Physiological recruitment of motor units by high-frequency electrical stimulation of afferent pathways
Physiological recruitment of motor units by high-frequency electrical stimulation of afferent pathways
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DOI：
10.1152/japplphysiol.00327.2014
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发表时间：
2015-02-01
影响因子：
3.3
通讯作者：
Farina, Dario
中科院分区：
文献类型：
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作者：
Dideriksen, Jakob L.;Muceli, Silvia;Farina, Dario
神经肌肉电刺激(NMES)通常用于康复，但电诱发肌肉激活在几个方面不同于随意肌肉收缩。这些差异导致了在使用NMES恢复肌肉功能方面的挑战。我们研究了使用低电流、高频神经刺激通过脊髓运动神经元(MN)池激活肌肉，以获得更自然的激活模式。使用一种新的刺激方案，在100赫兹的刺激脉冲序列中，通过表面肌电可靠地估计低水平收缩时对单个刺激的H反射反应。此外，通过肌内肌电分析传入刺激引起的单个运动单位募集。结果表明，与较低的刺激频率相比，100赫兹刺激可显著提高H反射反应。此外，使用100赫兹刺激的运动单位招募并不完全同步，这在经典的NMES中发生，而且不同运动单位的放电率不同，因为每个单位只有在特定数量的刺激后才被激活。这些观察背后最可能的机制是从Ia纤维到MN的阈值下兴奋性突触后电位的时间总和。这些发现和它们的解释也被一个真实的MN群体传入刺激模拟模型所验证。这些结果表明，所提出的刺激策略可能允许通过与生理条件相似的运动单位招募来产生相当程度的肌肉激活。
Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation, but electrically evoked muscle activation is in several ways different from voluntary muscle contractions. These differences lead to challenges in the use of NMES for restoring muscle function. We investigated the use of low-current, high-frequency nerve stimulation to activate the muscle via the spinal motoneuron (MN) pool to achieve more natural activation patterns. Using a novel stimulation protocol, the H-reflex responses to individual stimuli in a train of stimulation pulses at 100 Hz were reliably estimated with surface EMG during low-level contractions. Furthermore, single motor unit recruitment by afferent stimulation was analyzed with intramuscular EMG. The results showed that substantially elevated H-reflex responses were obtained during 100-Hz stimulation with respect to a lower stimulation frequency. Furthermore, motor unit recruitment using 100-Hz stimulation was not fully synchronized, as it occurs in classic NMES, and the discharge rates differed among motor units because each unit was activated only after a specific number of stimuli. The most likely mechanism behind these observations is the temporal summation of subthreshold excitatory postsynaptic potentials from Ia fibers to the MNs. These findings and their interpretation were also verified by a realistic simulation model of afferent stimulation of a MN population. These results suggest that the proposed stimulation strategy may allow generation of considerable levels of muscle activation by motor unit recruitment that resembles the physiological conditions.