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

purposeHeat 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.

methodsFourteen 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.

resultsCore 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).

conclusionWe 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.