We investigated the effect of hot bath and infrared radiation on tonic muscle discharges due to hypertonia in the affected upper extremity of hemiplegic patients using surface electromyography (EMG). Subjects were 15 hemiplegic patients with cerebrovascular diseases. The subjects were selected on the basis of the presence of considerable rigidospasticity in the biceps brachii muscle (BBM). Hot bath (42°C) was applied for more than 3 minutes in the supine position with the cubital joint fixed in flexion in 11 subjects. Infrared radiation (300 watts) was applied to the flexor side of the affected upper extremity in the same posture in 13 subjects. Surface EMGs of the BBM and triceps brachii muscle (TBM) were recorded bipolarly with waterproof disc electrodes before, during, and after the trials of hot bath and infrared radiation. The recorded EMG was rectified and integrated, and then converted into sequential pulses. The amount of EMG was calculated as the number of pulses. The EMG of the affected side was normalized as a percentage of the amount versus that of the unaffected side in maximum voluntary contraction. The EMGs of the BBM and TBM showed tonic muscle discharges in all subjects in the resting state. The EMGs of the BBM and TBM averaged 6.4% and 1.4% before hot bath and 3.3% and 1.2% before infrared radiation. The EMG of the BBM in the third 1 minute during hot bath decreased by 58.8% (p<0.01) and increased slightly after the trial. The EMG of the TBM during hot bath increased insignificantly, and decreased by 25.3% (p<0.05) in the second 1 minute after the trial. The EMGs of the BBM and TBM in the third 1 minute during infrared radiation decreased by 31.9% (p<0.01) and 9.3% (p<0.05), and the decrease persisted after the trial. The results demonstrated that thermotherapy, especially hot bath, decreases the tonic muscle discharges due to rigidospasticity.

We have pointed out that the incidence of cerebral and myocardial infarction that occur early in the morning is high and estimated its correlation with blood viscosity as a cause. To clarify the mechanism of onset of such diseases early in the morning in further details, we examined the effect of alcohol drinking and hot spring bathing on the circadian changes in blood viscosity on normotensive and nonsmoking young men. It was observed that both drinking a bottle or 633ml of beer containing 4.5% alcohol and taking a hot spring bath at 42°C for 10 minutes at 8p.m. tended to enhance the rate of increase in blood viscosity between 4a.m. and 8a.m. the next morning as compared with the control. In contrast, drinking 500ml of water at 0a.m. after either drinking a bottle of beer or having a hot spring bath mitigated the change in blood viscosity the next morning. These findings may suggest that both drinking alcohol and taking a hot spring bath around dinner time elevate the rate of increase in blood viscosity in the next morning, leading to possible onset of cerebral and myocardial infarction. Drinking two glasses of water at midnight is effective in preventing such change in blood viscosity in the morning.

Many researchers have pointed out that CO₂ bathing directly effects expanding dermal vessels. The authors have recently reported a decrease in red blood cell after CO₂ bathing. To clarify other effects of CO₂ bathing on RBC, the changes in the hemoglobinoxygen-dissociation curve (P50) were measured after single bathing (for 10 minutes at 40°C) with artificial CO₂ water made of sodium bicarbonate and citric acid dissolved in plain water. P50 was measured with an oxygen-dissociation analyzer (HEMO-O-SCAN^TM made by American Instrument Company) and 2, 3-diphosphoglycerate (2, 3-DPG) in RBC, with enzymatic analysis. The subjects of this study consisted of six male patients and four female patients, ranging from 53 to 80 years old.
The results are presented below.
1) Nine of ten patients showed an increase in P50 after 15 to 30 minutes of CO₂ bathing. The remainder showed a transient increase in P50.
2) No significant increase in 2, 3-DPG concentration in RBC was found in the group subjected to CO₂ bathing as compared to that of the controls who were subjected to plain water bathing. However, seven patients showed an increase in 2, 3-DPG after 15 to 30 minutes of CO₂ bathing, and three patients showed a decrease in 2, 3-DPG.
3) Partial pressures of oxygen (PO₂) and carbon dioxide (PCO₂) in the venous blood were measured. Elevation of PO₂, lowering of PCO₂, and increase in pH were observed in almost all patients after a single CO₂ bath.
From these results, we can conclude that a single CO₂ bath effectively decreases oxygen affinity of hemoglobin, presumably due to a rise in the blood temperature and partially due to an increase in 2, 3-DPG concentration in RBC.