Articles
Gaining Attention From a Preventive Medicine Perspective! The Evolution of 'Sa-Watch,' a Device That Visualizes the 'Totonou' State
For sauna enthusiasts, achieving the state of 'totonou' is the pinnacle of experiences. But it's a deeply personal sensation, and many sauna beginners are left wondering what it actually feels like. Now, a new movement is underway to visualize the 'totonou' state using objective data.
Enter the Sa-Watch, a dedicated sauna wearable device. It measures your body surface temperature and heart rate variability to provide a comprehensive assessment of your body's state.
We had the chance to speak with Dr. Yasutaka Kato, a physician and the CEO of 100plus Inc., the creators of 'Sa-Watch,' to learn more about its features and the amazing health benefits of saunas.
PROFILE
Yasutaka Kato
Project Assistant Professor at Keio University School of Medicine and Representative Director of the Japan Sauna Society. A native of Tomioka City, Gunma Prefecture. After graduating from Hokkaido University's School of Medicine, he earned his Ph.D. in medicine (specializing in pathology) from the university's graduate school, with his research focusing on brain tumors. After working as a Project Assistant Professor at Hokkaido University School of Medicine, he traveled to the U.S. and conducted pancreatic cancer research at the cancer center of a Harvard Medical School-affiliated hospital. Upon returning to Japan, he worked at several hospitals, including the Center for Cancer Genomics and Precision Medicine at Keio University School of Medicine and Hokuto Hospital. He specializes in cancer genomics (cancer gene analysis) and the development of early cancer detection technologies. After witnessing the accelerating rise in medical costs, he became a staunch advocate for preventive medicine, realizing that the best way for people to live healthy, happy lives is through 'prevention' via healthy habits. His second area of expertise involves scientifically analyzing global health practices, including saunas. He co-founded the 'Japan Sauna Society' with fellow physicians and sauna enthusiasts to scientifically study and share information about saunas, and he currently serves as its representative director. His best-selling book is titled 'The Sauna Textbook Taught by Doctors' (Diamond Publishing). He has been featured in numerous media outlets, including Fuji TV's 'Honma dekka!? TV' and the magazine 'Bungeishunju'.
Why Do Saunas Need a Wearable Device?
In recent years, saunas have been gaining traction from a preventive medicine perspective. In Finland, epidemiological research spanning 50 years has recognized their effect in reducing disease risk. Beyond that, Finns cherish saunas as places for relaxation and social gatherings, not just for preventing illness.
"Most people are interested in preventive medicine, but they find it difficult to take action. If you tell someone who doesn't exercise regularly to work out three times a week for their health, very few will stick with it.
That led me to wonder if there was a way to drive behavioral change based on positive feelings like enjoyment or pleasure, rather than forcing people to do something they dislike. That’s how I landed on saunas."
However, the challenge is that the 'right' way to take a sauna varies greatly from person to person, depending on factors like optimal temperature, session duration, and even how they're feeling that day. This led to the idea that a wearable device was needed to accurately track each individual's condition.
With this goal in mind, the first-generation 'Sa-Watch' was released in 2023 as part of Gakken's "Otona no Kagaku" (Science for Adults) series. Now, the second iteration has evolved into the even more powerful 'Sa-Watch SHOWDOWN 1.'
Engineered to Endure the Extreme Heat of a Sauna
The inside of a sauna is a unique environment, and an incredibly harsh one for electronic devices.
You have intense heat, high humidity, sweat, and finally, a plunge into a cold water bath. The device needs to be not only waterproof but also capable of withstanding rapid temperature shifts. So how did they solve this challenge?
"Typical smartwatches aren't designed for sauna use, so we switched to components that could withstand the conditions.
The biggest challenge was steam-proofing. Standard waterproofing can't block steam penetration, and the alternating hot and cold plunges cause internal condensation. We had to completely rethink the design from the ground up to address that."
Furthermore, they conserve power by stripping away features unnecessary in a sauna, like email notifications. This allows for both stable performance and a long battery life.
A Proprietary Algorithm to Visualize the 'Totonou' State
The 'Sa-Watch's' standout feature is its ability to quantify 'totonou'—the blissful state that is the pinnacle of the sauna experience. 'Totonou' describes the profound relaxation that occurs when the body's parasympathetic nervous system kicks into high gear, triggered by the intense temperature shifts from the hot sauna to a cold plunge, a sensation rarely encountered in everyday life.
The thinking behind this is that by visualizing an individual’s physical condition through objective data like heart rate and heart rate variability (HRV), users can accurately monitor their own state, empowering anyone to achieve their perfect sauna session.
"The 'Sa-Watch' measures heart rate, body surface temperature, and heart rate variability (HRV). HRV is the most critical element here. It precisely captures HRV changes throughout the entire sauna cycle: from the sympathetic nervous system activation in the sauna's heat, through the sharp temperature drop in the cold plunge, and finally to the switch toward parasympathetic dominance during the open-air cool-down.
By analyzing this with our proprietary algorithm, we are now able to objectively evaluate how relaxed the user is—in other words, whether they have entered the famed 'totonou' state."
The system is designed to provide even more granular data through the companion app, 'Sa no Kuni'.
"Beyond just quantifying 'totonou,' you can also view your heart rate on a graph. In the app, we provide a 'Safety Score' and a 'Heat Intensity Score' to indicate how much your body is heating up.
Many people have the misconception that the more you push yourself in a sauna, the better, but excessive strain can actually be counterproductive. To ensure people can enjoy saunas properly, we've made it possible for them to check their heart rate as a guide."
When it comes to data logging, the app leverages your smartphone’s GPS to do more than just find nearby saunas. It also tracks which facilities you visit and precisely how long you stay. For avid sauna-goers, or 'saunners,' it's a thoughtfully designed feature that anticipates their every need.
Another noteworthy feature, which allows for a multi-faceted analysis of the sauna's effects, is the ability to track your sleep.
"We've introduced a new feature called 'Neroku' (Sleep Log). If you wear the 'Sa-Watch' to bed, it will automatically record your sleep. This sleep data is then linked to your preceding sauna session, allowing you to see the correlation with your sleep score.
For example, you can find out: Was there a difference in my sleep on days I went to the sauna versus days I didn't? Did my sleep quality change depending on the time I took a sauna? On which days did I sleep best, and how many sauna sets did I do? By continuing to log your data, you can easily identify which behaviors are impacting your sleep."
Users who have tried the product are already sharing positive feedback, with comments like, "The data proved my intuition was correct!" and "I can now tailor my sauna sessions to match my body's condition."
The Future of the Sauna Experience, as Envisioned by 'Sa-Watch'
Never before has there been a wearable device so completely dedicated to saunas. That's likely why it's been getting so much attention.
Kato had previously appeared on the business video media channel PIVOT to explain the benefits of saunas. However, since the show aired well before the "Sawatches" were scheduled to go on sale, he confessed he was worried about how many people would actually visit their e-commerce site.
"Thanks in part to the support from Gakken, we were able to get our first release into the hands of many people. This time, we were handling sales all on our own, so we were just hoping to sell them steadily, even if it was a small number.
To our surprise, the 3,000 units we had in stock sold out within 15 minutes of the launch. We're now continuing sales by taking pre-orders."
The promise of a more effective sauna experience likely caught the eye of many enthusiasts from the beginning. So, what future feature updates are planned to help grow the sauna community?
"For seasoned sauna lovers, we plan to provide a 'sauna chart' that offers more advanced, personalized data. For newcomers just getting curious about saunas, we'll offer data that clearly explains how to use a sauna and its benefits.
We've also noticed that women tend to be more in tune with managing their health than men. With that in mind, we're currently developing a new design that will appeal to a wider female audience."
Many people hear the word 'sauna' and immediately worry about the physical strain, or perhaps they've tried it and just didn't 'get' the appeal. But as Kato points out, if you can have fun while also preventing illness, it’s certainly worth a try. For anyone on the fence, we highly recommend trying the "Sawatches" and the "Sa no Kuni" app as your personal health management tools.
How was the article?
Share
Related Articles
