Department of Exercise and Sport Sciences, University of Copenhagen, Panum Institute 18.5, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
J Physiol. 2010 Nov 15;588(Pt 22):4387-400. doi: 10.1113/jphysiol.2010.195735. Epub 2010 Sep 13.
Corticospinal drive has been shown to contribute significantly to the control of walking in adult human subjects. It is unknown to what extent functional change in this drive is important for maturation of gait in children. In adults, populations of motor units within a muscle show synchronized discharges during walking with pronounced coherence in the 15-50 Hz frequency band. This coherence has been shown to depend on cortical drive. Here, we investigated how this coherence changes with development. Forty-four healthy children aged 4-15 years participated in the study. Electromyographic activity (EMG) was recorded from pairs of electrodes placed over the right tibialis anterior (TA) muscle during static dorsiflexion and during walking on a treadmill (speed from 1.8 to 4.8 km h(-1)). A significant increase of coherence with increasing age was found in the 30-45 Hz frequency band (gamma) during walking and during static ankle dorsiflexion. A significant correlation with age was also found in the 15-25 Hz frequency band (beta) during static foot dorsiflexion. χ(2) analysis of differences of coherence between different age groups of children (4-6, 7-9, 10-12 and 13-15 years of age) revealed a significantly lower coherence in the gamma band for recordings during walking in children aged 4-6 years as compared to older children. Recordings during static dorsiflexion revealed significant differences in both the beta and gamma bands for children in the 4-6 and 7-9 years age groups as compared to the older age groups. A significant age-related decrease in step-to-step variability of toe position during the swing phase of walking was observed. This reduction in the step-to-step variability of gait was correlated with increased gamma band coherence during walking. We argue that this may reflect an increased ability to precisely control the ankle joint position with age, which may be contingent on maturation of corticospinal control of the foot dorsiflexor muscles.
皮质脊髓驱动已被证明对成人的步行控制有重要贡献。但目前尚不清楚这种驱动的功能变化对儿童步态成熟的重要程度。在成年人中，肌肉中的运动单位群体在行走时会显示出同步放电，在 15-50Hz 的频段内表现出明显的相干性。这种相干性已被证明依赖于皮质驱动。在这里，我们研究了这种相干性如何随发育而变化。44 名年龄在 4-15 岁的健康儿童参与了这项研究。在静态背屈和在跑步机上行走（速度从 1.8 到 4.8km/h）时，用电极对右胫骨前肌（TA）进行肌电图（EMG）记录。在行走和静态踝关节背屈时，发现随着年龄的增加，在 30-45Hz 频率带（γ）中相干性显著增加。在静态足部背屈时，在 15-25Hz 频率带（β）中也发现了与年龄的显著相关性。对不同年龄组（4-6、7-9、10-12 和 13-15 岁）儿童行走时记录的相干性差异进行 χ(2)分析，发现 4-6 岁儿童行走时γ带的相干性明显低于年龄较大的儿童。在 4-6 和 7-9 岁年龄组的儿童中，β和γ带的记录在静态背屈时都有显著差异，与年龄较大的年龄组相比。在行走的摆动阶段，观察到趾位的步长间变异性随年龄的显著降低。这种步态步长间变异性的减少与行走时γ带相干性的增加有关。我们认为，这可能反映出随着年龄的增长，踝关节位置的精确控制能力增强，这可能依赖于足部背屈肌皮质脊髓控制的成熟。
