Background
Bathing in hot water is very common in Japan; people bathe in order to clean their bodies and to recover from physical and mental fatigue. However, there have been few reports examining the effects of bathing on recovery from mental fatigue. The purpose of this study was to examine the effects of mild-stream bathing on recovery from mental fatigue.
Material and Method
During mild-stream bathing, a mild stream continuously passes from the sole to the calf, thigh, waist and back, thus providing a massage function. In a double-blinded, placebo-controlled, crossover experiment, 14 male healthy volunteers were randomized into normal bathing and mild-stream bathing experiments. After a fatigue-inducing mental task for 4 hours, subjects took a normal or mild-stream bath.
Results
Heart rate was higher, muscle stiffness in the waist was lower and plasma cortisol levels tended to be lower after mild-stream bathing when compared to normal bathing. In addition, after mild-stream bathing, mental task performance, as assessed by reaction times on an advanced trail making test, was better than that after normal bathing.
Conclusions
The present results suggest that improved working memory processing, diminished waist muscle tone, and attenuated mental stress are induced by mild-stream bathing. Therefore, mild-stream bathing appears to be more effective for alleviating mental fatigue than normal bathing.

Keywords: Muscle, Skeletal - physiology, Mental Fatigue - therapy, Japan, Hydrotherapy - statistics & numerical data, Hydrocortisone - blood, Heart Rate, Double-Blind Method, Cross-Over Studies, Analysis of Variance, Psychomotor Performance