IMPAIRMENT OF NEUROMUSCULAR PROPAGATION DURING HUMAN FATIGUING CONTRACTIONS AT SUBMAXIMAL FORCES
IMPAIRMENT OF NEUROMUSCULAR PROPAGATION DURING HUMAN FATIGUING CONTRACTIONS AT SUBMAXIMAL FORCES
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DOI：
10.1113/jphysiol.1993.sp019486
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发表时间：
1993-01-01
影响因子：
5.5
通讯作者：
ENOKA, RM
中科院分区：
文献类型：
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作者：
FUGLEVAND, AJ;ZACKOWSKI, KM;ENOKA, RM
1.本研究的目的是检查神经肌肉传播障碍对持续到耐力极限的等长肌力水平的依赖性。该任务涉及人类志愿者通过尽可能长时间地激活第一背侧骨间肌来维持食指的次最大外展力。在疲劳收缩过程中，通过增加运动单位活动（如肌电图（EMG）所示），将次极力维持在三个水平之一（最大值的20、35或65%）。尽管在疲劳收缩期间EMG增加，但是对于所有受试者，EMG显著小于在耐力极限下的最大值（最大值的19- 55%的缺陷）。这种缺陷与持续次极量力的水平呈负相关。最大自主收缩力和抽搐力在疲劳收缩后显著降低。与肌电图一样，维持低目标力的受试者的力减少程度最大。疲劳性收缩导致M波振幅下降12- 23%，M波持续时间增加33- 51%，M波面积无变化。M波振幅的下降是神经肌肉传播障碍的一个指标，在持续低靶力的受试者中下降最大。对于所有三组受试者，在疲劳收缩期间，EMG的平均功率频率降低了相似的量（50- 57%）。建立了一个模型，该模型代表了增强和削弱力的过程的相互作用，以解释在不同目标力下持续收缩后抽搐力的恢复。我们的结论是，当力持续在次最大值时，受试者所经历的疲劳确实涉及神经肌肉传播的损伤。这种损伤是在次最大、疲劳收缩期间限制肌肉兴奋的一个因素，并导致疲劳任务结束时力量能力减弱。
1. The purpose of the study was to examine the dependence of neuromuscular propagation impairment on the level of isometric force sustained to the endurance limit. The task involved human volunteers sustaining a submaximal abduction force with the index finger by activating the first dorsal interosseous muscle as long as possible.2. The submaximal force was sustained at one of three levels (20, 35 or 65 % of maximum) by increasing motor unit activity, as indicated by the electromyogram (EMG), during the fatiguing contraction. Although the EMG increased during the fatiguing contraction, the EMG was significantly less than maximum at the endurance limit for all subjects (deficit of 19-55 % of maximum). This deficit was inversely related to the level of the sustained submaximal force.3. The maximum voluntary contraction and twitch forces were significantly reduced following the fatiguing contraction. As with the EMG, the degree of force reduction was greatest for the subjects who sustained the low target forces.4. The fatiguing contraction caused a 12-23 % decline in M wave amplitude, a 33-51 % increase in M wave duration, and no change in M wave area. The decline in M wave amplitude, which is an index of neuromuscular propagation impairment, was greatest among the subjects who sustained the low target forces.5. The mean power frequency of the EMG decreased by a similar amount (50-57 %) during the fatiguing contraction for all three groups of subjects.6. A model representing the interaction of processes that enhance and impair force was developed to explain the recovery of twitch force following the sustained contractions at different target forces.7. We conclude that the fatigue experienced by a subject when force is sustained at a submaximal value does involve an impairment of neuromuscular propagation. This impairment is one factor that limits muscle excitation during a submaximal, fatiguing contraction and contributes to the diminished force capability by the end of the fatigue task.