Why Sauna — Lessons From latest research in Cold & Heat
Hi Thermalist reader,
When I first started my scientific career, I was fascinated by one question:
How can we use natural temperature extremes — cold and heat — to improve human health, without medication or complicated interventions?
That question led me to conduct some of the first real-world controlled studies on contrast therapy — combining cold water immersion and sauna — to measure how these ancient practices affect metabolism, cardiovascular function, and recovery.
I didn’t just look at the immediate effects. I studied what happens after you step out of the water or the heat — how your body’s systems continue to adapt for hours, even days.
The findings were clear:
Cold and heat trigger different, complementary adaptations.
Sauna, in particular, has been underestimated. It’s not just relaxation — it’s a powerful form of passive cardiovascular training with benefits as measurable as exercise.
Today, I want to share with you the latest research that supports what I’ve seen both in the lab and in real-life practice — and show you how to use sauna in a way that transforms not just your recovery, but your long-term health.
Sauna Is Physiological Training
Sauna use triggers a cascade of physiological responses:
Your heart rate rises to the level of moderate exercise.
Blood vessels expand, increasing circulation.
Nitric oxide is released, relaxing arteries and improving blood flow.
Heat shock proteins are produced, which protect and repair your cells.
These changes don’t just feel good — they create long-term improvements in cardiovascular function, metabolic health, and resilience.
The Latest Science on Sauna
Here’s what the newest research is telling us:
1. Finnish Sauna & Long-Term Health Outcomes
Laukkanen et al., 2024 — PubMed 38577299
Finnish population studies — among the best data we have — show that regular sauna use (4–7 sessions/week) is linked with:
Lower risk of cardiovascular disease, stroke, and dementia
Lower blood pressure over both the short and long term
Greater benefits with more frequent sessions (dose-response relationship)
This mirrors what I’ve seen in my own research: the more regularly you expose yourself to heat, the stronger the protective effect.
2. Sauna & Cardiovascular Function — Meta-Analysis
Li & Jiang, 2020 — PubMed 32814462
Pooling data from multiple studies, this analysis found sauna sessions:
Improved heart pumping efficiency (ejection fraction) by ~3% in people with heart conditions
Increased walking endurance by ~48 meters in the 6-minute walk test
Lowered systolic and diastolic blood pressure (~5/4 mmHg)
Made arteries more elastic, improving vascular health
This is why I call sauna “cardio without the running shoes.”
3. Infrared Sauna & Post-Exercise Recovery
Mero et al., 2015 — PubMed 26180741
Using far-infrared sauna after intense training:
Cleared blood lactate faster, reducing muscle fatigue
Restored neuromuscular performance more quickly
Likely improved recovery through increased peripheral blood flow
In my research on cold and heat, I’ve seen the same — targeted heat exposure can accelerate recovery between training sessions or even between stressful days.
Cold + Heat = Complete Adaptation
From my own studies, I’ve learned that cold and heat activate different parts of the nervous system — and both are needed for full resilience.
Cold activates the sympathetic “gas pedal,” building stress tolerance.
Heat activates the parasympathetic “brake,” teaching your body to release stress and recover deeply.
When you combine them with the right sequence and timing, you create an adaptation system that works on every level — heart, metabolism, mood, and immune function.
Learn the Thermalist® Method at Home
If you want to learn how to use sauna + cold + breathwork at home — my 3.5-hour Thermalist® at Home course will guide you step-by-step.
You’ll learn:
How to combine cold and heat for maximum benefit
Timing, temperature, and duration protocols for your specific goals
Safety guidelines for different health profiles
How to design a personalized Thermalist® Method you can do at home
👉 Start here: Thermalist® at Home — Get Started
To your adaptation,
Dr. Susanna Søberg
Founder of Søberg Institute & Thermalist®