Graduate Program in Health and Rehabilitation Science, Western University, London, ON, Canada.
Faculty of Health Sciences, Western University, London, ON, Canada.
Gait Posture. 2022 May;94:26-31. doi: 10.1016/j.gaitpost.2022.02.024. Epub 2022 Feb 23.
Balance is an important determinant of physical function and falls risk. The ability to withstand external perturbations is important when walking on icy or uneven surfaces, whether the perturbations are bilateral or unilateral.
This study sought to determine the effect of unilateral and bilateral standing perturbations on leg muscle activity in healthy older adults.
Participants experienced unilateral and bilateral standing perturbations of the treadmill. Surface electromyography (EMG) from lower limb muscles was recorded unilaterally. EMG onset latency and root mean square (RMS) amplitude of the muscle bursts were calculated.
Older adults demonstrated a combined ankle/hip strategy, along with pre-activation and co-contraction of muscles in response to unilateral and bilateral stance perturbations. As well, older adults demonstrated higher levels of EMG, but no difference in the latency of burst onset, in bilateral than unilateral perturbation types.
When the stance limb was perturbed in the bilateral condition, the older adults responded with a Gastrocs EMG burst nearly 100% of the maximum EMG. The high level of EMG used, especially in the Gastrocs, during the bilateral perturbations may reduce the safety factor for falls in older adults. Older adults responded to the different perturbation demands by modulating EMG amplitude as opposed to the onset timing of EMG.
平衡是身体功能和跌倒风险的重要决定因素。在冰面或不平整表面行走时，无论是双侧还是单侧受到外部干扰，能够承受干扰的能力都很重要。
本研究旨在确定单侧和双侧站立干扰对健康老年人下肢肌肉活动的影响。
参与者在跑步机上经历单侧和双侧站立干扰。记录下肢肌肉的表面肌电图（EMG）。计算肌肉爆发的起始潜伏期和均方根（RMS）振幅。
老年人表现出踝关节/髋关节的联合策略，以及对单侧和双侧站立干扰的肌肉预激活和共同收缩。此外，与单侧干扰相比，老年人在双侧干扰时表现出更高水平的 EMG，但爆发起始潜伏期没有差异。
当在双侧条件下干扰站立肢体时，老年人的 Gastrocs EMG 爆发接近最大 EMG 的 100%。在双侧干扰时，老年人使用的高 EMG 水平，尤其是在 Gastrocs 中，可能会降低老年人跌倒的安全系数。老年人通过调节 EMG 幅度而不是 EMG 起始时间来应对不同的干扰需求。
