Dideriksen Jakob L, Muceli Silvia, Dosen Strahinja, Laine Christopher M, Farina Dario
Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany.
Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
J Appl Physiol (1985). 2015 Feb 1;118(3):365-76. doi: 10.1152/japplphysiol.00327.2014. Epub 2014 Dec 4.
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.
神经肌肉电刺激（NMES）常用于康复治疗，但电诱发的肌肉激活在多个方面与自主肌肉收缩不同。这些差异给使用NMES恢复肌肉功能带来了挑战。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，以实现更自然的激活模式。采用一种新颖的刺激方案，在低强度收缩期间，利用表面肌电图可靠地估计了在100Hz刺激脉冲序列中对单个刺激的H反射反应。此外，用肌内肌电图分析了传入刺激引起的单个运动单位募集情况。结果表明，相对于较低的刺激频率，在100Hz刺激期间获得了显著升高的H反射反应。此外，使用100Hz刺激时运动单位的募集并不完全同步，这与传统NMES中的情况不同，并且不同运动单位的放电率也不同，因为每个单位仅在特定数量的刺激后才被激活。这些观察结果背后最可能的机制是从Ia纤维到运动神经元的阈下兴奋性突触后电位的时间总和。这些发现及其解释也通过运动神经元群体传入刺激的真实模拟模型得到了验证。这些结果表明，所提出的刺激策略可能通过类似于生理条件的运动单位募集来产生相当程度的肌肉激活。
