The effect of the muscular training on joint laxity and muscle extensibility

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In general, the appropriate joint stiffness has been regarded to prevent injuries and improve physical activities. In this study, we aimed to elucidate the effects of the muscular training on joint laxity and muscle extensibility. At first, we developed the animal models to evaluate joint laxity. Then, we examined the effect of acute and chronic exercise. The obtained results are summarized as follows ;1.We firstly developed the device to evaluate the flexibility of rat ankle joint. This house-made2.By using our developed device, we found that adult rat ankle joint showed lower laxity in comparison to young rat as reported in human studies.3.We also found the gender differences in rat ankle joint laxity as reported in human studies. The gastrocnemius muscle extensibility and connectin isoform compositions also differed.4.A bout of lengthening contractions on rat gastrocnemius muscle tentatively decreased rat ankle joint flexibility and increased rat gastrocnemius extensibility. We also … More confirmed that the passive tension of the exposed gastocnemius was significantly higher than that of the non-treated control. The muscle wet weights were identical in both groups, suggesting that the absence of edema. Interestingly, this phenomenon was only seen in young rats.5.We investigated the effects of repeated eccentric exercise (20 days) for rat gastrocnemius muscle on ankle joint stiffness and titin (connectin) isoform composition. After the prolonged eccentric exercise, the wet weight of medial gastrocnemius muscle significantly increased. Myosin-ATPase staining showed a decrease in the percentage of type IIB fibers and an increase in the percentage of type IIA fibers. We found that the ankle joint stiffness was significantly smaller in eccentric-exercise group than in sham-operated isometoric trained group. Above all, we conclude that chronic eccentric exercise increase both muscular strength and joint laxity.We are now considering that the prolonged eccentric exercise posses peculiar and should be useful for conditioning and prevention for sport-related injuries. Less