Motor unit dysregulation following 15 days of unilateral lower limb immobilisation
Motor unit dysregulation following 15 days of unilateral lower limb immobilisation
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单侧下肢固定 15 天后运动单位失调
DOI：
10.1101/2022.06.01.494421
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Inns T
中科院分区：
文献类型：
--
作者：
Inns T
摘要废用性萎缩是由肢体不动等非负荷情况引起的，与肌肉质量相比，骨骼肌功能迅速但分散地降低。虽然对质量损失的机械洞察得到了很好的研究，但肌肉功能的恶化，重点是肌肉的神经输入仍然没有得到充分的研究。本研究旨在确定运动单位适应在废用性神经肌肉缺陷中的作用。10名年轻健康男性志愿者接受了15天的单侧下肢固定，在废用前后，膝伸肌收缩正常化至最大随意收缩（MVC）期间，从股外侧肌（VL）记录双侧肌内肌电图（iEMG）。通过超声测定肌肉横截面积。对个体MU进行采样并分析运动单位（MU）放电和MU电位（MUP）特征的变化。VL CSA降低了约15%，固定肢体的肌力降低了2倍31%，而非固定肢体的两个参数均无变化。MUP大小的参数减少了11%至24%，而神经肌肉接头（NMJ）的传输不稳定性保持不变，MU放电率下降了8%至11%，在几个收缩水平。所有适应性变化仅在固定肢体中观察到。这些研究结果突出了神经输入受损后的固定反映了抑制MU发射率，这可能是支持的力量相对于肌肉大小不成比例的减少。关键点肌肉质量和功能下降迅速废用的情况下，如卧床休息和肢体固定。肌肉功能的减少通常超过肌肉质量，这可能与神经输入到肌肉的失调有关。我们用肌内肌电图从单侧肢体制动15天后的股外侧肌取样单个运动单位和近纤维电位。废用后，肌肉力量的不成比例的损失时，与大小相一致的抑制运动单位firing rate.These运动单位的适应观察到在多个收缩水平，并在固定的肢体。我们的研究结果表明，神经失调是人类肌肉废用后功能丧失的关键组成部分。
AbstractDisuse atrophy, caused by situations of unloading such as limb immobilisation, causes a rapid yet diverging reduction in skeletal muscle function when compared to muscle mass. While mechanistic insight into the loss of mass is well studied, deterioration of muscle function with a focus towards the neural input to muscle remains underexplored. This study aimed to determine the role of motor unit adaptation in disuse‐induced neuromuscular deficits. Ten young, healthy male volunteers underwent 15 days of unilateral lower limb immobilisation with intramuscular electromyography (iEMG) bilaterally recorded from the vastus lateralis (VL) during knee extensor contractions normalised to maximal voluntary contraction (MVC), pre and post disuse. Muscle cross‐sectional area was determined by ultrasound. Individual MUs were sampled and analysed for changes in motor unit (MU) discharge and MU potential (MUP) characteristics. VL CSA was reduced by approximately 15% which was exceeded by a two‐fold decrease of 31% in muscle strength in the immobilised limb, with no change in either parameter in the non‐immobilised limb. Parameters of MUP size were reduced by 11% to 24% with immobilisation, while neuromuscular junction (NMJ) transmission instability remained unchanged, and MU firing rate decreased by 8% to 11% at several contraction levels. All adaptations were observed in the immobilised limb only. These findings highlight impaired neural input following immobilisation reflected by suppressed MU firing rate which may underpin the disproportionate reductions of strength relative to muscle size.Key pointsMuscle mass and function decline rapidly in situations of disuse such as bed rest and limb immobilisation.The reduction in muscle function commonly exceeds that of muscle mass, which may be associated with the dysregulation of neural input to muscle.We have used intramuscular electromyography to sample individual motor unit and near fibre potentials from the vastus lateralis following 15 days of unilateral limb immobilisation. Following disuse, the disproportionate loss of muscle strength when compared to size coincided with suppressed motor unit firing rate.These motor unit adaptations were observed at multiple contraction levels and in the immobilised limb only. Our findings demonstrate neural dysregulation as a key component of functional loss following muscle disuse in humans.
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影响因子：
120.7
作者：
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通讯作者：
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影响因子：
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作者：
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DOI：
10.1016/j.biocel.2013.06.011
发表时间：
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