A traditional sauna warmed the body more than an infrared cabin, and a hot bath warmed it most
In this 2025 American Journal of Physiology study, the same 20 young adults tried a hot bath, a traditional sauna and an infrared cabin at the settings people commonly use.
The paper
Comparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalities
Atencio JK, Reed EL, Wiedenfeld Needham K, Lucernoni KM, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025;329(1):R20-R35.
See the study at a glance
- Design
- Randomized-order crossover study
- People
- 20 adults (10 women)
- Who they were
- Healthy adults in Oregon with an average age of 24.
- What they did
- Each person did all three, at least a week apart. The hot bath lasted 45 minutes at 40.5°C. In the traditional sauna, set to 80°C, people did three 10-minute rounds with 5-minute breaks. The far-infrared cabin session ran 45 minutes while its thermostat rose from 46 to 65°C.
- How long
- Three separate sessions
These numbers came out of it
+0.0°C
Core temperature didn't move after 45 minutes in the far-infrared cabin.
+0.4°C
Three 10-minute rounds in the traditional sauna raised core temperature by 0.4°C. The hot bath pushed it up 1.1°C.
0.39 vs 0.66 kg
People sweated off 0.39 kg in the infrared cabin and 0.66 kg in the traditional sauna, and the difference wasn't statistically significant.
66°C
A calibrated probe measured the traditional sauna's air at 66°C while its factory thermostat read 78°C.
The researchers did this
Researchers in Oregon tested three common forms of heat on 20 healthy young adults, and half of them were women. Everyone did each condition once, in randomized, counterbalanced order. At least a week separated the sessions.Source 1 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗ The sessions copied common use: 45 minutes in a 40.5°C bath, three 10-minute rounds in a dry sauna set to 80°C with two ladles of water on the stones at the start of each round, and 45 minutes in a far-infrared cabin.
A calibrated probe found both saunas cooler than their thermostats said. The traditional sauna averaged 66°C and 17% humidity while its thermostat read 78°C. In the infrared cabin the probe read 45°C and the thermostat 57°C.Source 1 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗
Core temperature climbed 1.1°C in the bath and 0.4°C in the traditional sauna. It didn't move in the infrared cabin, and each pair of conditions differed significantly.Source 1 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗ Cardiac output (the blood the heart pumps each minute) rose most in the bath, where it climbed 3.7 L/min. In the traditional sauna it rose 2.3 L/min. Stroke volume (the blood pumped with each beat) barely moved there, from 70.2 to 71.2 mL, so a faster heart rate supplied the increase.
Sweat loss followed the same order, and the bath drew the most at 0.90 kg. The traditional sauna took off 0.66 kg and the infrared cabin 0.39 kg.Source 1 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗ The difference between the bath and the infrared cabin was statistically significant. Between the two saunas it wasn't (P = 0.16).
Only the hot bath moved immune markers. It raised the inflammatory messenger IL-6 by 0.386 pg/mL after heating and shifted natural killer cells and CD8+ T cells over the next two days. Neither sauna changed immune messengers (cytokines) or immune cells.Source 1 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗
The study can't tell you these things
- Each condition was tried once, so the study can't show what happens over weeks of use.
- The volunteers were healthy and young (average age 24).
- The protocols copied common use, so the three conditions delivered different heat doses.
- Its infrared result applies to a cabin whose air measured 45°C. In a separate study, a cabin run at 65°C for 45 minutes raised rectal temperature by 1.4°C.Source 2 · 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 ↗
- It tracked the body's responses and immune markers and followed no health outcomes. The researchers didn't control for where the women were in their menstrual cycles.
From our sister magazine
Sauna Monthly weighs infrared cabins against traditional saunas
We cited these sources
- 01Atencio JK, Reed EL, Wiedenfeld Needham K, Lucernoni KM, Comrada LN, Halliwill JR, et al.. Comparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalities. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2025;329(1):R20-R35. doi:10.1152/ajpregu.00012.2025 PMID 40332494
- 02Jenkins 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