| Research Abstract |
Study 1 : The experimental study for the explication of mechanism on the joint contracture
Immobilization is often associated with a decrease in muscle elasticity. This condition is called muscle contracture, but the mechanism is not yet clear. We examined changes in ankle joint mobility, passive tension, sarcomere length, collagen fibril arrangement in the endomysium, and hyaluronic acid in muscular tissue 1, 2, 4, 8, and 12 weeks after immobilization of rat soleus muscles in shortened position. Ankle joint mobility decreased with the duration of immobilization. Passive tension on immobilized muscles had increased. Sarcomere length had shortened 1 week after immobilization, but did not show further change 2, 4, 8, and 12 weeks after immobilization. Collagen fibril arrangement in the endomysium 1 and 2 weeks after immobilization was longitudinal to the axis of the muscle fibers, whereas 4, 8, and 12 weeks after immobilization it was circumferential.
Hyaluronic acid in muscular tissue had
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increased 1 week after immobilization but remained at the same level at weeks 2, 4, 8, and 12. Histochemically, hyaluronic acid in the endomysium of immobilized muscular tissue was stained more strongly and widely than that in the control tissue. Increased hyaluronic acid in muscular tissue may induce muscle stiffness, but the significance of how hyaluronic acid is related to the mechanism of muscle contracture was not clear. The findings suggest mat muscle contracture started 1 week after immobilization and increased with the length of immobilization. Consequently, muscle contracture is affected by the shortening muscle fibers during the early stage of immobilization, after which the collagen adapts by the fibril arrangement in the endomysium becoming more circumferential. This change in collagen fibril arrangement may cause advanced muscle contracture in the late stage of immobilization.
Study 2 : The experimental study for the explication of therapy on the joint contracture
1) To determine whether prolonged stretching is preventing for joint contracture in mice. It was found that progression of joint contracture can not be prevented in periods of stretch lasting 10 min, and can prevent 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.
2) To determine whether prolonged stretching is ameliorating for disuse muscle atrophy in immobilized rat soleus muscles. Eighteen male Wistar rats were divided randomly into control (n=3) and immobilization (n=15) groups. The immobilization groups rats were immobilized on ankle joint for 4 weeks, animals were divided into three groups : immobilization alone (group I, n=3), stretch training for 30 min/day for 1or 3 weeks after remobilization (group S, n=6), and spontaneous recovery (non stretch training) for 1 or 3 weeks after remobilization (group NS, n=6). After 1 week of remobilization, muscle fiber diameters for type I fibers in group S had increased significantly compared with group NS. After 3 weeks of remobilization, muscle fiber diameters for types I and II fibers in group S had increased significantly compared with group NS. Our findings suggest that prolonged stretching induces recovery from disuse muscle atrophy after joint contracture. Less
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