The purpose of the present study is to investigate the influence on postural sway of such condition as fatigue resulting from muscular work. Twelve of the male adults (26.7±6.2 yrs old) of a certain airport ground service company were served as the experimental subjects. The measurement of postural sway has been made by measuring the weight at two points of the supporting platform. The degree of postural sway was calculated by using an electronic computer (HITAC-10) . The measurement was carried out before and after the work on each day during the experimental days. The following results were obtained.
On the 1st day with eyes open the ratio of the postural sway after the work to that of before the work (‘after’/‘before’) was 1.25, with eyes closed 113, respectively. On the 2nd day with eyes open it was 1.38, with eyes closed 1.53, respectively. On the last day with eyes open it was 147, with eyes closed 1.23, respectively. The amount of postural sway after the work was greater as compared with that of before the work. The statistical analysis showed that these difference in postural sway was significant (P<0.05-0.001) . The influence of several factors on the changes in postural sway was discussed, together with the experimental results obtained by other authors. In conclusion, these results suggest that balance impairment is mainly due to work-related fatigue.

The purpose of the present study is threefold : first, to observe simultaneously the changes in both the frequency of motor unit (MU) discharges and the amplitude of surface electromyogram (EMG) during the prolonged and sustained voluntary efforts; and second, to demonstrate the effects of arterial occlusion on the frequency of MU discharges ; lastly, to discuss the mechanism of motor control in the light of the present results and others'. Two male adults participated in the experiment. They were with no nervous disorders, right-handed, aged 24 and 33 years. Each subject was seated with both eyes closed in a chair in an electrically shielded room. He held a weight of 1 kg on his wrist during periods of about 45 minutes. The angle of his elbow joint was maintained at 90 degrees during the course of the experiments. The impulses of MU and the surface EMG were led off from muscles biceps brachii of the left upper arm by using coaxial needle electrodes and surface ones respectively. Discharge intervals of MUs were recorded as ordinate by means of ‘Electro-tachograph’. The action voltages of single MU was monitored for differentiation from that of others with a cathode-ray oscillograph and with a loud speaker. The subject's complaints were noted during the course of the experiments. The following results were obtained.
1. The patterns of changes in the frequency of discharges of MUs were divided into three types. The first pattern showed the steep decrease in the frequency of discharge for short period, and at last the discharge disappeared, the second the gradual prolongation of discharge intervals and the increase in both irregular fluctuation and slow undulation, the third constant frequency of discharge even immediately before the exhaustion of voluntary effort.
2. The undulation and prolongation of discharge intervals appeared during the abolition of blood supply to the arm. It did not recover for about 1 minute even though the arterial occlusion was released.
3. The gradual increase in the amplitude of direct EMG in muscles biceps brachii was observed during holding a weight of constant load.
4. The rotational activity of MU was suggested to exist in the case of prolonged, sustained and voluntary muscular contraction.
5. The gradual increase in prolongation and undulation of MU seems to come from the decrease in number of afferent impulses resulting from fatigue.

The purpose of the present study is to investigate the changes in postural sway (PS) related to age quantitatively. The movement in the center of gravity of the body projected into the base of support was used as a criterion of PS. It was measured in 45 subjects, 23 males and 22 females, ranging in age from 22.1 to 68.1. The subjects maintained erect posture with feet together for about 2 minutes with eyes open, and thereafter with eyes closed respectively. The measurement of PS has been made by measuring the weight at two points of the supporting platform. The degree of PS was calculated by using an electronic computer (HITAC-10-II) . The following results were obtained.
1. The displacements of body's center of gravity per 1 minute with eyes open as well as with eyes closed increased with age. The PS, however, showed a gradual increase with eyes open, and then it did a steep increase with eyes closed from the age of fifties.
2. The PS was reduced to two components, i.e., lateral (X) and antero-posterior (Y) ones. The ratio of the Y component to the X one (Y/X) with eyes open as well as with eyes closed showed a gradual decrease with age.
3. The ratio of X component with eyes closed to that with eyes open was calculated as well as the ratio of Y component. At all ages the ratio in X component was larger than that in Y component.
4. Judging from both the steep increase in PS with eyes closed and the gradual increase with eyes open with age, there seems to exist the modification of static equilibration mechanism in the aged, especially the much degradation of some regulatory function other than visual one.

The effects of visual information about object size on grip force programming were investigated. Fifteen subjects (26.1±7.6 yrs) repeated lifts of a cube-like grip apparatus (30×30×30 mm, 30g) using a thumb and index finger, while three boxes of different sizes but equal weight (small : 10×10×60 mm, medium : 30×30×60 mm, large : 60×60×60 mm, 25g) were pseudorandomly presented by attaching beneath the grip apparatus. Lifting tasks were performed in two visual conditions. In the full-vision condition, subjects could perceive the box size prior to the lift-off of the grip apparatus, similar to normal everyday conditions. In the obstructed-vision condition, subjects could not perceive the box size due to the placement of a screen during the initial lifting phase, and only the grip apparatus were visible over the screen. The grip apparatus measured grip and load forces during the trial and we found that the grip and load force applied to the grip apparatus in the full-vision condition significantly increased with box size regardless of equal weight. In contrast, when the size information was removed in the obstructed-vision condition, the force applied for a given box of any size was always that adequate for the largest box, suggesting that the scaling of fingertip force by utilizing size information may be achieved by reducing forces for the smaller boxes on the basis of the force output applied for the largest box, but not by increasing forces on the basis of the force output applied for the smallest box.

The present study was conducted to examine whether stretching was effective to control muscular atrophy.Subjects were eight male undergraduate students (height 171.4 ± 5.8 cm, body weight 72.2 ± 7.8 kg, and age 20.6 ± 1.1 years) and the muscle analyzed was the vastus lateralis.Firstly, the subjects were instructed to perform strength training for a period of 16 weeks, which was followed by a 12-week detraining period. During the detraining period, either the right or the left leg was stretched daily for 10 minutes (2 sets). The mass of the vastus lateralis muscle was estimated based on its cross-sectional area (CSA), as assessed by magnetic resonance imaging (MRI). Relative decreases in muscle mass were compared between the stretched and the non-stretched control leg.Muscle mass in the non-stretched leg showed significant decreases during detraining, while no significant decreases in muscle mass were detected in the stretched leg. This outcome indicates that stretching can influence muscle plasticity and, therefore, is effective for preventing decreases in muscle mass.In conclusion, this study suggests that, added to its known ability to improve flexibility, accelerate recovery from fatigue, and prevent injuries, static stretching is effective for controlling muscle atrophy.

We report a case of redo aortic valve replacement by right minithoracotomy approach for aortic stenosis after coronary artery bypass grafting (CABG). An 81-year-old man was followed-up once a year for 9 years after CABG. He complained of increasing respiratory distress, showed narrowing of the aortic valve area, elevation of the aortic valve pressure gradient, and tricuspid valve regurgitation by echocardiography. He was admitted for surgery. We considered minimally invasive operation would be better for him and performed aortic valve replacement (Carpentier-Edwards Perimaunt valve 19 mm) by a right minithoracotomy approach because graft injury could occur by median sternotomy after CABG, and he had the risks of advanced age, low activities of daily living, and mild dementia. His postoperative course was uneventful. On echocardiography performed at postoperative days 9, the ejection fraction recovered to 75% from 53% before surgery and the mean aortic valve pressure gradient was 8 mmHg. He was discharged on postoperative day 12. Right minithoracotomy approach with port access is a good option for redo operation for aortic valve stenosis after CABG.

Prognostic facfors were examined in 71 patients receiving home oxygen therapy under the direction of our hospital between 1984 and 1994. In 25 patients who had undergone right catheterization, relationships between pulmonary hemodynamics and prognosis were also discussed. Mean pulmonary arterial pressure (P_PA) were correlated negatively with PaO₂. This indicated that hypoxic pulmonary vasoconstriction was the major cause of pulmonary hypertention in these patients. Pulmonary hypertention was revealed in 80% of the patients with P_PA ≥20 Torr and in 52% of the patients with P_PA ≥25 Torr. Acute hemodynamic effects of low-flow oxygen administration were investigated in 17 patients. PPA decreased significantly from 25.5 Torr to 23.5 Torr after oxygen administration and pulmonary arteriolar resistance (PAR) decreased from 243 dynes ·ses ·cm^-5 to 225 dynes·sec·cm^-5, but this change was not significant.
In patients with pulmonary fibrosis and sequelae of tuberculosis, the survival rates were lower than that of the patients with pulmonary emphysema. The median survival time (MST) for patients with cor pulmonale was significantly lower than that for those without cor pulmonale. When background factors were compared between the group with % home stay≥90% and % home stay<90%, there were no significant differences in observation periods, arterial blood gases and spirometry. The factors influencing % home stay were considered to be an important subject in addition to improving the survival rate.

The purpose of this study was to examine the effects of knee flexion angles during maximum isometric hip extension. Ten healthy men performed maximum isometric hip extension in prone position at 15° and 90° knee flexion. Then, the hip extension torque was measured, and electromyographic (EMG) data were obtained from the biceps femoris long head, semitendinosus, semimembranosus, adductor magnus, and gluteus maximus muscles. The EMG data were full-wave rectified and integrated (IEMG). The IEMG values obtained during the measurement of isometric hip extension were normalized with the values collected at 90° knee flexion (normalized IEMG [NIEMG]). The hip extension torque at 15° knee flexion was significantly greater than that at 90° knee flexion. The NIEMG values from the hamstrings at 15° knee flexion significantly increased compared with those at 90° knee flexion. Meanwhile, the NIEMG values from the gluteus maximus at 90° knee flexion were significantly greater than those at 15° knee flexion. However, the NIEMG values from the adductor magnus did not significantly differ between 15° and 90° knee flexion. These results indicate that the hamstrings effectively generate contracting force during isometric hip extension and at knee extended position because its fiber length was close to the optimal length.

In this study the effects of endurance exercise on cardiorespiratory functions and performance in developing age were exemined in 12 year old boys. Sujects were consisted of 11 boys who had been participating in training for soccer more than 2 hours a day for 6 days per week (S) and 10 non-participating boys for control (C) . Maximal oxygen uptake (Vo₂max), maximal heart rate (HRmax) and maximal cardiac output (Qmax) by acetylnerebreathing method were measured on the exercise on a treadmill. Five minute run was also administered.
Significant differences were found in Vo₂max (p<0.05), values of which were 2.13±0.07 1⋅min^-1 for S. and 1.86±0.08 1⋅min^-1 for C., respectively, and in Qmax (p<0.001), values of which were 17.9±1.41⋅min^-1 for S. and 12.4+0.71⋅min^-1 for C. G., respectively. There were no significant differences in HRmax and V_E between both groups. Values of stroke volume and V_E/Vo₂max were significantly higher for S.. Performances on 5 minute-run were 1164 m for S. and 1083 m for C, which showed significant difference (p<0.01) . Significant correlationship (r=0.746, p<0.001) was obtained between Vo₂max and Qmax. It was also found that the higher Vo₂max was, the higher Qmax was attaind.

Little is known about the effects of aerobic exercise on cardiac structure in children. Echocardiographic study was performed at rest in 38 boys aged 11-12 (18 soccer players and 20 untrained) . Soccer players had significantly increased left ventricular end-diastolic dimension (43.6±2.8 vs 40.1±2.8 mm) and left atrial dimension (27.7±3.7 vs 23.0±2.8 mm) . There was no difference in interventricular septum and left ventricular posterior wall thickness between the two groups, these data show that intensive aerobic exercise may influence on cardiac structure in children.