Warm-Water Footbathing in Young Women With Cold-Sensitivity Constitution (Hiesho) Increases Parasympathetic Nerve Activity and Promotes Peripheral Circulation.

Background A cold-sensitivity constitution (CSC), termed "Hiesho" in Japanese, is a common condition among young women that impairs quality of life through reduced peripheral circulation and autonomic imbalance. In our previous study, we reported that cold intolerance is associated with an imbalance in autonomic nervous function, as evaluated by heart rate variability (HRV). Conversely, footbathing increases parasympathetic nervous activity (PNA) and increases both peripheral blood flow and epidermal temperature. In the present study, we aimed to compare the autonomic nervous activity and peripheral skin temperatures of young women with CSC using either warm-water or steam footbathing. Methods This study employed a quasi-experimental, cross-sectional design. The participants were 12 healthy young women diagnosed with CSC (six in the warm-water footbathing group and six in the steam footbathing group). All participants reported sensations of coldness, were identified as having CSC via the Coldness Survey Questionnaire, and exhibited contrast between central (tympanic) and peripheral (hallux) body temperature measurements of 6°C. Fifteen minutes before and at 15 and 30 minutes after a 15-minute footbathing, we measured the epidermal temperature at the hallux and dorsal hand. Heart rate variability (HRV) was also assessed. Results The parasympathetic activity index tended to increase in the warm-water footbathing group 15 minutes after footbathing, although the difference was not statistically significant (p=0.065). No statistically significant differences were observed in sympathetic nerve activity index or heart rate between the two (warm-water and steam) groups. The right dorsal hand skin temperature showed an increasing trend in the warm-water footbathing group at 15 and 30 minutes after the footbath, although the difference was not statistically significant (p=0.093 at 15 min, p=0.065 at 30 min). Notably, the right hallux skin temperature increased significantly more in the warm-water footbathing group 30 minutes after footbathing (p=0.026). Conclusion Warm-water footbathing for healthy young women with CSC increased PNA and peripheral skin temperature more effectively than steam footbathing.