Control of human standing posture

我的NSERC资助的研究计划通过对运动单位行为的研究，研究大脑如何控制肌肉力量和运动，特别是在疲劳和姿势控制的条件下。运动单位是大脑发出的指令在肌肉中产生力量的手段。保持直立是人类活动的基础。站立平衡对于防止老年人跌倒的破坏性后果至关重要。小腿肌肉对站立平衡是必不可少的，以前人们认为所有的小腿肌肉在站立时都是统一激活的。传统上，肌肉激活是通过在肌肉中放置两个表面电极或细丝电极来测量的，但这些技术从相对较小的肌肉区域(毫米到厘米)的运动单位收集信息。我们将使用一种创新的方法来研究占据小腿肌肉不同区域的运动单位的数量。这是通过使用放置在整个肌肉上的20-24个非常小的电极(称为HDS-EMG)的网格来实现的。使用这项新技术，我们将研究肌肉对平衡障碍的反应方式是否存在重要的地区差异。我们将通过在受试者的臀部施加负荷来制造平衡障碍。将在不同的方向上施加不同大小的载荷(小腿肌肉疲劳和不疲劳)，以根据平衡障碍的特征确定小腿肌肉是否在特定区域被激活。年轻的健康受试者将与老年受试者进行比较，以确定区域激活是否有助于微调对平衡障碍的姿势反应，而老年人可能缺乏平衡障碍。最后，我们将探索大脑区域的激活与肌肉局部活动区域的关系，以确定在平衡障碍期间，大脑是否影响肌肉激活的模式。这些知识将促进我们对人体姿势控制的理解，并为老年人跌倒提供洞察力。

My NSERC-funded research program examines how the brain controls muscle force and movement, particularly under conditions of fatigue and postural control, through the study of motor unit behaviour. The motor unit is the means for the commands from the brain to create forces in the muscle. Maintenance of upright standing is fundamental to human mobility. Standing balance is of utmost importance to prevent the devastating consequences of falls in the aged. The calf muscles are essential for standing balance and previously all the calf muscles were thought to be activated uniformly in standing. Traditionally, muscle activation is measured with two surface electrodes or fine-wire electrodes placed in the muscle but these techniques collect information from motor units confined to a relatively small muscle region (mm to cm). We will use an innovative way of studying populations of motor units occupying different regions of the calf muscles. This is achieved by using grids of 20-24 very small electrodes (called HDS-EMG) placed over the entire muscle. Using this novel technology, we will examine whether there are important regional differences in how the muscles must react to balance disturbances. We will create balance disturbances by applying loads at the subjects' hips. Loads of varying magnitude will be applied in different directions (with and without fatiguing the calf muscles) to determine if the calf muscles are activated in specific regions based on the characteristics of the balance disturbance. Young healthy subjects will be compared to elderly subjects to determine if the regional activation serves to fine tune the postural response to the balance disturbance which may be lacking in the elderly. Finally, we will explore the relationship of activation of areas of the brain with areas of localized activity in the muscle to determine if the brain influences the pattern of muscle activation during balance disturbances. This knowledge will advance our understanding of human postural control and provide insight on falls in the elderly.