The direct effect of bathing on R-R interval was examined in six healthy men (mean age, 40±11 years).
Bathing at 37-38°C produced signifficant shortening of mean R-R intervals (mRR) during usual and deep breathing (6times/min), and signifficant decrease of their coefficients of variation (CV; SD/mRR×100) during deep breathing.
In ten minutes after the end of bathing, mRR recovered, but not CV.
These data suggest that the bathing at those temperature might stimulate the sympathetic drive and suppress the parasympathetic drive to the heart.

The finger skin temperatures at ventral tip of both sides were examined in 8 normal subjects and 20 patients with vibration disorder, during one hand 45°C-water immersion test of 10 minutes.
In normal cases, the figer skin temperatures of the immersion side increased immediately and then waved from time to time during the immersion. The mean temperature at the time of 4.5 minutes was significantly higher than those of 2.5 minutes and 8.0 minutes and did not come near the 45°C graduary.
In the patients with vibration disorder who had got Raynauds' phenomenon with in a recent year, the skin temperatures did not so waved as which did in normal cases and became near the 45°C in the later half of the immersion. After the immersion, the warmed skin temperatures returned more slowly to their previous values than the normal cases.
The finger skin temperatures of the non-immersion side showed transient but significant falls initialy and then got up gradualy during the immersion in the normal cases.
In the patients with vibration disorder who had got Raynauds' phenomenon, within a recent year, the mean skin temperature of the non-immersion side was significantly lower than the normal value almost before, through and after the immersion especialy in the later half of the immersion and for several minutes after the immersion. The initial fall of skin temperatures were not so obvious as they were in the normal cases.
These data suggest that the hot water immersion test is useful to asess the peripheral circulatory disturbance in patients with vibration disorder.

This study examined acute effects of hot water immersion on the secretion of human alpha-atrial natriuretic peptide (ANP), cyclic GMP (c-GMP), arginine vasopressin (AVP), plasma renin activity (PRA) and aldosterone in venous blood. Ten healthy subjects (mean age: 20.5yr.) underwent hot water immersion (IM) of 40°C for ten minutes by quiet sitting, which simulates usual bathing among Japanese. ANP rose from 19 to 34pg/ml with the peaked value at ten minutes of IM (p<0.001), and remained signifcantly elevated during 10 to 30 minutes after IM. Then they qradually returned to the pre-immersing level by 50min. c-GMP showed similar timed responeses as ANP. Between those parameters significantly positive linear correlation (p<0.001) was observed. AVP did not change immediately after IM, but tended to rise at 20 minutes after IM. PRA and aldosterone increased in rates of the changes later at 15 to 30 minutes, but less significantly as ANP. Those results suggested that the secretion of ANP by water immersion was enhanced by thermal stimuli in spite of short duration of central hypervolemia by water immersion. Suppressing effects of water immersion on AVP and renin-aldosterone system were small. On the contrary, hot water stimuli exerted rebounding increases on them. c-GMP seemed to be one of the indicative factors relating to the change of ANP.

The effect of underwater exercise on respiratory resistance (Rrs) was examined in 12 patients with chronic obstructive pulmonary disease (COPD). Rrs was measured while the patients were sitting on land with quiet respiration, while immersed in water (at 38°C) up to the upper abdomen and upper chest in standing position, and while sitting on land with quiet respiration after mild underwater exercise. The mean Rrses in each condition were 0.37, 0.37, 0.42, 0.33kp/1/s. Rrs increased by 14% (p<0.005) after immersion in water up to the upper chest and decreased by 12% (p<0.001) after underwater exercise. The change after exercise showed a popitive correlation with FEV_1.0/FVC on spirogram. Although water immersion or underwater exercise of these COPD patients caused a slight load in ventilation, no significant aggravation of the subjective symptom was found.
The above results suggested that uoderwater exercise was beneficial as a physical treatment for mild cases of COPD.

Usefulness of balneotherapy in diabetics were discussed. Plasma glucose levels in diabetics treated with insulin decreased significantly after thirty minutes exercise under 38°C hot springs pool. There were positive relationships on plasma glucose levels between before and after exercise in hot springs. Lipids metabolism were improved during three months' balneotherapy. The ratio of VLDL·LDL-cholesterol/HDL-cholesterol decreased. Basal levels of plasma cyclic AMP decreased slightly and plasma cyclic GMP significantly increased. Intrathecal injection of vitamin B₁₂ (mecobalamin, 2500μg) was apparently effective to reduce the pain on under limb in patients with diabetic peripheral neuropathy whose subjective symptom could not improved by any medications. The effect of mecobalamin was increased by bathing in hot springs. Usually, balneotherapeutic hospitals have facilities of rehabilitation system in Japan.
In conclusion, the balneotherapy by adding physical treatment is very benefit to normalize carbohydrate and lipid metabolism. Tranquilizing function of hot springs are effective on psychological disturbance, diabetic autonomic and peripheral neuropathy.