Neuromuscular plasticity during and following 3 wk of human forearm cast immobilization
Neuromuscular plasticity during and following 3 wk of human forearm cast immobilization
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DOI：
10.1152/japplphysiol.90530.2008
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发表时间：
2008-09-01
影响因子：
3.3
通讯作者：
Hoffman, Richard L.
中科院分区：
文献类型：
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作者：
Clark, Brian C.;Issac, Lailah C.;Hoffman, Richard L.
肌肉活动的长期减少会导致神经肌肉特性的改变;然而，适应的时间过程尚未完全了解，许多具体的适应也尚未确定。本研究评估了固定期间和固定后3周神经肌肉特性适应的时间演变。我们利用涉及神经刺激和经颅磁刺激的技术组合来评估肌肉中枢激活的变化，沿着脊髓（H反射）和皮质脊髓兴奋性[即，运动诱发电位（MEP）振幅、安静期（SP）和收缩特性。制动诱导中枢激活缺陷（85 +/- 3至67 +/- 7%），在石膏取出后1周恢复至基线水平。桡侧腕屈肌MEP振幅在制动后第一周增加了两倍以上，并在整个制动期间和石膏取出后1周保持升高。此外，我们观察到与基线相比，石膏取出后1周SP延长（78.5 +/- 7.1至98.2 +/- 8.7 ms）。收缩特性也发生了改变，因为制动后诱发力松弛的速率较慢（-14.5 +/-1.4至11.3 +/-1.0%峰值力/ms），并且在石膏移除后1周保持抑制（-10.5 +/-0.8%峰值力/ms）。这些观察结果详细说明了与废用相关的皮质脊髓和收缩特性的适应性的时间过程，并说明了固定对人类神经肌肉系统的深远影响，这一点可以通过去除石膏后皮质脊髓兴奋性持续1周的改变来证明。
Prolonged reductions in muscle activity results in alterations in neuromuscular properties; however, the time course of adaptations is not fully understood, and many of the specific adaptations have not been identified. This study evaluated the temporal evolution of adaptations in neuromuscular properties during and following 3 wk of immobilization. We utilized a combination of techniques involving nerve stimulation and transcranial magnetic stimulation to assess changes in central activation of muscle, along with spinal (H reflex) and corticospinal excitability [i.e., motor- evoked potential (MEP) amplitude, silent period (SP)] and contractile properties in 10 healthy humans undergoing 3 wk of forearm immobilization and 9 control subjects. Immobilization induced deficits in central activation (85 +/- 3 to 67 +/- 7%) that returned to baseline levels 1 wk after cast removal. The flexor carpii radialis MEP amplitude increased greater than twofold after the first week of immobilization and remained elevated throughout immobilization and 1 wk after cast removal. Additionally, we observed a prolongation of the SP 1 wk after cast removal compared with baseline (78.5 +/- 7.1 to 98.2 +/- 8.7 ms). The contractile properties were also altered, since the rate of evoked force relaxation was slower following immobilization (-14.5 +/- 1.4 to -11.3 +/- 1.0% peak force/ms), and remained depressed 1 wk after cast removal (-10.5 +/- 0.8% peak force/ms). These observations detail the time course of adaptations in corticospinal and contractile properties associated with disuse and illustrate the profound effect of immobilization on the human neuromuscular system as evidenced by the alterations in corticospinal excitability persisting 1 wk following cast removal.