New research says 100°C saunas might do more than help you unwind.
We all know saunas feel incredible. The deep sweat, the sense of calm, the ritual of it all—it’s the ultimate reset. But what if those relaxing sessions were also helping your body get stronger?
According to a new study, they just might be.
A group of researchers looked at what happens when healthy young people sat in 100°C saunas a few times a week. After 12 sessions, participants saw measurable improvements in muscle mass, bone density, and overall body composition—without changing their diets or adding workouts.
Let’s break it down.
Sauna Sessions Can Support Muscle Growth
In the study, participants used a sauna heated to 100°C (212°F) three times a week for four weeks. That’s hotter than most home saunas—but well within the range of high-performance models like our Superior Hydra.
By the end of the four weeks, researchers found something surprising:
The sauna group showed a 1.07% increase in muscle mass in the right leg.
That might seem like a small number, but considering they did zero additional exercise, it’s impressive.
What’s going on here?
It’s all thanks to something called heat shock proteins (HSPs). When your body is exposed to intense heat, it activates these special proteins, which help:
- Rebuild and protect muscle tissue
- Prevent muscle breakdown
- Enhance recovery after physical or metabolic stress
So while you’re sitting back and sweating it out, your body is doing serious behind-the-scenes work.
Want more on post-workout recovery? Check out our blog on how saunas support active lifestyles.
The Surprising Link Between Sauna Use and Bone Health
Muscle growth wasn’t the only thing researchers noticed.
The same study revealed that participants also experienced a boost in bone mineral density (BMD) and bone mineral content (BMC) in their left leg:
- BMD increased by 7.7%
- BMC increased by 6.17%
To put that into context: many supplements and lifestyle programs aim for a 3–5% yearly improvement. These gains happened in just four weeks.
How does heat improve bone strength?
It circles back to heat shock proteins again—particularly HSP70, which supports:
- The formation of new bone tissue
- Activation of bone-building cells (osteoblasts)
- Alkaline phosphatase activity (important for bone mineralization)
Combined with the increased circulation and oxygenation that comes with a deep sauna sweat, you’ve got a formula for stronger bones—no dumbbells required.
The Science of Stress: Why Heat Works
At first glance, it may seem like magic. But what’s really happening is a biological process called hormesis.
Hormesis is the idea that short bursts of stress—whether it’s from heat, cold, or exercise—make your body more resilient over time. Sauna heat pushes your system just enough to trigger a beneficial response.
Here’s how your body adapts:
- Increased circulation to muscles and joints
- Boosted cellular repair through HSP activity
- Enhanced metabolic function and endurance
- Stimulated growth factors for muscle and bone
- Support for immune and hormonal balance
In other words: it’s not just about relaxation. It’s about resilience.
Curious about the science-backed benefits of a sauna? Read more here.
Who Can Benefit from High-Heat Sauna Use?
This particular study focused on young, healthy men—but the benefits of sauna use extend far beyond that group.
Here’s who might benefit most:
Athletes & Fitness Enthusiasts
Looking for faster recovery? Sauna sessions can help reduce soreness and improve post-exercise gains.
Aging Adults
Bone and muscle loss are common with age. Regular sauna use may help slow this decline and support healthy aging.
Weekend Warriors
Even if you’re not hitting the gym every day, sauna use mimics many of the benefits of exercise by boosting circulation and activating muscle-protective proteins.
Wellness Seekers
Sauna sessions offer a structured way to unwind while improving your body’s baseline strength, balance, and energy.
How Hot Is Too Hot?
The 100°C benchmark used in the study is on the high end, even for Nordic-style sauna lovers. But if you’re using one of our premium outdoor models, like the Saunum Terrace or Round Cube, those temperatures are totally achievable and safe.
Don’t worry, you don’t need to hit 100°C right away. The key is consistency.
Pro tips:
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Start with 10–15 minutes at a comfortable heat
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Gradually increase session time or temperature as your body adapts
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Always hydrate well before and after
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If you have underlying health conditions, check with your doctor first
Bringing the Benefits Home
We’ve long known that saunas help you unwind. But this new research tells a deeper story—one where heat doesn’t just relax, it rebuilds.
If you’ve been thinking about adding a sauna to your property, consider this your sign.
It isn’t just a rainy-day luxury—it’s a wellness investment that can support your body from the inside out. From increased muscle and bone strength to enhanced recovery and deeper relaxation, the benefits keep stacking up.
So whether you’re investing in recovery, longevity, or just a better way to start your morning at the cottage, your sauna sessions might be doing more for your body than you think.
Ready to turn up the heat?
