Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
PLoS One. 2013;8(3):e59029. doi: 10.1371/journal.pone.0059029. Epub 2013 Mar 18.
This study investigated whether the modular control of changes in direction while running is influenced by perturbations to balance. Twenty-two healthy men performed 90° side-step unperturbed cutting manoeuvres while running (UPT) as well as manoeuvres perturbed at initial contact (PTB, 10 cm translation of a moveable force platform). Surface EMG activity from 16 muscles of the supporting limb and trunk, kinematics, and ground reaction forces were recorded. Motor modules composed by muscle weightings and their respective activation signals were extracted from the EMG signals by non-negative matrix factorization. Knee joint moments, co-contraction ratios and co-contraction indexes (hamstrings/quadriceps) and motor modules were compared between UPT and PTB. Five motor modules were enough to reconstruct UPT and PTB EMG activity (variance accounted for UPT = 92 ± 5%, PTB = 90 ± 6%). Moreover, higher similarities between muscle weightings from UPT and PTB (similarity = 0.83 ± 0.08) were observed in comparison to the similarities between the activation signals that drive the temporal properties of the motor modules (similarity = 0.71 ± 0.18). In addition, the reconstruction of PTB EMG from fixed muscle weightings from UPT resulted in higher reconstruction quality (82 ± 6%) when compared to reconstruction of PTB EMG from fixed activation signals from UPT (59 ± 11%). Perturbations at initial contact reduced knee abduction moments (7%), as well as co-contraction ratio (11%) and co-contraction index (12%) shortly after the perturbation onset. These changes in co-contraction ratio and co-contraction index were caused by a reduced activation of hamstrings that was also verified in the activation signals of the specific motor module related to initial contact. Our results suggested that perturbations to balance influence modular control of cutting manoeuvres, especially the temporal properties of muscle recruitment, due to altered afferent inputs to the motor patterns. Furthermore, reduced knee stability during perturbed events may be related to overall control of lower limb muscles.
本研究旨在探讨在跑步时改变方向的模块化控制是否受到平衡干扰的影响。22 名健康男性在跑步时进行了 90°侧步无干扰（UPT）和初始接触干扰（PTB，可移动力平台平移 10cm）的切割动作。记录了支撑肢和躯干的 16 块肌肉的表面肌电图活动、运动学和地面反作用力。通过非负矩阵分解从肌电图信号中提取由肌肉权重及其相应激活信号组成的运动模块。比较 UPT 和 PTB 之间的膝关节力矩、共同收缩比和共同收缩指数（腘绳肌/四头肌）以及运动模块。五个运动模块足以重建 UPT 和 PTB 的肌电图活动（UPT 的方差解释率为 92±5%，PTB 为 90±6%）。此外，与驱动运动模块时间特性的激活信号的相似性（相似性=0.71±0.18）相比，观察到 UPT 和 PTB 的肌肉权重之间的相似性更高（相似性=0.83±0.08）。此外，与从 UPT 的固定激活信号重建 PTB 肌电图相比，从 UPT 的固定肌肉权重重建 PTB 肌电图的重建质量更高（82±6%）。在初始接触处的干扰减少了膝关节外展力矩（7%），以及在干扰开始后不久的共同收缩比（11%）和共同收缩指数（12%）。共同收缩比和共同收缩指数的这些变化是由于对初始接触相关特定运动模块的激活信号进行验证的，腘绳肌的激活减少所致。我们的结果表明，平衡干扰会影响切割动作的模块化控制，尤其是肌肉募集的时间特性，这是由于运动模式的传入输入发生改变。此外，在受干扰的事件中，膝关节稳定性降低可能与下肢肌肉的整体控制有关。
