Motor Control and Biomechanics Laboratory, Graduate School of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa 359-1192, Japan.
Muscle Nerve. 2011 Jun;43(6):851-8. doi: 10.1002/mus.21989. Epub 2011 Apr 12.
In human movements muscles lengthen and then shorten, or occasionally shorten and then lengthen, but it is unclear whether the nature of neural activation of the initial phase influences the neural state of the subsequent phase. We examined whether contraction history modulates spinal excitability in the healthy human soleus muscle.
Subjects performed six blocks of 10 repetitions of four muscle actions consisting of specific combinations of passive shortening (PAS), and passive lengthening (PAL), shortening contraction (SHO), and lengthening contraction (LEN); that is: (1) SHO+PAL; (2) PAS+LEN; (3) PAS+PAL; and (4) SHO+LEN.
Compared with baseline, the H-reflex increased in the block of 300-400 s after SHO+PAL and decreased in the block of 0-100 s after PAS+LEN and SHO+LEN.
Our results suggest that spinal excitability is potentiated during a muscle action preceded by muscle shortening, but it becomes depressed during a muscle action preceded by muscle lengthening.
在人体运动中，肌肉先拉长然后再缩短，或者偶尔先缩短然后再拉长，但目前尚不清楚初始阶段神经激活的性质是否会影响后续阶段的神经状态。我们研究了健康人比目鱼肌的收缩历史是否会调节脊髓兴奋性。
受试者进行了 6 组 10 次的 4 种肌肉动作，包括被动缩短（PAS）和被动拉长（PAL）、缩短收缩（SHO）和拉长收缩（LEN）的特定组合；即：（1）SHO+PAL；（2）PAS+LEN；（3）PAS+PAL；和（4）SHO+LEN。
与基线相比，SHO+PAL 后的 300-400 秒内 H 反射增加，而 PAS+LEN 和 SHO+LEN 后的 0-100 秒内 H 反射减少。
我们的结果表明，在前一次肌肉缩短动作后，脊髓兴奋性增强，但在前一次肌肉拉长动作后，脊髓兴奋性减弱。
