| Budget Amount *help |
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2005: ¥5,800,000 (Direct Cost: ¥5,800,000)
Fiscal Year 2004: ¥9,300,000 (Direct Cost: ¥9,300,000)
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| Research Abstract |
We have previously shown that low-intensity resistance training cause increases in muscular size and strength when combined with moderate vascular occlusion. Elucidating its mechanism likely contributes not only to understand the common mechanisms of exercise-induced muscular hypertrophy but also to develop new exercise methods with much reduced mechanical stress. For this purpose, we developed two types of exercise model (animal and human models). In the animal model, major veins from hindlimb muscles of the rats were surgically crush-occluded with a heated metal needle. The chronic restriction of venous blood flow for 2 weeks caused in hindlimb muscles increases in wet and dry weights and total protein content, except for the soleus muscle. In the plantaris muscle, muscle fibers of all types (types I, IIa and IIb/x) showed an increase in their cross-sectional area (CSA). In addition, transitions of muscle-fiber types directed towards faster subtypes were observed to occur. The concen
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trations of glycogen, lactate, nitric oxide (NO), HSP-72 and active form of hepatocyte growth factor (HGF) increased, whereas that of myostatin decreased. Expressions of NOS-1 increased, whereas that of IGF-I tended to increase without significance. In the human model, low-intensity resistance exercise for knee extensor muscles (30% of one-repetition maximum) was performed twice daily for 2 weeks. Even with such short period of training, increases in muscle cross-sectional area (by〜10%) and strength occurred, and analyses for biopsy samples (v.lateralis) were made in a well-matched condition. Both type I and II fibers showed hypertrophy, though type II fibers tended to show a larger increase in CSA. DNA microarray analysis showed that expressions of IGF-I/II, follistain-like peptide, caveolin and extracellular matrix-related proteins increased, whereas that of myostatin considerably decreased. The results suggest that reduced oxygen delivery during exercise plays an important part and affects the factors relating to the proliferation of muscle satellite cells. Less
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