INFERENCE OF MOTOR UNIT RECRUITMENT ORDER IN VOLUNTARY AND ELECTRICALLY ELICITED CONTRACTIONS
INFERENCE OF MOTOR UNIT RECRUITMENT ORDER IN VOLUNTARY AND ELECTRICALLY ELICITED CONTRACTIONS
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DOI：
10.1152/jappl.1990.68.4.1657
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发表时间：
1990-04-01
影响因子：
3.3
通讯作者：
DE LUCA, CJ
中科院分区：
文献类型：
--
作者：
KNAFLITZ, M;MERLETTI, R;DE LUCA, CJ
在22名健康人的胫骨前肌上进行了32次实验，研究了表面肌电信号参数与随意收缩或电诱发收缩水平之间的关系。在最大自主收缩扭矩的20%和80%下进行收缩。使用两个水平的刺激电流，分别产生最大M波和M波Δ。最大值的30%。一个四杆电极探头被用来检测单和双差分信号，从平均和中值频率的功率谱和平均肌纤维传导速度估计。从自主收缩获得的测量结果显示收缩水平与传导速度和频谱参数之间呈正相关。传导速度增加了21.2 ±。随意收缩水平从最大值的20%增加到80%时，收缩率为10.9%。光谱参数增加了类似的金额。通过表面电极对肌肉运动点施加强直电刺激20 s。使用宽度为0.1 ms且频率为20、25、30、35和40 Hz的矩形电流脉冲。随着刺激水平的增加，观察到四种类型的行为：1）15个实验中两个频谱参数和传导速度均随刺激而增加，2）8个实验中两个频谱参数均随刺激而减少，传导速度均随刺激而增加，3）6个实验中两个频谱参数均随刺激而减少，（4）3次实验中两个频谱参数均增大，传导速度均减小。在72%的实验中，传导速度随着刺激电流的增加而增加，表明募集顺序与自主收缩相似，尽管在其他28%的情况下传导速度下降，表明募集顺序相反。与在神经的直接刺激中观察到的相反，在肌肉运动点的电刺激期间，运动单位通常不以大小的相反顺序被募集。这种差异可能是几何因素或轴突分支直径之间缺乏相关性和/或轴突分支直径与亲本运动神经元轴突直径之间缺乏相关性的结果。传导速度和频谱参数在相反方向上的变化可能是运动单位募集顺序和与肌肉内募集的运动单位的几何位置相关联的不同组织过滤函数的组合效应的结果。
The relationship between surface myoelectric signal parameters and the level of voluntary or electrically elicited contractions was studied in 32 experiments on the tibialis anterior muscle of 22 healthy human subjects. Contractions were performed at 20 and 80% of the maximum voluntary contraction torque. Two levels of stimulation current were used, yielding, respectively, a maximum M wave and an M wave .apprx. 30% of the maximum. A four-bar electrode probe was used to detect single- and double-differential signals from which mean and median frequency of the power spectrum and average muscle fiber conduction velocity were estimated. Measurements obtained from voluntary contractions showed a positive correlation between contraction levels and both conduction velocity and spectral parameters. Conduction velocity increased by 21.2 .+-. 10.9% when voluntary contraction level increased from 20 to 80% of the maximal value. Spectral parameters increased by similar amounts. Tetanic electrical stimulation was applied to a muscle motor point for 20 s via surface electrodes. Rectangular current pulses with 0.1-ms width and frequencies of 20, 25, 30, 35, and 40 Hz were used. Four types of behavior were observed with increasing stimulation level: 1) the two spectral parameters and conduction velocity both increased with stimulation in 15 experiments, 2) the two spectral parameters decreased and conduction velocity increased in 8 experiments, 3) the two spectral parameters and conduction velocity both decreased in 6 experiments, and 4) the two spectral parameters increased and conduction velocity decreased in 3 experiments. Conduction velocity increased with increasing stimulation current in 72% of the experiments, indicating a recruitment order similar to that of voluntary contractions, although it decreased in the other 28% of the cases, indicating a reverse order of recruitment. Contrary to what is observed in direct stimulation of nerves, motor units are not in general recruited in reverse order of size during electrical stimulation of a muscle motor point. This discrepancy may be the result of geometric factors or a lack of correlation between axonal branch diameter and or a lack of correlation between axonal branch diameter and the diameter of the parent motoneuron axon. Changes of conduction velocity and spectral parameters in opposite directions may be the result of the combined effect of the motor unit recruitment order and of the different tissue filtering function associated with the geometric location of the recruited motor units within the muscle.