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Histochemical and Enzymatic Comparison of the Gastrocnemius Muscle of Young and Elderly Men and Women
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1992
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The study examined how aging affects human skeletal muscle by comparing young (24 ± 1 yr) and older (64 ± 1 yr) men and women. Sedentary, nonsmoking adults were screened for disease, then lateral gastrocnemius biopsies were taken and analyzed with histochemical and biochemical techniques. Older adults had a higher proportion of type I fibers, smaller type IIa/IIb fibers, reduced capillarization, and lower mitochondrial enzyme activities, likely contributing to declines in muscle mass, strength, and endurance.
To examine the effects of aging on human skeletal muscle, 10 men and 10 women, 64 ± 1 yr old (Mean ± SE), and 10 men and 10 women, 24 ± 1 yr old, were studied. All subjects were sedentary nonsmokers who were carefully screened for latent cardiovascular, metabolic, or musculoskeletal disease. Needle biopsy samples were obtained from the lateral gastrocnemius muscle and examined using histochemical and biochemical techniques. The percentage of Type 1, Type IIa, and Type IIb fibers did not differ with age. However,Type I fibers occupied a larger percent of total muscle area in the older men and women (60.6 ± 2.6 vs 53.6 ± 2.0%; p < .05), because Type IIa and Type IIb fibers were 13–31% smaller (p < .001) in these subjects. Muscle capillarization and mitochondrial enzyme (i.e., succinate dehydrogenase, citrate synthase, and β-hydroxyacyl-CoA dehydrogenase) activities were also —25% lower (p < .001–.05) in the old subjects. Although it is difficult to determine whether these differences are due to aging itself or are simply due to inactivity, these structural and biochemical changes probably contribute to the decreases in muscle mass, strength, and endurance often observed in healthy but sedentary older men and women.