Japanese steam sand bath heat therapy mediates comparable reductions in blood pressure with smaller discomfort and respiratory strains than hot water immersion and sauna.

PURPOSE: Heat therapies such as hot water immersion, Finland saunas, and Waon therapy have been reported to reduce resting arterial blood pressure. However, hyperthermia imposes physiological and perceptual strains. To acquire a habit of heat therapy, it is ideal to develop a modality that offers therapeutic benefits with minimal strain. Here, we hypothesized that the unique Japanese traditional steam sand heat therapy lowers blood pressure with minimum physiological and perceptual strains.

METHODS: Fourteen healthy young male adults underwent three heating procedures, each lasting 20 min: (1) steam sand bath (~ 50 °C), (2) hot water bath (~ 41 °C), or (3) sauna (~ 80 °C) in a randomized counter-balanced manner. Cardiorespiratory responses and perceptions were assessed before, during, and after each heating.

RESULTS: Core temperature increased in the following order: hot water bath > sauna > steam sand bath (all p < 0.001 at end heating). Partial pressure of end-tidal carbon dioxide remained stable during the steam sand bath, whereas it decreased in both the hot water bath and sauna conditions (both p < 0.001 at end heating). Mean and diastolic arterial blood pressures declined at the end of recovery (all p < 0.001), with similar responses across conditions (all p > 0.39). Thermal comfort at the end of heating was lower (i.e., more comfortable) in the steam sand bath compared to the other two conditions (both p < 0.001).

CONCLUSION: We show that the traditional Japanese steam sand bathing may provide blood pressure-lowering benefits with reduced respiratory and perceptual strains compared to hot water bath and sauna.