短縮性および伸張性収縮速度制御時におけるヒト単ー運動単位の活動様式

概要

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The authors have investigated the possibility that alternative activation of motor units can be performed in velocity-controlled dynamic contraction of knee extensor muscle. This experiment was conducted under the conditions of isometric and that of isotonic (15, 35, 70, 105deg/sec) by the use of coil-shaped wire electrodes and an apparatus which was set to eliminate lower leg's weight using counter balance. The results were summarized as follows; 1) A significant decrease of threshold force of motor units was observed in post dynamic contraction. 2) Firing frequency of motor units was shown to be getting higher with increasing velocity of knee extension. 3) During voluntary concentric contraction, the recruitment order of motor units deviated from isometric condition while velocity and load were increasing. 4) In the concentric contraction, a motor unit which recruited later than that in the isometric condition showed lowered firing frequency with increasing velocity of knee extension. 5) In the eccentric condition at certain velocity, selective recruitments of high-threshold motor units were observed. With these results, it was found that all motor units did not always show consistent activation pattern in terms of excitability of motor units. It was suggested that task dependent motor units were recruited according to the difference of synaptic input organization to spinal a-motoneurons.
社団法人日本体育学会の論文
1996-03-10