Abstract：
This cross-sectional study aims to elucidate the neural mechanisms underlying the control of knee extension forces in individuals with anterior cruciate ligament reconstructions (ACLR). Eleven soccer players with ACLR and nine control players performed unilateral isometric knee extensions at 10% and 30% of their maximum voluntary force (MVF). Simultaneous recordings of high-density surface electromyography (HDEMG) and force output were conducted for each lower limb, and HDEMG data from the vastus lateralis (VL) and vastus medialis (VM) muscles were decomposed into individual motor unit spike trains. Force steadiness was estimated using the coefficient of variation of force. An intramuscular coherence analysis was adopted to estimate the common synaptic input (CSI) converging to each muscle. A factor analysis was applied to investigate the neural strategies underlying the control of synergistic motor neuron clusters, referred to as motor unit modes. Force steadiness was similar between lower limbs. However, motor neurons innervating the VL on the reconstructed side received a lower proportion of CSI at low-frequency bandwidths (< 5 Hz) in comparison to unaffected lower limbs (P < 0.01). Furthermore, the reconstructed side demonstrated a higher proportion of motor units associated with the neural input common to the synergistic muscle, as compared to unaffected lower limbs (P < 0.01). These findings indicate that the VL muscle of reconstructed lower limbs contribute marginally to force steadiness and that a plastic rearrangement in synergistic clusters of motor units involved in the control of knee extension forces is evident following ACLR.
摘要：
这项横断面研究旨在阐明前交叉韧带重建（ACLR）个体控制膝关节伸展力的神经机制。11名具有ACLR的足球运动员和9名对照运动员以其最大自愿力量（MVF）的10％和30％进行了单侧等距膝盖伸展。同时记录每个下肢的高密度表面肌电图（HDEMG）和力输出，来自股外侧肌（VL）和股内侧肌（VM）的HDEMG数据被分解为单个运动单位尖峰序列。使用力的变异系数来估计力的稳定性。采用肌内相干性分析来估计会聚到每个肌肉的共同突触输入（CSI）。应用因子分析来研究协同运动神经元簇控制的基础神经策略，称为电机单元模式。下肢之间的力稳定性相似。然而,与未受影响的下肢相比，在重建侧支配VL的运动神经元在低频带宽（<5Hz）下接收的CSI比例较低（P<0.01）。此外，重建的一侧表现出与协同肌肉常见的神经输入相关的运动单位比例较高，与未受影响的下肢相比（P<0.01）。这些发现表明，重建下肢的VL肌肉对力的稳定性贡献不大，并且在ACLR后，参与控制膝盖伸展力的运动单元协同簇的塑性重排很明显。
