22 years old.
- Thirty unbroken minutes at 73°C is longer than the 5 to 20 minutes a Finnish review describes as a typical round.Source 2 · ReviewCardiovascular and Other Health Benefits of Sauna Bathing: A Review of the EvidenceLaukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018.Read the paper ↗PubMed ↗
- A later pooled analysis of 51 controlled heating studies found no overall change in heat shock proteins after single or repeated sessions.Source 3 · Meta-analysisHeat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysisPrice BS, Lucas SJE, Akerman AP, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
From our sister magazine
Sauna Monthly explains heat shock proteins in five minutes
We cited these sources
- 01Iguchi M, Littmann AE, Chang SH, Wester LA, Knipper JS, Shields RK. Heat Stress and Cardiovascular, Hormonal, and Heat Shock Proteins in Humans. Journal of Athletic Training. 2012;47(2):184-190. doi:10.4085/1062-6050-47.2.184 PMID 22488284
- 02Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence. Mayo Clinic Proceedings. 2018;93(8):1111-1121. doi:10.1016/j.mayocp.2018.04.008 PMID 30077204
- 03Price BS, Lucas SJE, Akerman AP, Gilworth RE, Lucas RAI. Heat thermotherapy to improve cardiovascular function and cardiometabolic health: A systematic review and meta‐analysis. Experimental Physiology. 2025:EP092404. doi:10.1113/EP092404 PMID 41166412