Kent-Braun J A, Ng A V, Young K
Magnetic Resonance Unit, Department of Radiology, University of California, San Francisco, California 94121, USA.
J Appl Physiol (1985). 2000 Feb;88(2):662-8. doi: 10.1152/jappl.2000.88.2.662.
To examine the influences of age, gender, and habitual physical activity level on human skeletal muscle composition, we developed a relatively simple magnetic resonance imaging method for the quantitation of leg anterior compartment contractile and noncontractile content. We studied 23 young (11 women and 12 men, 26-44 yr old) and 21 older (10 women and 11 men, 65-83 yr old) healthy adults. Analysis was by two-factor (age, gender) ANOVA. Physical activity, quantitated by three-dimensional accelerometer worn about the waist for 1 wk, was not different between groups. Men had larger contractile and noncontractile cross-sectional areas (cm(2)) than women, with no gender effect on percent noncontractile area. Young subjects had larger contractile areas and smaller absolute (cm(2)) and relative (percent total) noncontractile areas than older subjects. There was a significant linear relationship between physical activity and percent noncontractile area in older (r = -0.68, P = 0.002) but not young subjects. These data demonstrate a more than twofold increase in the noncontractile content of locomotor muscles in older adults and provide novel support for physical activity as a modulator of this age-related change in muscle composition.
为了研究年龄、性别和习惯性身体活动水平对人体骨骼肌组成的影响，我们开发了一种相对简单的磁共振成像方法，用于定量腿部前侧肌群的收缩成分和非收缩成分。我们研究了23名年轻（11名女性和12名男性，年龄26 - 44岁）和21名年长（10名女性和11名男性，年龄65 - 83岁）的健康成年人。分析采用双因素（年龄、性别）方差分析。通过佩戴在腰部1周的三维加速度计对身体活动进行定量，两组之间没有差异。男性的收缩和非收缩横截面积（平方厘米）大于女性，非收缩面积百分比没有性别差异。年轻受试者的收缩面积较大，绝对（平方厘米）和相对（占总面积百分比）非收缩面积小于年长受试者。在年长受试者中，身体活动与非收缩面积百分比之间存在显著的线性关系（r = -0.68，P = 0.002），而在年轻受试者中则不存在。这些数据表明，老年人运动肌肉的非收缩成分增加了两倍多，并为身体活动作为这种与年龄相关的肌肉组成变化的调节因素提供了新的支持。
