Aging of skeletal muscle: a 12-yr longitudinal study

Author:

Frontera Walter R.12,Hughes Virginia A.2,Fielding Roger A.23,Fiatarone Maria A.24,Evans William J.5,Roubenoff Ronenn2

Affiliation:

1. Department of Physical Medicine and Rehabilitation, Harvard Medical School and Spaulding Rehabilitation Hospital, Boston 02114;

2. Nutrition, Exercise Physiology, and Sarcopenia Laboratory, Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Medford 02155;

3. Department of Health Sciences, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, Massachusetts 02215;

4. School of Exercise and Sport Science, University of Sydney, Sydney, New South Wales 2006, Australia; and

5. Donald W. Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72204

Abstract

The present study examines age-related changes in skeletal muscle size and function after 12 yr. Twelve healthy sedentary men were studied in 1985–86 (T1) and nine (initial mean age 65.4 ± 4.2 yr) were reevaluated in 1997–98 (T2). Isokinetic muscle strength of the knee and elbow extensors and flexors showed losses ( P < 0.05) ranging from 20 to 30% at slow and fast angular velocities. Computerized tomography ( n = 7) showed reductions ( P < 0.05) in the cross-sectional area (CSA) of the thigh (12.5%), all thigh muscles (14.7%), quadriceps femoris muscle (16.1%), and flexor muscles (14.9%). Analysis of covariance showed that strength at T1 and changes in CSA were independent predictors of strength at T2. Muscle biopsies taken from vastus lateralis muscles ( n = 6) showed a reduction in percentage of type I fibers (T1 = 60% vs. T2 = 42%) with no change in mean area in either fiber type. The capillary-to-fiber ratio was significantly lower at T2 (1.39 vs. 1.08; P = 0.043). Our observations suggest that a quantitative loss in muscle CSA is a major contributor to the decrease in muscle strength seen with advancing age and, together with muscle strength at T1, accounts for 90% of the variability in strength at T2.

Publisher

American Physiological Society

Subject

Physiology (medical),Physiology

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