To clarify a mechanism of psychologic relaxation by artificial hot spring, the effect of hot spring bathing on psychologic sweating was studied in 11 healthy subjects (1 female and 10 males, age 26±5.7 years). After lying in the supine position for 5 minutes, the subjects were asked to take a bath with plain water or artificial hot spring for 5 minutes in the sitting position. The temperature of the bath was 40°C. To prepare the artificial hot spring, sodium sulfate tablet (Tsumura & Co.) was solved in 200L of plain water. For the measurement of psychologic sweating, Perspiro (Suzuken, Co. Ltd) was used. Sensor was attached to the first finger by biphasic adhesive tape. The psychologic sweating was induced by deep respiration, mental arithmetic, hand grip, blood pressure measurement and blood sampling. There were no statistical significant differences of CV value, heart rate, blood pressures, catecholamine values and serum β endorphin levels before and after the bathing. The psychologic sweating markedly decreased after the bathing (11.5±19.6 to 1.1±2.7 for plain water bathing, 14.9±21.9 to 1.6±5.1 for artificial hot spring, N. S.).
The decrease in psychologic sweating after bathing suggests the action of psychologic relaxation by bathing.

Change of digital blood flow during sodium sulfate bathing was studied using laser Doppler flowmeter. The 10 subjects were divided into two groups; group A and group B. In group A, digital bloood flow was measured in the following order; in the air→plain water→air→sodium sulfate bathing→air, while in group B, in the air→sodium sulfate bathing→air→plain water→air. The temperature of the water was kept at 40°C using thermostat. The 10g of sodium sulfate was dissolved in the 10L of water. In group A, the digital blood flow was 60.2±16.7 in the plain water and 70.6±35.0 in the sodium sulfate water, while in group B, 30.4±12.7 in the sodium sulfate water and 7.36±10.06 in the plain water (P<0.05).
Above results suggest an increase in digital blood flow in the sodium sulfate bathing, although there were great differences by individual and by the order of immersion.

The purpose of this study was to clarify the effect of warm water bathing (40°C) of the hand on the psychologic sweating measured in the opposite palm. The subjects were 2 males and 4 females, aged 38±10 years (26-58 years). The psychologic sweating was estimated by the apparatus developed by Sakaguchi et al (Sakaguchi, M. et al BME 26: 213, 1988). The room temperature was 27 to 28°C and the relative humidity was 60 to 70%. The sensor was attached using adhesive tape on the right palm. Then the psychologic sweating was measured after deep respiration, mental arithmetic, hand grip, bathing in warm water of 40°C at the level of left wrist. The results showed that the mean values of palmar sweating were 15.6 for deep respiration, 16.8 for mental arithmetic, 15.5 for hand grip and 0 for warm water bathing.
Above results suggest that local water bathing of moderate temperature induces a decrease of psychologic sweating, probably due to relaxing effect of the cerebrum.

The effects of bathing with artificial sodium sulfate on the systolic blood pressure and the level of atrial natriuretic peptide (ANP) in plasma and or in atrium of spontaneously hypertensive rats (SHR) were studied. The following results were obtained:
1) As a result of bathing for 20 minutes at a temperature of 37°C, the systolic blood pressure lowered and the plasma ANP level increased. The blood pressure lowered with increasing concentration of sodium sulfate (p<0.01).
2) The plasma ANP level in a standing position for 20 minutes decreased than in a normal position.
3) The plasma ANP level in SHR was higher and increased more clearly by bathing, compared to the previous results in normotensive rats (WKA). The blood pressure lowered far more in SHR than in WKA.
4) The atrial ANP level was not significantly influenced by bathing nor by changing the posture.
These results indicate that the artificial sodium sulfate bathing has more potent hypotensive effect than plain water bathing probably due to prevent heat radiation, and affects the blood pressure and the plasma ANP more significantly in SHR than in WKA. In addition, the effects of mild bathing to cardiovascular and neurohumoral systems may modulate directly or indirectly the ANP secretion.

The effect of bathing with artificial sodium sulfate on changes in the systolic blood pressure and the level of atrial natriuretic polypeptide (ANP) in plasma or atrium of normotensive male rats was studied. The following results were obtained:
1) As a result of bathing for 20 minutes at a temperature of 37°C, the systolic blood pressure lowered and the plasma ANP level decreased. The blood pressure lowered most clearly after artificial sodium sulfate bathing at a prescribed concentration (p<0.5), while the plasma ANP level decreased significantly after plain water bathing (p<0.01).
2) The atrial ANP level showed no significant change. Presumably the reason was that the quantity of atrial ANP was so large that it was not affected by fluctuations in the peripheral ANP level.
3) The temperature and duration of bathing, the concentration of bath salts, and other factors might also influence the plasma ANP level.
These results suggest that the artificial sodium sulfate bathing lowers the blood pressure by preventing heat radiation from the skin and by delicate regulatory mechanisms on ANP secretion.

The effects of artificial sodium sulfate bathing on cardiopulmonary and neurohumoral systems as compared to plain water bathing were studied on five healthy subjects. The results of bathing tests made for 10 minutes at 42°C were as follows:
1) The body surface temperature was higher in three of the five subjects in artificial sodium sulfate bathing than in plain water bathing. The forehead temperature of all subjects in artificial sodium sulfate bathing was higher than in plain water bathing (p<0.05: at 17, 18min. after bathing). The change in oral temperature also showed the same tendency (p<0.05: at 27min. after bathing).
2) The frequency of respiration was less in artificial sodium sulfate bathing than in plain water bathing. Although the heart rate decreased during artificial sodium sulfate bathing as compared to the case of plain water bathing, a clear difference was not observed after bathing. The systolic blood pressure in four of the five subjects decreased in artificial sodium sulfate bathing compared to plain water bathing. One subject, who exhibited low blood pressure before bathing, was restored to his normal blood pressure after artificial sodium sulfate bathing. The sysytolic blood pressure was lower in artificial sodium sulfate bathing than in plain water bathing. (p<0.03: at 20min. after bathing).
3) The serum levels of noradrenalin, adrenalin, serotonin, ADH, renin, aldoster-one, cortisol, β-endorphine, Na⁺, K⁺, and Cl^- showed no significant differences between the two types of bathing.
4) All subjects felt increased warmth and smoothness of the skin after the artificial sodium sulfate bathing compared to plain water bathing.
The above results suggest that the artificial sodium sulfate bathing is superior to plain water bathing in maintaining body temperature, decreasing blood pressure, and feeling (i. e., body warmth and skin texture) after bathing. These effects result from not only the direct action on the skin but also the indirect action due to absorption of the substance through the skin by the mechanism of artificial sodium sulfate bathing.