Faculty of Health & Life Sciences, Northumbria University, Newcastle upon Tyne, UK.
Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, South Africa.
Exp Physiol. 2020 Mar;105(3):419-426. doi: 10.1113/EP088204. Epub 2020 Feb 7.
What is the central question of this study? Are there age-related differences in corticospinal responses whilst passively changing muscle length? What is the main finding and its importance? In contrast to young, older adults exhibited no modulation of corticospinal excitability in tibialis anterior during passive ankle movement. These data show impaired sensorimotor response in older adults during length changes of tibialis anterior, thus contributing to our understanding of age-related changes in sensorimotor control.
Corticospinal responses have been shown to increase and decrease with passive muscle shortening and lengthening, respectively, as a result of changes in muscle spindle afferent feedback. The ageing sensory system is accompanied by a number of alterations that might influence the processing and integration of sensory information. Consequently, corticospinal excitability might be modulated differently whilst changing muscle length. In 10 older adults (66 ± 4 years), corticospinal responses (MEP/M ) were evoked in a static position, and during passive shortening and lengthening of soleus (SOL) and tibialis anterior (TA), and these data were compared to the re-analysed data pool of 18 younger adults (25 ± 4 years) published previously. Resting motor threshold was greater in SOL compared to TA (P < 0.001), but did not differ between young and older (P = 0.405). No differences were observed in MEP/M between the static position, passive shortening or lengthening in SOL (young: all 0.02 ± 0.01; older: 0.05 ± 0.04, 0.03 ± 0.02 and 0.04 ± 0.01, respectively; P = 0.298), and responses were not dependent on age (P = 0.090). Conversely, corticospinal responses in TA were modulated differently between the age groups (P = 0.002), with greater MEP/M during passive shortening (0.22 ± 0.12) compared to passive lengthening (0.13 ± 0.10) and static position (0.10 ± 0.05) in young (P < 0.001), but unchanged in older adults (0.19 ± 0.11, 0.22 ± 0.11 and 0.18 ± 0.07, respectively; P ≥ 0.867). The present experiment shows that length-dependent changes in corticospinal excitability in TA of the young are not evident in older adults. This suggests impaired sensorimotor response during muscle length changes in older age that might only be present in ankle flexors, but not extensors.
本研究的核心问题是什么？在被动改变肌肉长度时，皮质脊髓反应是否存在与年龄相关的差异？主要发现及其重要性是什么？与年轻人相比，老年人在前胫骨在被动踝关节运动期间，前胫骨的皮质脊髓兴奋性没有调节。这些数据表明，老年人在前胫骨长度变化期间存在感觉运动反应受损，从而有助于我们理解与年龄相关的感觉运动控制变化。
皮质脊髓反应随着肌肉牵张反射的缩短和延长而分别增加和减少，这是由于肌梭传入反馈的变化。随着年龄的增长，感觉系统会发生许多变化，这些变化可能会影响感觉信息的处理和整合。因此，改变肌肉长度时，皮质脊髓兴奋性可能会以不同的方式进行调节。在 10 名老年人（66 ± 4 岁）中，在前胫骨（TA）的静态位置、被动缩短和延长过程中诱发皮质脊髓反应（MEP/M），并将这些数据与之前重新分析的 18 名年轻人（25 ± 4 岁）的数据进行比较。与 TA 相比，在 SOL 中，静息运动阈值更大（P < 0.001），但在年轻人和老年人之间没有差异（P = 0.405）。在 SOL 的静态位置、被动缩短或延长过程中，MEP/M 之间没有差异（年轻人：均为 0.02 ± 0.01；老年人：0.05 ± 0.04、0.03 ± 0.02 和 0.04 ± 0.01，P = 0.298），且反应不受年龄影响（P = 0.090）。相反，TA 中的皮质脊髓反应在不同年龄组之间存在不同的调节（P = 0.002），与被动伸长相比，在年轻人中，被动缩短时的 MEP/M 更高（0.22 ± 0.12）（0.13 ± 0.10）和静态位置（0.10 ± 0.05）（P < 0.001），而老年人则没有变化（0.19 ± 0.11、0.22 ± 0.11 和 0.18 ± 0.07，分别为 P ≥ 0.867）。本实验表明，年轻人 TA 中依赖长度的皮质脊髓兴奋性变化在老年人中并不明显。这表明，在老年人中，肌肉长度变化时的感觉运动反应受损，这种情况可能仅存在于踝关节屈肌，而不存在于伸肌中。
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