Muscle fiber size and function in elderly humans: a longitudinal study
Muscle fiber size and function in elderly humans: a longitudinal study
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DOI：
10.1152/japplphysiol.90332.2008
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发表时间：
2008-08-01
影响因子：
3.3
通讯作者：
Fielding, Roger A.
中科院分区：
文献类型：
--
作者：
Frontera, Walter R.;Reid, Kieran F.;Fielding, Roger A.
横断面研究可能低估了与年龄相关的骨骼肌力量和质量的变化。这项纵向研究的目的是评估同一队列中12名老年人(平均年龄：研究开始71.1+/-5.4岁，研究结束80+/-5.3岁)的整体肌肉和单一肌肉纤维的变化，5名男性志愿者相隔8.9岁。在随访中，体重、体重指数和体力活动没有明显变化。用等速测力法评估的肌力和膝关节伸肌的整体肌肉比力在随访时显著降低。根据计算机断层扫描的评估，伴随着大腿前肌室横截面积的显著减少(5.7%)。肌肉组织化学显示纤维类型分布和纤维面积无明显变化。用化学方法剥皮的单个肌肉纤维(n=411)的实验表明，I型纤维的大小没有变化，但IIA纤维的直径增加了。观察到这两种纤维的最大力都有增加的趋势。最大无负荷缩短率无明显变化。总而言之，在整个肌肉水平发生显著变化的情况下，老年人的单一肌肉纤维收缩功能可能会得到保护。这表明，存活的纤维弥补了部分肌肉大小的缺陷，试图保持最佳的力量生成
Crosssectional studies are likely to underestimate age-related changes in skeletal muscle strength and mass. The purpose of this longitudinal study was to assess whole muscle and single muscle fiber alterations in the same cohort of 12 older (mean age: start of study 71.1 +/- 5.4 yr and end of study 80 +/- 5.3 yr) volunteers (5 men) evaluated 8.9 yr apart. No significant changes were noted at follow-up in body weight, body mass index, and physical activity. Muscle strength, evaluated using isokinetic dynamometry, and whole muscle specific force of the knee extensors were significantly lower at follow-up. This was accompanied by a significant reduction (5.7%) in cross-sectional area of the total anterior muscle compartment of the thigh as evaluated by computed tomography. Muscle histochemistry showed no significant changes in fiber type distribution or fiber area. Experiments with chemically skinned single muscle fibers (n = 411) demonstrated no change in type I fiber size but an increase in IIA fiber diameter. A trend toward an increase in maximal force in both fiber types was observed. Maximum unloaded shortening velocity did not change. In conclusion, single muscle fiber contractile function may be preserved in older humans in the presence of significant alterations at the whole muscle level. This suggests that surviving fibers compensate to partially correct muscle size deficits in an attempt to maintain optimal force-generating