Department of Biology of Physical Activity, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland.
Scand J Med Sci Sports. 2012 Jun;22(3):418-29. doi: 10.1111/j.1600-0838.2010.01228.x. Epub 2010 Oct 25.
Morphological evidence suggests that fast-twitch fibers are prone to disruption of their membrane structures by eccentric exercise. However, it is unclear how this is reflected in the discharge rate and action potential propagation of individual motor units, especially at high contraction levels. High-density surface electromyograms were recorded from biceps brachii muscle and decomposed to individual motor unit action potentials at isometric contraction levels between 10% and 75% of maximal voluntary contraction (MVC) before intermittent maximal elbow flexor eccentric exercise, and two hours (2H), two days (2D) and four days (4D) post-exercise. Maximal voluntary force decreased by 21.3±5.6% 2H and by 12.6±11.1% 2D post-exercise. Motor unit discharge rate increased and mean muscle fiber conduction velocity decreased, at the highest isometric contraction levels only (50% and 75% of MVC) at 2H post-exercise. These results indicate that eccentric exercise can disturb the function of motor units active at high contraction levels in the early stages after exercise, which seems to be compensated by the central nervous system with an increase in neural drive during submaximal isometric contractions.
形态学证据表明，快肌纤维容易因离心运动而破坏其膜结构。然而，目前尚不清楚这在个体运动单位的放电率和动作电位传播中是如何反映的，尤其是在高收缩水平下。在间歇性最大肘屈肌离心运动之前，在等长收缩水平下（最大自主收缩的 10%到 75%之间），从肱二头肌记录高密度表面肌电图，并将其分解为个体运动单位动作电位，运动后 2 小时（2H）、2 天（2D）和 4 天（4D）。最大自主力在 2H 后下降了 21.3±5.6%，在 2D 后下降了 12.6±11.1%。仅在 2H 后，最高等长收缩水平（MVC 的 50%和 75%）时，运动单位放电率增加，平均肌纤维传导速度降低。这些结果表明，离心运动可以在运动后早期干扰高收缩水平下活动的运动单位的功能，这似乎通过中枢神经系统在次最大等长收缩期间增加神经驱动来代偿。
