1993 Fiscal Year Final Research Report Summary
Responses in human motor unit activities during movement.
| Project/Area Number |
03454537
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
体育学
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| Research Institution | National Institute of Fitness and Sports |
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Principal Investigator |
KURATA Hiroshi Nat'l Inst.Fit.& Sports, Phys.Ed., Prof., 体育学部, 教授 (80056895)
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| Co-Investigator(Kenkyū-buntansha) |
OGAWA Y. Jikeikai Med.Sch., Med., Assist.Assoc., 医学部, 助手 (70142479)
NISHIZONO H. Nat'l Inst.Fit.Sports, Phys.Ed., Assoc.Prof., 体育学部, 助教授 (10125338)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Motor unit / Recruitment / Threshold force / Firing frequency / Contractile properties / Movement loading |
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| Research Abstract |
In single human motor units of abductor digiti minimi(ADM) muscle, there were motor units with maximal firing frequency at 80Hz, and with force threshold at 63% MVC.In motor units of ADM, extensor digitorum(ED), deltoid(D) and lateral vastus(LV) muscles, relationship between twitch contraction time, twitch peak tension and force threshold were examined. Force threshold was inversely proportional to contraction time except D muscle. Peak tension was proportional to force threshold except ED muscle. Relation between peak tension and contraction time was different in each muscle. In motor units of LV muscle, force threshold and its standard deviation tended to decrease following static force exersions. During isokinetic movement of knee and ankle joint at various load and angular velocities, recruitment order of motor units at shortening contractions widely changed from that at isometric contractions due to increase in load and shortening velocities. The results imply the selective recruitment of motor units depending on angular velocities. Also, the results suggest that there are two kinds of motor units recruited. One hand depends on the angular velocities, and the other hand depends on the joint angles. In characteristics of motor unis in ADM muscle following isometric and isotonic contractions, twitch contraction time tended to increase in fast type motor units, and it tended to decrease in slow type motor units. Recruitment and derecruitment order of motor units were different in the conditions of contractions. Due to the measurement of firing patterns of motor units in ADM and first dorsal interosseus(FDI) muscles during voluntary contractions, force control mechanisms were able to solve artificially by electrical nerve stimulations.
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