高速 downhill running におけるラットヒラメ筋錘内筋線維型の動員様式

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To investigate the recruitment patterns of intrafusal muscle fibers in rat soleus (SOL) muscles during fast downhill running, the optical intensity of glycogen content of each fiber was estimated in PAS stained-sections, using histochemical procedures. A rest control group (n=6) and two groups for exercise (level running and downhill running, 6 rats each) were prepared. Rats in all groups were subjected to training (5 days per week) for four weeks. On the experiment day, the rats in the downhill running group (downhill G, 16% decline) ran on a motor-driven belt with a speed of 40m/min for four min. The rats in level running group (Level G, 0% incline) run on a motor-driven belt with the same speed and duration as the downhill G. Extrafusal and intrafusal fiber types were identified by myosin ATPase staining. The optical intensity of glycogen content of all extrafusal and intrafusal fiber types decreased significantly in both groups that exercised. In regards to the rate of optical intensity of glycogen depletion to control values, however, the decreased rate of type IIA fibers after downhill running was significantly higher than that of type I fibers. The rate of optical intensity of glycogen depletion of type I fibers in downhill G was lower than that of type I fibers in level G. In addition, bag_2 fibers showed the larger rate of optical intensity of glycogen depletion than those of bag_1 and chain fibers. The rate of optical intensity of glycogen depletion of bag_2 fibers in downhill G was higher significantly than that of bag_2 fibers in level G. However, the rate of optical intensity of glycogen depletion of chain fibers in downhill G was less than that of downhill G. This result indicates that during intense downhill running as type IIA fibers in SOL muscle are mainly utilized ; the importance of bag_2 fibers increase and the importance of chain fibers decreases.
2005-02-25

高速 downhill running におけるラットヒラメ筋錘内筋線維型の動員様式

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