Objective: Warm water immeresion (WWI) has been customary in Japan as useful thermal therapy. However, a comprehensive investigation of the effects of WWI on internal organs has never been undertaken. The purpose of this study was to examine the effects of single WWI on indocyanine green (ICG) excretion in healthy humans. Subjects: 23 healthy males. (32.6±1.9 [mean±SEM] years) Methods: 1CG was administered intravenously (0.5mg/kg) to calculate excretion rate (ER). ICG injection was given before and after WWI (10min at 41°C). Sublingual temperature (ST), blood pressure (BP), heart rate (HR), and cardiac output (CO) were simultaneously measured by noninvasive methods. Results: Significant changes were observed after WWI. These included an increase in ST, HR, and CO and a decrease in systolic BP (p<0.01). ER significantly decreased from 0.210±0.015 to 0.168±0.009 (p<0.01). Front-back ratio of ICG-ER which was calculated in order to evaluate the effect of aging increased significantly with age (R=0.582, p<0.0001). Conclusion: These results indicate that although CO increased due to the vasodilating effects of WWI, hepatic blood flow decreased after WWI and its response reduced with age even in before middle age.

The effects of the bathing on renal function were studied in 12 healthy men (32.3±7.7y. o.). The subjects took 41°C, 10min bathing and kept warm by a blanket for 30min, and then a mixture of 10% para-aminohippurate (PAH, 0.3ml/kg) and 10% sodium thiosulfate (NTS, 80ml) was infused intravenously. Clearance of PAH and NTS was calculated as the index of renal plasma flow (RPF) and glomerular filtration rate (GFR). PAH and NTS clearance test was also done at rest without bathing in another day. Blood Pressure (BP), Heart rate (HR), cardiac output (CO), sublingual temperature by electric thermista as deep body temperature were measured during the experiment. 30min after bathing, sublingual temperature was significantly increased by 0.9°C, and CO by +40%. After bathing, renal plasma flow (PAH clearance) significantly increased from 388.5±158.9ml/min to 572±170.7ml/min. Glomerular filtration rate (NTS clearance) was, however, unchanged from 115.6±37.3ml/min to 119.3±51.3ml/min. Filtration fraction (GFR/RPF) was significantly decreased. These results indicated that GFR was not improved by bathing although CO and RPF was increased by thermal vasodilation effect. The mechanism of unchanged GFR, despite of increased RPF, is probably that glomerular filtration pressure unchanged by thermal vasodilation of glomerular efferent and afferent arterioles.

Treadmill exercise tolerance test(Modified Bruce Method) was performed with and without warm water bathing (WWB, 41°C, 10min) in 14 healthy aged men and women over 65y. o. (68.6±6.0y.o).
Increase in HR, BP and PRP during exercise was reduced after WWB. Duration of exercise and ST depression and occurrence of arrythmia during treadmill exerecise were significantly improved after WWB. Fatigability of the legs and Borg's index were also decreased aftr WWB. These results indicated the improvement of exercise tolerance after WWB was probably due to the increase in cardiac functions and collagenous viscosity (extensivility) of the musculoskeletal system.

The effects of high concentration mineral water bating (31.16g/kg, mainly composed of Na, Ca, Mg chloride and sulfate) were studied in 13 healthy men (44.9±16.3y.o.). The subjects took 41°C, 10min bathing and kept warmth by a blanket for 30min. Blood pressure (BP), Heart rate (HR), cardiac output (CO), total peripheral resistance (TPR) and sublingual temperature by electric thermista as deep body temperature were measured during and after bathing. Skin blood flow by LASER doppler flow meter and venous partial gas pressure and pH were also measured.
Sublingual and forehead temperature was increased significantly by +1.4°C after 10min bathing and +0.9°C increase continued even after 30min. Diastolic BP and TPR were significantly decreased, and HR and CO were significantly increased by +20bpm and +2.7l/min, respectively. Significant increase of skin blood flow was also demonstrated. Significant increase of venous pO₂ (+20 Torr) and decrease of pCO₂ (-8.0 Torr) suggested the improvement of peripheral oxidative metabolism due to increased CO.
High concentration mineral water bathing was highly effective than simple water bathing probably due to the thick coating effect by binding concentrated minerals with skin furface protein.

Phthalides and ligustilide in Senkyu extract and limonene and fravonoids in Chimpi extract have been reported to have strong vasodilation effects.
In the present study the circulatory effects of Senkyu and Chimpi extract (crude drug extract) were studied as bath agent in 40.0°C bath water (Senkyu ext. 224mg and Chimpi ext. 272mg/2001). Thirteen healthy men (36.2±5.8 years old) took a bath at 40.0°C for 10 min with and without (only with flavor and dye) crude drug extract and the circulatory effects were followed for 30 min after bathing.
Heart rate and cardiac output were increased equally by 10 min bathing either with or without crude drug extract. Although systolic blood pressure was slightly increased during bathing, diastolic blood pressure and total peripheral resistance were significantly decreased during and after bathing with and without crude drug extract. Forehead skin blood flow and sublingual temperature were significantly increased during bathing, and remained at higher level for 10-30 min after bathing with crude drug extract. Venous blood pO₂ and pH were significantly increased and pCO₂ was decreased equally with and without crude drug extract. Plasma NE was significantly increased by bathing with crude drug extract.
Bath agent with Senkyu and Chimpi extract are considered favorable as bath agent to keep high skin blood flow and sublingual temperature probably due to its vasodilating effects.