The Time-Varying Nature of Electromechanical Delay and Muscle Control Effectiveness in Response to Stimulation-Induced Fatigue
The Time-Varying Nature of Electromechanical Delay and Muscle Control Effectiveness in Response to Stimulation-Induced Fatigue
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DOI：
10.1109/tnsre.2016.2626471
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发表时间：
2017-09-01
影响因子：
4.9
通讯作者：
Dixon, Warren E.
中科院分区：
文献类型：
--
作者：
Downey, Ryan J.;Merad, Manelle;Dixon, Warren E.
神经肌肉电刺激（NMES）和功能性电刺激（FES）是常用的康复疗法。闭环NMES有望产生更准确的肢体控制，这可能会实现新的康复程序。然而，NMES/FES可以迅速使肌肉疲劳，这限制了潜在的治疗并提出了几个控制挑战。具体地，刺激强度-力关系随着肌肉疲劳而改变。此外，在施加刺激和肌肉力量产生之间的延迟响应，称为机电延迟（EMD），可能会随着疲劳而增加。本文量化了这些影响。具体而言，开环疲劳协议适用于身体健全的人股四头肌肌肉群在等长条件下，并记录所产生的扭矩。短脉冲序列被用来测量EMD与阈值法，而长持续时间的脉冲序列被用来诱导疲劳，测量EMD与互相关法，并构建招聘曲线。发现EMD随着疲劳而显著增加，并且控制有效性（即，募集曲线的线性斜率）随着疲劳而降低。这些实验的结果表明，通过考虑EMD是时变的，并通过考虑肌肉募集曲线是刺激输入的非线性时变函数，改善闭环NMES/FES控制开发的机会。
Neuromuscular electrical stimulation (NMES) and Functional Electrical Stimulation (FES) are commonly prescribed rehabilitative therapies. Closed-loop NMES holds the promise to yield more accurate limb control, which could enable new rehabilitative procedures. However, NMES/FES can rapidly fatigue muscle, which limits potential treatments and presents several control challenges. Specifically, the stimulation intensity-forcerelation changes as the muscle fatigues. Additionally, the delayed response between the application of stimulation and muscle force production, termed electromechanical delay (EMD), may increase with fatigue. This paper quantifies these effects. Specifically, open-loop fatiguing protocols were applied to the quadriceps femoris muscle group of able-bodied individuals under isometric conditions, and the resulting torque was recorded. Short pulse trains were used to measure EMD with a thresholding method while long duration pulse trains were used to induce fatigue, measure EMD with a cross correlation method, and construct recruitment curves. EMD was found to increase significantly with fatigue, and the control effectiveness (i.e., the linear slope of the recruitment curve) decreased with fatigue. Outcomes of these experiments indicate an opportunity for improved closed loop NMES/FES control development by considering EMD to be time-varying and by considering the muscle recruitment curve to be a nonlinear, time-varying function of the stimulation input.