Tracy Brian L, Mehoudar Paul D, Ortega Justus D
Department of Health and Exercise Science, Colorado State University, 220 Moby-B Complex, Fort Collins, CO 80523-1582, USA.
Exp Brain Res. 2007 Jan;176(3):448-64. doi: 10.1007/s00221-006-0631-3. Epub 2006 Aug 4.
The purpose of this study was to determine motor output variability for different muscles in the same individuals. Ten young (21.7 +/- 3.4 years) and ten elderly (72.1 +/- 3.9 years) men underwent assessment of maximal isometric (MVC) and dynamic (1-RM) strength, and performed constant-force (2-50% MVC), constant-load (5-50% 1-RM load), and unloaded postural contractions as steadily as possible with the first dorsal interosseus (FDI), elbow flexors (EF), and knee extensors (KE). The coefficient of variation (CV) of force for isometric contractions and the standard deviation (SD) of acceleration for concentric, eccentric, and postural contractions were calculated. The 1-RM load, the CV of force for four of five isometric target forces, and the SD of acceleration during postural contractions were correlated between the EF and KE muscles. MVC force, 1-RM load, and SD of acceleration during postural contractions were not correlated between the FDI/EF or FDI/KE. The CV of force was correlated between the FDI/EF and FDI/KE for two of five isometric target forces. The SD of acceleration during concentric and eccentric contractions was not correlated between muscles. The normalized fluctuations during isometric contractions were greater for the FDI compared with the EF and KE. Elderly adults displayed greater fluctuations only for the FDI during low-force isometric and postural contractions. The dominant frequency of fluctuations was similar for the EF and KE muscles. The correlated fluctuations for the EF and KE muscles, within subjects, suggests that the two motor neuron pools transform the various neural inputs similarly.
本研究的目的是确定同一个体不同肌肉的运动输出变异性。十名年轻男性（21.7±3.4岁）和十名老年男性（72.1±3.9岁）接受了最大等长收缩（MVC）和动态收缩（1-RM）力量评估，并使用第一背侧骨间肌（FDI）、肘屈肌（EF）和膝伸肌（KE）尽可能稳定地进行恒力收缩（2-50%MVC）、恒负荷收缩（5-50%1-RM负荷）和无负荷姿势收缩。计算了等长收缩力的变异系数（CV）以及向心、离心和姿势收缩加速度的标准差（SD）。EF和KE肌肉之间，1-RM负荷、五个等长目标力中四个的力CV以及姿势收缩期间的加速度SD具有相关性。FDI/EF或FDI/KE之间，MVC力、1-RM负荷和姿势收缩期间的加速度SD无相关性。五个等长目标力中的两个，FDI/EF和FDI/KE之间的力CV具有相关性。不同肌肉之间，向心和离心收缩期间的加速度SD无相关性。与EF和KE相比，FDI等长收缩期间的标准化波动更大。老年人仅在低力等长和姿势收缩期间FDI的波动更大。EF和KE肌肉波动的主导频率相似。EF和KE肌肉在个体内的相关波动表明，两个运动神经元池对各种神经输入的转换方式相似。
