Abstract：
Acute intermittent hypoxia (AIH) is an emerging technique for facilitating neural plasticity in individuals with chronic incomplete spinal cord injury (iSCI). A single sequence of AIH enhances hand grip strength and ankle plantarflexion torque, but underlying mechanisms are not yet clear. We sought to examine how AIH-induced changes in magnitude and spatial distribution of the electromyogram (EMG) of the biceps and triceps brachii contributes to improved strength. Seven individuals with iSCI visited the laboratory on two occasions, and received either AIH or Sham AIH intervention in a randomized order. AIH consisted of 15 brief (∼60s) periods of low oxygen (fraction of inspired O2 = 0.09) alternating with 60s of normoxia, whereas Sham AIH consisted of repeated exposures to normoxic air. High-density surface EMG of biceps and triceps brachii was recorded during maximal elbow flexion and extension. We then generated spatial maps which distinguished active muscle regions prior to and 60 min after AIH or Sham AIH. After an AIH sequence, elbow flexion and extension forces increased by 91.7 ± 88.4% and 51.7 ± 57.8% from baseline, respectively, whereas there was no difference after Sham AIH. Changes in strength were associated with an altered spatial distribution of EMG and increased root mean squared EMG amplitude in both biceps and triceps brachii muscles. These data suggest that altered motor unit activation profiles may underlie improved volitional strength after a single dose of AIH and warrant further investigation using single motor unit analysis techniques to further elucidate mechanisms of AIH-induced plasticity.
摘要：
急性间歇性缺氧（AIH）是一种新兴的技术，可促进慢性不完全性脊髓损伤（iSCI）患者的神经可塑性。AIH的单一序列增强了手的握力和踝关节的足底屈扭矩，但潜在的机制尚不清楚。我们试图研究AIH引起的肱二头肌和肱三头肌肌电图（EMG）的幅度和空间分布变化如何有助于提高强度。7名iSCI人士曾两次参观该实验室,并按随机顺序接受AIH或ShamAIH干预.AIH由15个短暂的（〜60s）低氧（吸入O2=0.09的分数）与60s的常氧交替组成，而假AIH包括反复暴露于常氧空气。在最大肘部屈曲和伸展期间，记录了肱二头肌和肱三头肌的高密度表面肌电图。然后，我们生成了空间图，可以区分AIH或ShamAIH之前和之后60分钟的活跃肌肉区域。在AIH序列之后，肘关节屈伸力较基线增加91.7±88.4%和51.7±57.8%,分别,而假AIH后没有差异。强度的变化与肱二头肌和肱三头肌中EMG的空间分布改变和均方根EMG幅度增加有关。这些数据表明，单剂量AIH后，改变的运动单位激活曲线可能是提高的意志力的基础，并需要使用单运动单位分析技术进行进一步研究，以进一步阐明AIH诱导的可塑性机制。
