Sauna Research Foundation: advancing the science of sauna and heat therapy. Research news, studies and events.
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Heat may help when movement isn't possible. In a small human study, daily local heating of an immobilized leg helped preserve the muscle, an early but encouraging lead for recovery after injury.
The boots are ready by the bed. The immobilized leg cannot follow them yet.
That forced pause reveals one of the most clinically relevant uses of heat.
In a small human study, researchers applied local heating every day to an immobilized leg. The treatment preserved mitochondrial function and attenuated muscle loss in that limb. During disuse, the immediate problem is the decline produced by inactivity, so limiting that decline can matter.
The finding needs to remain attached to its setting. This was local heating of an immobilized limb. It does not show that a whole-body sauna builds muscle in healthy people who can train.
The post-training evidence is more restrained. A meta-analysis combined 6 interventions involving 125 healthy young adults. The programmes lasted at least 4 weeks, and heat was applied after resistance exercise using different methods. The signal for extra muscle mass was modest and uncertain. There was no measurable additional gain in strength. Training carried the strength adaptation.
These 2 lines of evidence answer different questions. After ordinary resistance training, heat appears compatible with adaptation and may add a small muscle-mass signal. During immobilization, local heat may help preserve mitochondrial function and attenuate atrophy while movement is restricted.
A fracture, severe joint problem or period of convalescence can place someone in that second situation. Heat may then fit inside a supervised plan to reduce deconditioning and prepare the return to activity. The goal should remain explicit: restore safe movement, then rebuild walking and training progressively.
Whether heat is appropriate depends on the injury, cardiovascular status, medication and rehabilitation plan. That decision belongs with the treating clinician.
I would use heat as part of the bridge back to movement. Once loading becomes possible, rehabilitation and exercise provide the mechanical stimulus required for strength and function.
Older adults are often the most vulnerable in the heat. Deshayes and colleagues found that heat acclimation improved neural control of body temperature during heat stress in older adults, a promising lead worth building on.
Research by Thomas A. Deshayes (@ICMtl) and colleagues finds that heat acclimation improves the #neural control of body #temperature during heat stress in older adults 🌡️ 🧠
Read the study 👇️
buff.ly/tcYwrPC
A 12-week trial found that 40°C hot-water immersion three times a week improved vascular function about as much as moderate aerobic exercise. It's not a replacement for exercise, but it's a promising option for people who find exercise hard.
Hot water immersion improved vascular function as effectively as zone 2 aerobic exercise.
Participants completed three weekly sessions of either 40-minutes in 104°F (40°C) water or 40 minutes of moderate-intensity aerobic exercise. After 12 weeks, both groups showed comparable improvements in flow-mediated dilation (a measure of how effectively blood vessels widen in response to increased blood flow).
Research supports similar benefits for other passive heat modalities such as sauna. Neither is a replacement for exercise, but their ability to produce similar improvements in endothelial function is remarkable.
As heat waves become more common, this J Appl Physiol spotlight asks whether regular passive heating could help prepare the people most at risk. A thoughtful idea that deserves careful trials.
Teams from @ICMtl and @i-med.ac.at worked together to put together this great spotlight piece, Passive #heat #therapy: a promising preventive measure for people at risk of adverse health outcomes during heat extremes (Patrick Rodrigues et al.):
ow.ly/Y9k150ZGgxs
Thank you NPR for the coverage of the 1st Intl Heat Therapy Research Symposium npr.org/2026/10/12/nx-s1-597…
A balanced take on infrared versus traditional sauna. Infrared can deliver real heat stress, but most of the long-term evidence comes from Finnish-style sauna, so whether the benefits match is still an open research question.
Infrared vs. traditional sauna. Are the benefits really the same?
I get asked this question constantly! My take is that infrared saunas can absolutely produce meaningful heat stress, but they're not necessarily equivalent to traditional Finnish saunas.
Traditional saunas heat the surrounding air, typically around 175-195°F, whereas infrared saunas use radiant heat and generally operate at lower temperatures (110-150°F).
The important question is how much thermal stress you're actually generating.
I personally prefer traditional Finnish saunas. Most of the compelling long-term evidence linking sauna use to lower cardiovascular mortality and dementia risk comes from traditional Finnish sauna studies.
But if infrared is what you have access to, I wouldn't dismiss it!
My recommendation would be to fully preheat the sauna and recognize that you may need a longer exposure to generate comparable heat stress. Importantly, there's no established temperature-duration formula that makes infrared equivalent to traditional sauna.
Infrared saunas can deliver substantial heat stress, but whether they produce the same long-term health benefits as traditional saunas remains an open question.
On the other hand, there is a growing body of evidence that IR saunas, as part of a clinical hyperthermia protocol, can have substantial antidepressant effects in people with major depressive disorder!
At the end of the day, it seems deliberate heat exposure (up to a point) is broadly beneficial however we get there.
A randomized UCSF trial is testing whether adding at-home sauna blanket sessions to digital CBT-I helps adults who have trouble falling asleep. It's still recruiting, and we look forward to what it finds.
A useful head-to-head from the University of Oregon: in 20 healthy adults, hot-water immersion raised core temperature more than traditional or infrared sauna and drew stronger cardiovascular and immune responses. The heat dose seems to matter more than the method.
Comparison of Thermoregulatory, Cardiovascular, and Immune Responses to Different Passive Heat Therapy Modalities
Authors: Jessica K. Atencio, Emma L. Reed, Karen Wiedenfeld Needham, Kathryn M. Lucernoni, Lindan N. Comrada, John R. Halliwill, Christopher T. Minson
Heat therapy is essentially controlled physiological stress. Raise body temperature sufficiently and the body responds by increasing skin blood flow, heart rate and cardiac output while reducing vascular resistance—responses that share important characteristics with moderate aerobic exercise. Repeated exposure to passive heat has been studied for potential cardiovascular, metabolic and anti-inflammatory benefits.
In this University of Oregon study, 20 healthy adults underwent hot-water immersion, traditional sauna and far-infrared sauna. Hot-water immersion produced the strongest thermal response. Core temperature increased about 1.1°C, compared with 0.4°C during traditional sauna and essentially no increase during the infrared-sauna protocol.
That greater thermal load translated into a stronger cardiovascular response. Hot-water immersion increased cardiac output by about 3.7 L/min and produced the largest reductions in blood pressure and systemic vascular resistance. It was also the only treatment to significantly increase IL-6 immediately afterward, followed by increases in natural killer cells at 24 hours and cytotoxic CD8+ T cells at 24 and 48 hours.
Water is particularly effective because its thermal conductivity is approximately 24 times greater than that of air, allowing heat to transfer into the body much more efficiently. During immersion, the submerged body also loses much of its ability to cool itself through sweat evaporation. The result is a much stronger increase in core temperature even though sauna air is considerably hotter.
Another important component of thermal therapy is the cellular heat-stress response. Sufficient heat exposure can increase heat-shock proteins—molecular chaperones that help protect proteins, maintain protein folding and improve cellular resistance to stress. This mechanism is part of the broader scientific rationale for repeated heat therapy, although heat-shock proteins were not measured in this particular experiment.
The important message is that thermal therapy is not simply about feeling hot. The biological stimulus comes from creating enough controlled thermal stress to activate cardiovascular, immune and cellular stress-response systems.
In this head-to-head experiment, hot-water immersion delivered the strongest physiological heat stimulus of the three methods tested.
A randomized trial, not just an association. Adding sauna after training improved fitness and blood pressure more than exercise alone in at-risk adults, and it's worth replicating in larger groups.
Adding sauna after training improved VO2max and systolic blood pressure compared with exercise alone in one randomized trial.
Researchers in Finland followed 47 sedentary adults with at least one cardiovascular risk factor. Their average age was 49. For 8 weeks, participants completed 3 exercise sessions per week. One group stopped after exercise; the other added 15 minutes of sauna after each session.
The comparison gives us a useful measure of the additional effect. The exercise-plus-sauna group gained 2.7 mL/kg/min more VO2max than the exercise-only group. Its systolic blood pressure fell by an additional 8 mmHg, and total cholesterol also decreased.
Those results fit the physiology. Heat sends more blood toward the skin. The increased flow creates shear stress along the vessel wall, which stimulates the endothelium. Exercise uses that same vascular pathway while also loading muscles, bones, balance, coordination and aerobic capacity.
In daily life, exercise supplies the broad training stimulus, and heat may then extend part of the haemodynamic work. Before training, heat can cause dehydration and fatigue, which may lower the quality of the session.
This trial also has clear boundaries. It included 47 people and measured changes over 8 weeks. It cannot tell us what happens over 20 years, and it does not turn sauna into a treatment for every person with high blood pressure.
The observational Finnish data require the same restraint. Frequent sauna use was associated with lower cardiovascular mortality over more than 20 years, but those cohorts do not establish causality.
In practice, complete the exercise first, then consider heat if it suits your health and schedule. Sauna never replaces physical activity, does not count toward the 150 weekly minutes, and does not remove the need to treat hypertension. Anyone with heart disease should discuss regular heat exposure with a doctor.
Proud to have been part of the first heat therapy research symposium in Oslo. The goal is rigorous science on sauna and heat exposure, not hype. Next up is agreeing on what the evidence shows and where the gaps are.
Sauna science is growing up. Our research partner Ashley Mason of UCSF helped organize the first heat therapy research symposium.
Her goal: "not something fringy, or woo-woo."
Next: researchers aim to agree on what we know, and what we don't. Via NPR:
npr.org/2026/10/12/nx-s1-597…
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🚨 David Sacks on Elon Musk:
"Elon Musk still works incredibly hard. I visited him recently, I left around midnight and he was still working. I think he must have gone till 2am. So I don't know anybody who works as hard as him. He's really in the technical details of it."
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we are so back it’s not even funny
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Chemotherapy can speed up cancer spread, Chinese study finds | Victoria Bela, South China Morning Post
Common treatment can wake up dormant cancer cells, causing the disease to spread from original sites to other organs, team discovers
A team of Chinese scientists has found that the spread of cancer from original tumour sites to distant organs can be caused by chemotherapy triggering the awakening of dormant cancer cells.
Their findings shed light on why breast cancer patients can experience cancer metastasis in organs like the lungs despite successful treatment of their primary tumours.
The team also found that the use of specific drugs in combination with chemotherapy could be used to inhibit this process in mice, and a clinical trial is already under way in breast cancer patients.
“We demonstrate that chemotherapeutic drugs, including doxorubicin and cisplatin, enhance proliferation and lung metastasis of dormant breast cancer cells,” the team wrote in a paper published in the peer-reviewed journal Cancer Cell on July 3.
“This study provides direct evidence of dormancy awakening and reveals a mechanism underlying [the] detrimental effect of chemotherapy on metastasis, highlighting potential strategies to improve cancer treatment.”
Researchers in the United States previously found that high doses of radiation therapy to treat cancer could paradoxically lead to the growth of metastatic tumours.
Many patients who undergo chemotherapy to treat primary tumours, the original tumour site in the body where cancer cells first start to develop, can have cancer relapses in other organs even after complete primary tumour regression.
This has led to research into whether chemotherapy can have a similar paradoxical effect, in which it both treats primary tumours and triggers cancer metastasis.
“It is postulated that the reactivation, or awakening, of dormant disseminated tumour cells (DTCs) in distant organs results in metastatic relapse after the asymptomatic period,” the team said.
Studies have shown that disseminated cancer cells, which travel from primary tumours to sites in the body, can be found even during the early stages of primary cancer formation, according to a news release by the Chinese Academy of Sciences (CAS).
These cells can stay in a dormant state for years, during which they do not grow and multiply, allowing them to evade chemotherapy.
Researchers have previously identified molecular mechanisms that regulate metastatic relapse and disseminated cancer cell dormancy. However, it has not been clear whether metastasis results from the reactivation of dormant cells or the growth of rare, non-dormant disseminated cells.
“Understanding the exogenous causes of DTC awakening will help disease management of cancer survivors, offering opportunities to prevent and interrupt metastatic relapse after initial therapies,” the researchers said in their paper.
To study this, the team led by Hu Guohong, a professor at CAS’ Shanghai Institute of Nutrition and Health, along with researchers from Fudan University and Qilu Hospital of Shandong University, developed a cancer cell dormancy tracing approach.
The team confirmed that chemotherapy-induced reactivation of dormant cells from breast cancer could lead to metastatic relapse in the lungs of mice.
Their findings demonstrated that the “awakening of dormant DTCs, but not accumulation of pre-existing proliferative DTCs, is responsible for metastases induced by chemotherapy”.
Chemotherapy induces senescence – an accelerated state of ageing in which cells stop multiplying and release inflammation-causing chemicals – in specialised connective tissue called fibroblasts.
The team found that senescent fibroblasts release proteins that cause immune cells called neutrophils to form weblike formations, called neutrophil extracellular traps, which change the environment in the lung into one that helps dormant cancer cells restart their growth.
The remodelling of the extracellular matrix, a complex network of molecules that support and surround cells, also degrades tumour-suppressing factors.
“We explored if chemotherapy-induced senescent fibroblasts could be a therapeutic target to improve the effect of chemotherapy on metastasis inhibition,” the team said.
The researchers discovered that combining senolytic drugs, which eliminate senescent cells, with the chemotherapy drug doxorubicin reduced senescent fibroblasts in the lungs of mice.
“Since the senolytics have shown acceptable safety profiles and benefits in clinics, this could be a promising strategy and warrant further clinical investigation,” they said.
The team said that, based on these study results, a phase II clinical trial was under way to explore the safety of combining the senolytic drugs dasatinib and quercetin with chemotherapy to treat triple-negative breast cancer.
Read more:
archive.is/bQdIz
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This was a pretty great follow up from Scottie on his presser early in the week.
