Greater amount of visual information exacerbates force control in older adults during constant isometric contractions
Greater amount of visual information exacerbates force control in older adults during constant isometric contractions
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DOI：
10.1007/s00221-011-2777-x
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发表时间：
2011-09-01
影响因子：
2
通讯作者：
Christou, Evangelos A.
中科院分区：
文献类型：
--
作者：
Kennedy, Deanna M.;Christou, Evangelos A.
本研究的目的是比较在两种不同的力水平下，当视觉反馈的量变化时，年轻人和老年人的力控制和激动剂肌肉活动的调节。10名年轻人（25岁+/- A 4岁，5男5女）和10名老年人（71岁+/- A 5岁，4男6女）被要求准确地将其最大等距力的2%和30%的恒定目标力与食指外展相匹配。每次试验持续35 s，视觉反馈的数量通过在0.05、0.5和1.5A度的角度变化而变化。每个受试者在每个视角条件下进行三次试验。力的变异性被量化为力的标准差和变异系数。激动剂肌肉活动的调节被量化为从放置在第一背骨间肌上的两对双极电极记录的肌电信号的归一化功率谱密度。感兴趣的频带在5到100赫兹之间。在力控制和视觉反馈量的变化方面存在显著的年龄相关差异。年轻人的力CV不随视角的变化而变化，而老年人的力CV则增加。虽然老年人在0.05A度时的CV值与年轻人相似（5.95 +/- A 0.67比5.47 +/- A 0.5），但老年人在0.5A度时的CV值大于年轻人（8.49 +/- A 1.34比5.05 +/- A 0.5）和1.5A度时的CV值（8.23 +/- A 1.12比5.49 +/- A 0.6）。此外，激动剂肌肉活动的调节存在年龄相关差异。随着视角的增加，年轻人的肌电图信号的归一化功率从13 Hz增加到60 Hz，而老年人则没有。这些发现表明，大量的视觉信息可能不利于老年人对恒定等距收缩的控制，这种损害可能是由于他们无法有效调节激动肌的运动神经元池。
The purpose of this study was to compare control of force and modulation of agonist muscle activity of young and older adults when the amount of visual feedback was varied at two different force levels. Ten young adults (25 years +/- A 4 years, 5 men and 5 women) and ten older adults (71 years +/- A 5 years, 4 men and 6 women) were instructed to accurately match a constant target force at 2 and 30% of their maximal isometric force with abduction of the index finger. Each trial lasted 35 s, and the amount of visual feedback was varied by changing the visual angle at 0.05, 0.5, and 1.5A degrees. Each subject performed three trials for each visual angle condition. Force variability was quantified as the standard deviation and coefficient of variation (CV) of force. Modulation of the agonist muscle activity was quantified as the normalized power spectrum density of the EMG signal recorded from two pairs of bipolar electrodes placed on the first dorsal interosseus muscle. The frequency bands of interest were between 5 and 100 Hz. There were significant age-associated differences in force control with changes in the amount of visual feedback. The CV of force did not change with visual angle for young adults, whereas it increased for older adults. Although older adults exhibited similar CV of force to young adults at 0.05A degrees (5.95 +/- A 0.67 vs. 5.47 +/- A 0.5), older adults exhibited greater CV of force than young adults at 0.5A degrees (8.49 +/- A 1.34 vs. 5.05 +/- A 0.5) and 1.5A degrees (8.23 +/- A 1.12 vs. 5.49 +/- A 0.6). In addition, there were age-associated differences in the modulation of the agonist muscle activity. Young adults increased normalized power in the EMG signal from 13 to 60 Hz with an increase in visual angle, whereas older adults did not. These findings suggest that greater amount of visual information may be detrimental to the control of a constant isometric contraction in older adults, and this impairment may be due to their inability to effectively modulate the motor neuron pool of the agonist muscle.