Kerkman Jennifer N, Zandvoort Coen S, Daffertshofer Andreas, Dominici Nadia
Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Amsterdam Movement Science Institute (AMS) and Institute for Brain and Behaviour Amsterdam (iBBA), Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
Front Netw Physiol. 2022 Mar 24;2:844607. doi: 10.3389/fnetp.2022.844607. eCollection 2022.
New-borns can step when supported for about 70-80% of their own body weight. Gravity-related sensorimotor information might be an important factor in developing the ability to walk independently. We explored how body weight support alters motor control in toddlers during the first independent steps and in toddlers with about half a year of walking experience. Sixteen different typically developing children were assessed during (un)supported walking on a running treadmill. Electromyography of 18-24 bilateral leg and back muscles and vertical ground reaction forces were recorded. Strides were grouped into four levels of body weight support ranging from no (<10%), low (10-35%), medium (35-55%), and high (55-95%) support. We constructed muscle synergies and muscle networks and assessed differences between levels of support and between groups. In both groups, muscle activities could be described by four synergies. As expected, the mean activity decreased with body weight support around foot strikes. The younger first-steps group showed changes in the temporal pattern of the synergies when supported for more than 35% of their body weight. In this group, the muscle network was dense with several interlimb connections. Apparently, the ability to process gravity-related information is not fully developed at the onset of independent walking causing motor control to be fairly disperse. Synergy-specific sensitivity for unloading implies distinct neural mechanisms underlying (the emergence of) these synergies.
新生儿在被支撑起自身约70 - 80%体重时能够迈步。与重力相关的感觉运动信息可能是发展独立行走能力的一个重要因素。我们探究了体重支撑如何在幼儿首次独立行走时以及在有大约半年行走经验的幼儿中改变运动控制。在跑步跑步机上对16名发育正常的不同儿童进行了（无）支撑行走评估。记录了18 - 24块双侧腿部和背部肌肉的肌电图以及垂直地面反作用力。步幅被分为四个体重支撑水平，从无支撑（<10%）、低支撑（10 - 35%）、中支撑（35 - 55%）和高支撑（55 - 95%）。我们构建了肌肉协同作用和肌肉网络，并评估了支撑水平之间以及组间的差异。在两组中，肌肉活动都可以用四种协同作用来描述。正如预期的那样，在足部着地时，平均活动随着体重支撑而降低。较年幼的首次行走组在体重支撑超过其体重的35%时，协同作用的时间模式出现了变化。在这个组中，肌肉网络密集，有几个肢体间的连接。显然，在独立行走开始时，处理与重力相关信息的能力尚未完全发育，导致运动控制相当分散。协同作用对卸载的特定敏感性意味着这些协同作用（出现）背后存在不同的神经机制。
