The purpose of this study was to determine whether prolonged stretching prevents joint contracture that has been followed by simulated bed rest in mice. Thirty-four male IcR mice (age, 8 weeks; weight, 34.6 ± 1.5 g) were divided randomly into control (n=7) and experimental (n=27) groups. In the experimental group, bilateral ankles of each mouse were fixed in full planter flexion with a non-elastic tape, and each mouse was raised with the hindlimbs unweighted for 2 weeks. Of six mice in the experimental group, bilateral ankles were immobilized throughout the 2 week experiment. Of the other mice of the experimental group, the tape of bilateral ankles was removed and the ankle flexor muscles were maximally stretched by dorsiflexing the ankle joint under anesthesia, for periods of 10 min (n=8), 20 min (n=7) or 30 min (n=6) per day, 5 days per week for 2 weeks. After experiments, each mouse was given an anesthetic and the range of movement of the ankle was measured with a goniometer. It was found that progression of joint contracture can not be prevented in periods of stretch lasting 10 min, and can be prevented in periods of stretch lasting 20 min or more. But the progression of joint contracture can not completely prevented in periods of stretch lasting 30 min.

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Regeneration of rat soleus muscles was examined after injury had been achieved by the rubber band compression on the left hindlimb. Changes in the distributions of myosin heavy chain (MHC) isoforms in single fibers as well as in whole muscles were electrophoretically followed for 3 to 35 days after injury. Regeneration evoked not only a pronounced increase in the relative protein concentration of fast type MHC isoforms, but also an appearance of MHCIId, MHCIIb and neonatal MHC isoforms that are not comprised in normal soleus muscles. A single fiber analysis showed an elevation in the normally rare hybrid fiber population 14 days after injury (i.e., fibers containing more than one MHC isoform). At that time, hybrid fibers amounted to almost 60% of the total fibers studied. The combinations of MHC isoforms in hybrid fibers varied, but none of them expressed slow type MHCI. On the other hand an appreciable number of single fibers conatained MHCI with various fast type MHC isoforms after 35 days. Previous studies demonstrated that, in normal muscles, type IIC fibers classified on the basis of a histochemical staining for myofibrillar actomyosin ATPase consisted of MHCI and MHCIIa in varying ratio. The results presented in this study suggest that type IIC fibers during regeneration may differ from those in normal muscles with regard to the distribution of MHC isoforms.

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The purpose of this study was to investigate the effects of hip angles in horizontal plane on the hip abductor force (HAF). Twelve healthy female volunteers (mean age: 20.8 ± 0.6 years, range: 20-22 years) participated in this study.
Subjects fixed their supine position with the hip joint rotated at the angle of maximum internal-rotation (INT-rot), neutralization (N-rot), and maximum external-rotation (EXT-rot) out 30°-40° hip flexion, and fixed their prone position with the hip joint rotated at the angle of INT-rot, N-rot, and EXT-rot on 0°-10° hip extension. The maximum isometric HAFs were measured in a neutral and those six positions.
The mean ± standard deviation values of HAFs were 7.3 ± 1.5 kg・m at INT-rot, 7.4 ± 1.3 kg・m at N-rot, and 5.7 ± 1.1 kg・m at EXT-rot in flexion, and 7.8 ± 1.5 kg・m at INT-rot, 7.9 ± 1.31 kg・m at N-rot, and 6.5 ± 1.1 kg・m at EXT-rot in extention. A multiple comparison procedure (Tukey's HSD) was used to test the statistical significance of the mean difference in HAFs between six angles. The HAF at EXT-rot in flexion was significantly lower than those at N-rot and INT-rot angles. The HAF at EXT-rot in extention was significantly lower than HAFs at N-rot and INT-rot in extention.
These results assume that hip abductor muscles do not work enough because a trochanter major with angle of anteversion lies more posteriad at Ext-rot position.

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Comparison of the electromyography fatigue patterns of quadriceps femoral muscles during open kinetic chain and closed kinetic chain has not been reported. The purpose of this study, therefore, was to investigate the effects of exercise posture on the electromyography fatigue patterns of quadriceps femoral muscles during isometric knee extension and one-legged standing. All measurements were performed on healthy male subjects. Surface electromyography was recorded during the contractions of the vastus medialis, rectus femoris and vastus lateralis muscles. The tasks were one-legged standing and continuous isometric knee extension maintained for 2 minutes. The values of the average electromyography and median power frequency during the tasks were then calculated. The results of this study indicated that the muscle activity of quadriceps was almost equal in the beginning of each task. During one-legged standing, the average electromyography of each muscle was not increased at the end of the task. However, during isometric knee extension, the average electromyography of each muscle was significantly increased at the end of the task. During isometric knee extension, the median power frequency of each muscle was significantly decreased, and that of rectus femoris during one-legged standing was significantly decreased. This results suggest that the muscle fatigue pattern of quadriceps femoral muscles is different between open kinetic chain and closed kinetic chain.

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We have demonstrated the effect on exercise tolerance by introducing muscle training for patients with valvular heart disease after cardiac surgery. Subjects were 36 patients who had underwent the elective cardiac surgery from February, 1999 to January, 2000 at our university hospital. They were followed up for six months after their surgery. Subjects were divided into two groups; Group C (aerobic exercise only) and Group M (aerobic exercise with muscle training). They were supervised their exercise training during the hospitalization, but not after discharge. Exercise tolerance was evaluated by cardiopulmonary exercise testing and muscular strength of the legs were measured by Hand Held Dynamometer (Power Track II TM). The muscular strength of Group C increased from 61.5 ± 25.0 to 69.2 ± 24.6 Nm and that of Group M increased from 64.3 ± 19.4 to 81.7 ± 20.1 Nm. The Group M seemed to be more successful to improve the muscular strength. These exercise manners have beneficial effects on both peak VO₂ and exercise time, while there were no significant differences between Groups C and M. These results suggest that leg muscle training for patients with valvular heart disease who had underwent cardiac surgery may exert no effect on the exercise tolerance, but, may have an effect on the strength of leg muscle. The improvement of muscular strength may be helpful to patients in their daily activities. Further investigations will be needed whether both active aerobic exercise training and muscle resistance training are effective as cardiac rehabilitation in patients who received cardiac surgery.

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[in Japanese]

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