Forty-five minutes of infrared heat at 65°C raised core temperature by 1.4°C
This 2026 Experimental Physiology study measured what a commercial far-infrared cabin does to 12 adults when it runs at 65°C for 45 minutes.
The paper
Far‐infrared sauna exposure at 65°C elevates core temperature
Jenkins EJ, Killick JA, Grimm SR, Davies SR, et al.. Experimental Physiology, 2026:EP094028.
See the study at a glance
- Design
- Single-group experimental study
- People
- 12 adults (6 women)
- Who they were
- Healthy adults.
- What they did
- One 45-minute session in a commercial far-infrared cabin. The room averaged 63.9°C as it warmed from 60.7 to 65.0°C, and humidity climbed from 12.4% to 23.0%.
- How long
- One 45-minute session
These numbers came out of it
+1.4°C
Rectal temperature rose from 37.3°C to 38.7°C.
153 bpm
By the end of the session heart rate averaged 153 beats a minute. It had started at 74.
1.0 kg
People lost 1.0 kg of body mass during the session. Their sweat rate came to 1.4 L an hour.
2 of 12
Two of the 12 stopped at 40 and 43 minutes because of extreme discomfort.
The researchers did this
Twelve healthy adults (six women) sat for 45 minutes in a commercial far-infrared cabin that averaged 63.9°C.Source 1 · Clinical trialFar‐infrared sauna exposure at 65°C elevates core temperatureJenkins EJ, Killick JA, Grimm SR, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ A rectal probe tracked core temperature. The researchers also measured heart rate, blood pressure, plasma volume and body mass. A sauna maker supplied the cabin, and the paper states no role for the company in the study.
Rectal temperature rose significantly from minute 20 and ended 1.4°C higher at 38.7°C.Source 1 · Clinical trialFar‐infrared sauna exposure at 65°C elevates core temperatureJenkins EJ, Killick JA, Grimm SR, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ Skin temperature had already risen 7.4°C by minute 5, and heart rate climbed from 74 to 153 beats a minute over the session.
People lost 1.0 kg of body mass, and their sweat rate worked out to 1.4 L an hour. Plasma volume (the fluid part of the blood) fell 11.6%.Source 1 · Clinical trialFar‐infrared sauna exposure at 65°C elevates core temperatureJenkins EJ, Killick JA, Grimm SR, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ Two of the 12 ended up more than 2% dehydrated. Mean arterial pressure (the average blood pressure across a heartbeat) dropped from 90 to 81 mmHg right after the session and was back to 89 mmHg after 30 minutes of recovery.
Two participants quit because of extreme discomfort.Source 1 · Clinical trialFar‐infrared sauna exposure at 65°C elevates core temperatureJenkins EJ, Killick JA, Grimm SR, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ One stopped at 40 minutes and the other at 43. At the end, an ear thermometer read 0.4°C higher than the rectal probe.
The study can't tell you these things
- It had no comparison condition, so it can't say how the same people would respond to a traditional sauna.
- Twelve people in one cabin make a small sample.
- At 65°C the session ran hotter than the 45–60°C that infrared cabins typically use.Source 2 · Systematic reviewClinical Effects of Regular Dry Sauna Bathing: A Systematic ReviewHussain J, Cohen M. Evidence-Based Complementary and Alternative Medicine, 2018.Read the paper ↗PubMed ↗
- It covered one session and didn't follow anyone's health afterward.
From our sister magazine
Sauna Monthly compares infrared cabins on price and build
We cited these sources
- 01Jenkins EJ, Killick JA, Grimm SR, Davies SR, Benson JA, Tremblay JC, et al.. Far‐infrared sauna exposure at 65°C elevates core temperature. Experimental Physiology. 2026:EP094028. doi:10.1113/ep094028 PMID 42533687
- 02Hussain J, Cohen M. Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evidence-Based Complementary and Alternative Medicine. 2018;2018:1857413. doi:10.1155/2018/1857413 PMID 29849692