Craig C E, Goble D J, Doumas M
Department of Psychology, Queen's University Belfast, Belfast BT, UK.
School of Exercise & Nutritional Sciences, San Diego State University, San Diego 92101, USA.
Neuroscience. 2016 May 13;322:251-61. doi: 10.1016/j.neuroscience.2016.02.036. Epub 2016 Feb 22.
Older adults use a different muscle strategy to cope with postural instability, in which they 'co-contract' the muscles around the ankle joint. It has been suggested that this is a compensatory response to age-related proprioceptive decline however this view has never been assessed directly. The current study investigated the association between proprioceptive acuity and muscle co-contraction in older adults. We compared muscle activity, by recording surface electromyography (EMG) from the bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) muscles, in young (aged 18-34) and older adults (aged 65-82) during postural assessment on a fixed and sway-referenced surface at age-equivalent levels of sway. We performed correlations between muscle activity and proprioceptive acuity, which was assessed using an active contralateral matching task. Despite successfully inducing similar levels of sway in the two age groups, older adults still showed higher muscle co-contraction. A stepwise regression analysis showed that proprioceptive acuity measured using variable error was the best predictor of muscle co-contraction in older adults. However, despite suggestions from previous research, proprioceptive error and muscle co-contraction were negatively correlated in older adults, suggesting that better proprioceptive acuity predicts more co-contraction. Overall, these results suggest that although muscle co-contraction may be an age-specific strategy used by older adults, it is not to compensate for age-related proprioceptive deficits.
老年人采用不同的肌肉策略来应对姿势不稳，他们会使踝关节周围的肌肉“共同收缩”。有人认为这是对与年龄相关的本体感觉下降的一种代偿反应，然而这一观点从未得到直接评估。当前的研究调查了老年人本体感觉敏锐度与肌肉共同收缩之间的关联。我们通过记录双侧胫骨前肌（TA）和腓肠肌内侧头（GM）的表面肌电图（EMG）来比较年轻人（18 - 34岁）和老年人（65 - 82岁）在固定表面和以摇摆为参照的表面上进行姿势评估时的肌肉活动，评估时两个年龄组的摇摆程度相当。我们对肌肉活动和本体感觉敏锐度进行了相关性分析，本体感觉敏锐度通过主动对侧匹配任务进行评估。尽管成功地在两个年龄组中诱发了相似程度的摇摆，但老年人仍表现出更高的肌肉共同收缩。逐步回归分析表明，使用可变误差测量的本体感觉敏锐度是老年人肌肉共同收缩的最佳预测指标。然而，尽管先前的研究有相关暗示，但在老年人中本体感觉误差与肌肉共同收缩呈负相关，这表明更好的本体感觉敏锐度预示着更多的共同收缩。总体而言，这些结果表明，尽管肌肉共同收缩可能是老年人使用的一种特定于年龄的策略，但它并非用于补偿与年龄相关的本体感觉缺陷。
