Paquin James, Power Geoffrey A
Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada.
Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada.
J Electromyogr Kinesiol. 2018 Aug;41:109-115. doi: 10.1016/j.jelekin.2018.05.005. Epub 2018 May 28.
The influence of active lengthening (residual force enhancement: RFE) and shortening (force depression: FD) on the electromyography (EMG)-torque relationship was investigated by matching torque and activation at 20%, 40%, 60%, 80% and 100% maximal voluntary contraction (MVC). Sixteen males performed lengthening and shortening contractions of the dorsiflexors over 25° into an isometric steady-state. There was 5% greater torque, with no change in agonist EMG during the RFE condition as compared to the isometric condition. Sub-maximally, in the force enhanced state, there was less agonist EMG during the torque clamp at all intensities relative to isometric, and greater torque during the activation clamps relative to isometric was observed across all intensities except 20% MVC. During the FD state compared to isometric, there was less torque produced during MVC (∼15%) with no change in agonist EMG. Sub-maximally, in the FD state, there was greater agonist EMG during the torque clamp and less torque during the activation clamp relative to the isometric condition across all intensities. The EMG-torque relationship was bilinear for all contraction types but was shifted to the left and right for FD and RFE, respectively as compared with isometric, indicating altered neuromuscular activation strategies in the history-dependent states of RFE and FD.
通过在20%、40%、60%、80%和100%最大自主收缩（MVC）时匹配扭矩和激活程度，研究了主动延长（残余力增强：RFE）和缩短（力抑制：FD）对肌电图（EMG）-扭矩关系的影响。16名男性进行了背屈肌超过25°的延长和缩短收缩，直至达到等长稳态。与等长收缩状态相比，在RFE状态下，扭矩增加了5%，而激动剂EMG没有变化。在次最大收缩时，在力增强状态下，相对于等长收缩，在所有强度的扭矩钳制期间激动剂EMG较少，并且在除20%MVC外的所有强度下，相对于等长收缩，在激活钳制期间观察到更大的扭矩。与等长收缩相比，在FD状态下，MVC期间产生的扭矩减少（约15%），而激动剂EMG没有变化。在次最大收缩时，在FD状态下，相对于等长收缩状态，在所有强度下，扭矩钳制期间激动剂EMG更大，而激活钳制期间扭矩更小。所有收缩类型的EMG-扭矩关系均为双线性，但与等长收缩相比，FD和RFE的关系分别向左和向右移动，表明在RFE和FD的历史依赖性状态下神经肌肉激活策略发生了改变。
