Tracy Brian L, Dinenno Devin V, Jorgensen Bjorn, Welsh Seth J
Department of Health and Exercise Science, Colorado State University, Fort Collins, CO 80523-1582, USA.
Med Sci Sports Exerc. 2007 Mar;39(3):469-79. doi: 10.1249/mss.0b013e31802d3ad3.
To determine the contribution of visuomotor correction to increased force fluctuations in the elbow flexor and knee extensor muscles of elderly adults.
Young (N = 22, 23 +/- 3 yr) and elderly (N = 23, 74 +/- 7 yr) adults performed constant-force contractions at target forces of 2.5, 30, and 65% MVC. Visual feedback was provided (6-8 s) and then removed (6-8 s). After removal of drift (< 0.5 Hz) from the force, the standard deviation (SD) and coefficient of variation (CV) of force were calculated from vision and no-vision data.
Maximal voluntary contraction (MVC) force was 19% lower for elbow flexors and 37% lower for knee extensors in elderly adults than in young adults. Overall, the CV of force was 27% greater in the vision condition compared with the no-vision condition. The CV of force for vision was greater for elderly adults than for young adults at the 2.5% MVC target force and lower at 30 and 65% MVC. For the 2.5% MVC target force, the decline in CV of force from vision to no vision was greater for elderly adults than for young adults. At 30 and 65% MVC, the decline was significant but similar for young and elderly adults. For elbow flexors, the change in power from vision to no vision was greater for 0- to 4-Hz (reduced power) and 8- to 12-Hz (increased power) frequencies for elderly adults compared with young adults.
Visuomotor correction contributed to force fluctuations in large proximal muscles. The contribution was greater for healthy elderly adults at low forces. Visuomotor processes thus contributed to the age-related increase in force fluctuations.
确定视觉运动校正对老年人肘部屈肌和膝部伸肌力量波动增加的影响。
年轻成年人（N = 22，23±3岁）和老年人（N = 23，74±7岁）在2.5%、30%和65%最大自主收缩（MVC）的目标力下进行等力收缩。提供视觉反馈（6 - 8秒），然后移除（6 - 8秒）。从力量中去除漂移（<0.5赫兹）后，根据有视觉和无视觉数据计算力量的标准差（SD）和变异系数（CV）。
老年人肘部屈肌的最大自主收缩（MVC）力量比年轻人低19%，膝部伸肌低37%。总体而言，与无视觉条件相比，有视觉条件下力量的CV大27%。在2.5%MVC目标力时，老年人有视觉时力量的CV比年轻人更大，在30%和65%MVC时则更低。对于2.5%MVC目标力，老年人从有视觉到无视觉时力量CV的下降比年轻人更大。在30%和65%MVC时，年轻人和老年人的下降均显著但相似。对于肘部屈肌，与年轻人相比，老年人在0至4赫兹（功率降低）和8至12赫兹（功率增加）频率下从有视觉到无视觉时功率的变化更大。
视觉运动校正导致大的近端肌肉力量波动。在低力量水平下，健康老年人的这种影响更大。因此，视觉运动过程导致了与年龄相关的力量波动增加。
