We studied the mechanism for slowing surface electromyography (EMG) during fatiguing contraction using superimposed M-wave analysis. Seven healthy male subjects exerted 60% maximum voluntary contraction of isometric abductions in the left first dorsal interosseous muscle (FDI) until exhaustion. Simultaneously with voluntary contractions, the ulnar nerve was electrically stimulated at supramaximal intensity, and volitional EMG and superimposed M-waves were obtained. We examined the behavior of muscle fiber conduction velocity (MFCV) and median frequency (MDF) for both EMG, with the following results:
1) MFCV calculated from volitional EMG of FDI was about 6 m/s during 60% MVC.
2) The waveform of voluntary EMG detected from FDI slowed in all subjects during fatiguing contraction at 60% MVC, indicating fatigue had developed in the muscle.
3) As fatigue progressed, the waveform of the superimposed M-wave tended to decrease in amplitude and increase in duration.
4) As fatigue progressed, MDF and MFCV in volitional EMG decreased significantly (p<0.04) . The rate of change was larger in MDF than in MFCV (p<0.01) .
5) As fatigue progressed, MDF and MFCV in the superimposed M-wave decreased significantly (p<0.01) . The rate of change was larger in NIDF than in MFCV (p<0.05) .
These results suggested that MFCV and other peripheral factors affected the slowing of volitional EMG. Elongation of the depolarization zone in muscle fiber is proposed as a peripheral factor.

The purpose of this study was to examine the effects of short-term immobilization on the maximum voluntary contraction (MVC) force. The first dorsal interosseus (FDI) of 10 healthy male adults was immobilized for 1 week using casting tape. Atrophy of the muscle was estimated from a cross sectional view of magnetic resonance images (MRI) . To clarify the factors of a peripheral neuromuscular system contributing to the change in the MVC force, twitch force at rest was measured. The contribution of central factors was estimated from a voluntary activation (VA) index, which was obtained by the twitch interpolation method.
The MRI showed no significant changes in the cross sectional area. The MVC force declined after immobilization (p<0.01), and recovered after 1 week from the termination of immobilization (p<0.01) . Both the twitch force at rest and the VA at MVC declined after immobilization (p<0.01), and recovered after 1 week (p<0.05) .
The results indicate that the temporary decline of the MVC force was not accompanied by atrophy of the muscle. Furthermore the decline of the MVC was caused both by the deterioration of peripheral and central functions in the neuromuscular system. Possible factors in the peripheral and central neuromuscular systems affected by the immobilization were discussed.

We evaluated motor unit (MU) fatigue in the first dorsal interosseous muscle (FDI) using the collision principle. Eight healthy men exerted 70% (short-duration fatigue task: SDF task) and 30% (long-duration fatigue task: LDF task) maximum voluntary contraction of isometric abductions in the left FDI until exhausted. Before and after voluntary contractions, the ulnar nerve was stimulated at the wrist and elbow with supramaximal intensity, and a pair of M-waves was obtained. Fatiguerelated changes were studied in mean power frequency (MPF), averaged rectified value (ARV) calculated from surface EMG, and motor nerve conduction velocity (MCV) and distribution of motor nerve conduction velocity (DMCV) calculated from M-waves. The MPF of voluntary EMG decreased, whereas ARV increased significantly during SDF and LDF tasks, indicating fatigue had developed in the FDI. Endurance was significantly shorter in the SDF task than in the LDF task (p<0.01), whereas differences between tasks were not seen in MPF and ARV changes. Tasks did not affect MCV, but lower components in DMCV increased for both tasks. Increased lower components were larger in the LDF task than in the SDF task. The shift in DMCV indicated that fatigued MUs stopped activity and enduring MUs, which had lower axon conduction velocity, were activated selectively. These results suggest that the collision principle is applicable in evaluating motor unit fatigability.

Effects of spa therapy on asthma were studied in 64 patients with asthma in relation to the generation of leukotrienes B4 (LTB4) and C4 (LTC4) and bronchial hyperresponsiveness. 1. The efficacy of spa therapy was marked in 12 (18.8%), and moderate in 45 (70.3%) of 64 patients with asthma, and slight or no efficacy of the therapy was observed in the residual 7 patients (10.9%). 2. Bronchial hyperresponsiveness to methacholine was the highest in patients with slight or no efficacy of spa therapy, however, there were no significant differences among the three groups classified by clinical efficacy. 3. The generation of LTC4 by leucocytes was significantly higher in patients with slight or no efficacy compared with the generation in those with marked (p<0.01) and moderate efficacy (p<0.001). However, there were no significant differences in the generation of LTB4 among them. 4. The generation of LTC4 before spa therapy significantly decreased in patients with marked (p<0.001) and moderate efficacy (p<0.01) after spa therapy, but not in those with slight or no efficacy. The generation of LTB4 was not significantly different before and after spa therapy among patients with marked, moderate, and slight or no efficacy. These results show that the efficacy of spa therapy for patients with asthma is closely related to the generation of LTC4 by leucocytes, and that the generation of LTC4 significantly decreases after spa therapy in patients with spa efficacy.

Characteristics of low attenuation area (LAA) of the lungs on HRCT were studied in 132 patients with asthma, and long-term spa therapy on the LAA of the lungs was observed in 5 patients with asthma, whose me an %LAA was more than 30%.
1. The morphology of LAA of the lungs on HRCT observed in asthma was different from that in pulmonary emphysema. 2. The LAA of the lungs in asthma was closely related to residual volume (RV). 3. The mean %LAA value significantly decreased from 33.5% before spa therapy to 24.5% at 24 months after beginning of the therapy. CT number also significantly increased after long-term spa therapy. 4. %FEV1.0 value significantly improved from 52.1% before spa therapy to 72.1% at 24 months after spa therapy. The RV value also decreased by spa therapy, however, the decrease was not significant. These results suggest that LAA of the lungs in asthma is associated with hyperinflation, and the LAA of the lungs decreases after long-term spa therapy.

Clinical effects of spa therapy for patients with pulmonary emphysema (PE) were evaluated by observing changes in %LAA of the lung on HRCT, %RV, %FVC, %FEV 1.0, and %DLco values after the long-term therapy. The subjects in this study 16 patients with PE. The subjects were divided into two groups according to the extent of %LAA<-950 HU of the lung on HRCT: %LAA<50% (N=6) and 50%≤%LAA (N=8). 1. Spa therapy significantly improved %LAA (42.5% at the initial stage to 36.3% 24 months after spa therapy), %RV (202.1% to 156.1%) and %DLco 71.0% to 85.7%), but not %FVC and %FEV 1.0, in patients with PE of %LAA<50%, however, significant. Improvement of these parameters was not observed in patients without spa therapy. 2. Spa therapy did not improve the values of %LAA, %RV, and %DLco, as well as %FVC and %FEV 1.0, in patients with PE of 50%≤%LAA. These parameters tended to decrease in the patients of 50%≤%LAA. These results suggest that spa therapy improves %LAA and parameters related to pulmonary function when they are at early stage of PE, however, the therapy was not remarkably effective for these parameters when they were at advanced stage of PE.

Spa therapy has been performed at our medical center for last 20 years. The changes in number and frequency of patients with respiratory disease were analyzed every 5 year for last 20 years. The total number of patients with respiratory disease who were admitted at our medical center for last 20 years was 1934, of whom the number of patients with asthma was 1226 (63.4%), and the number of those with COPD was 415 (21.5%). The number of patients with asthma treated with spa therapy showed a tendency to increase form 57 for the first 5 years (first stage) to 465 for the last 5 years (forth stage). The number of patients with COPD also increased from 26 for the first 5 years to 227 for the last 5 years. The frequency of SDIA decreased from 68.4% for the first 5 years to 29.0% for the last 5 years. In contrast, the frequency of pulmonary emphysema increased 19.2% at the first stage to 76.7% at the forth stage. The number and frequency of elderly patients with asthma and COPD over the age of 60 tended to increase for last 20 years.

N-3 fatty acids are reportedly effective for asthma. In addition, spa therapy has been reported to be effective for patients with asthma. In the present study, the effects of spa therapy combined with perilla seed oil-rich diet (rich in n-3 fatty acid) were examined on asthma. A total of 14 asthmatic patients had a complex spa therapy and consumed a perilla seed oil-rich diet-rich in α-linolenic acid (α-LNA) for 8 weeks. Generation of leukotriene (LT) C4 by leucocytes, respiratory function were analyzed. The generation of LTC4 by leucocytes decreased significantly for 2, 4 and 8 weeks (P<0.05). Peak expiratory flow (PEF) values increased significantly for 2, 4, 6 and 8 weeks (P<0.05). The values of ventilatory parameters [forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), forced expiratory flow after 25% of expired FVC (FEF₂₅), forced expiratory flow after 75% of expired FVC (FEF₇₅), mean expiratory flow during the middle half of the FVC (FEF_25-75)] revealed a significant increase after 4 and 8 weeks of the modified diet (P<0.05). The results suggest that spa therapy combined with a perilla seed oil-rich diet are effective in the treatment of asthma in terms of its ability to suppress LTC4 generation by leucocytes, and in inducing an improvement of pulmonary function.

The patients with asthma or pulmonary emphysema who were admitted at our hospital for last 9 years (1992-2000) were examined in relation to frequency of disease, patient age, and areas where patients came.
1. Of 1271 patients (141.2 patients/year) with respiratory disease admitted for last 9 years, 808 (63.6%, 97.8 patients/year) were patients with asthma, and 157 (12.4%, 17.4 patients/year)) were those with pulmonary emphysema.
2. The frequency of patients with asthma for all patients with respiratory desease tended to decease from 82.1% in 1992 to 51.3% in 2000, while the frequency of those with pulmonary emphysema increased from 2.8% in 1992 to 24.4% in 2000.
3. The number of patients with asthma over the age of 70 years was larger in those inside Tottori prefecture, and the number of patients between the ages of 60 and 69 years was larger in those from distant areas. The age was more than 50 years in all patients with pulmonary emphysema.
4. The number of patients with asthma from distant areas (outside Tottori prefecture) was larger (456 patients; 56.4%) than the number of those inside Tottori prefecture (352 patients) for 9 years. The number of patients from Okayama, Hiroshima, Hyogo and Osaka was larger than the number from other distant areas.