BrainSleep Co., Ltd. (Headquarters: Chiyoda-ku, Tokyo; Representative Director: Atsushi Hirota; hereinafter "BrainSleep"), BREATHER Co., Ltd. (Headquarters: Tokyo; Representative Director: Yuki Mikamura; hereinafter "BREATHER"), and 100plus Co., Ltd. (Headquarters: Tokyo; Representative Director & CEO: Hirotaka Kato; hereinafter "100plus") jointly conducted a study on sauna and breathing. The results of the study indicated that consciously incorporating deep breathing may contribute to more efficient autonomic nerve switching during sauna use, leading to a deeper state of "totonou." Background of this Initiative Deep breathing is said to have the effect of regulating the autonomic nervous system and bringing the body into a relaxed state, and it is an important function that also affects sleep. In order to promote the importance of deep breathing, BrainSleep decided to conduct a study on the effects of deep breathing on the body in collaboration with BREATHER, which has always focused on the potential of deep breathing. As the first phase, to verify the potential of deep breathing during sauna use, we collaborated with 100plus and conducted this study at a sauna facility in Tokyo. This study targeted 108 men wearing the sauna-specific wearable watch "SHOWDOWN-1" and measured the effects on the body during sauna use due to changes in breathing habits. In addition, the subjects during the study were asked to incorporate deep breathing (Kihon no Kokyu®), proposed by breathing consultant Takashi Onuki. Study Overview Study period: December 2, 2024 - December 22, 2024 Study locations: Old Rookie Sauna Ginza Chuo-dori, Old Rookie Sauna Shinjuku Station Shin-Minami-guchi Old Rookie Sauna Shibuya Hachiko-guchi Participants: 108 men Measurement device: Sauna-specific wearable watch "SHOWDOWN-1" *1 Study method: "Sauna use with specified breathing method *2" and "Normal sauna use" *1 A sauna-specific wearable watch planned and sold by 100plus that measures heart rate data and calculates the "totonoi value" in conjunction with a dedicated app. *2 Deep breathing (Kihon no Kokyu®) proposed by breathing consultant Takashi Onuki Study Results This study suggested that improving breathing methods optimizes autonomic nerve switching during sauna use, reduces physical burden, enhances the quality of relaxation, and contributes to a deeper state of "totonou." Additionally, incorporating deep breathing resulted in shorter stays in the sauna and resting room compared to normal times. This indicates the possibility of more efficient sauna use, which can lead to practical benefits such as improved facility turnover and increased user satisfaction. Moving forward, continued research with more subjects and validation under different facility conditions are considered necessary. Appendix・Incorporating deep breathing showed an improvement in autonomic nerve activity in the cold bath and resting room. It was found that incorporating deep breathing made autonomic nerve switching more efficient compared to normal conditions (Figure 1). Figure 1 Changes in ccvTP (an indicator of overall autonomic nerve activity) ccvTP = an indicator of overall autonomic nerve activity, less affected by age and heart rate. Higher values are observed in healthy young individuals, and decrease with aging, fatigue, and stress. Generally, high values indicate good autonomic nerve function. ・Incorporating deep breathing in the sauna activated the sympathetic nervous system more than usual, and incorporating deep breathing in the cold bath activated the parasympathetic nervous system. Incorporating deep breathing led to increased sympathetic nerve activity in the sauna. This result suggests that the body may adapt more easily to high-temperature environments. Furthermore, in the cold bath, it was observed that the parasympathetic nervous system became dominant when deep breathing was incorporated. It is thought that deep breathing reduced the burden on the body during cold bath use and enhanced the relaxation effect (Figure 2). Figure 2 Changes in LF/HF (an indicator of the balance between sympathetic and parasympathetic nerves) LF/HF = A higher value indicates sympathetic dominance, while a lower value indicates parasympathetic dominance. It tends to increase under stress. It increases in standing positions or under mental stress, and decreases in supine positions or during relaxation. ・Incorporating deep breathing resulted in shorter stays in the sauna and resting room compared to normal times. By incorporating deep breathing, sauna stay time was reduced by approximately 3 minutes and rest room stay time by approximately 3 and a half minutes compared to normal. This is thought to be because improving breathing techniques allowed for efficient activation of the autonomic nervous system in the sauna and quick transition to a relaxed state in the cold bath. From these results, it can be concluded that by incorporating appropriate breathing techniques for each situation, one can achieve "totonou" efficiently (Figure 3). Figure 3 Changes in stay time (seconds)
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