ULTRASTRUCTURAL CHANGES IN SKELETAL MUSCLE OF POSTMENOPAUSAL WOMEN FOLLOWING TWELVE MONTHS OF AEROBIC EXERCISE AND PROGRESSIVE RESISTANCE TRAINING
Cosmas, A.C.1, Monteiro, M.2, Levesque2, S., Fiataroni-Singh3, M., Manfredi, T.G2.
1Allied Health Professions, University of Connecticut, Storrs,
CT., 2Exercise Science, University of Rhode Island, Kingston, RI, 3JM USDA Human Nutrition Research Center on Aging at Tufts University.
Sarcopenia, a decrease in skeletal muscle mass with age, is characterized by declines in strength, aerobic power and lean mass and by an increase in fat mass. These changes become especially prominent following menopause and are attributed, at least in part, to decreased estrogen levels in
postmenopausal women. The pathological consequences of these changes include a greater incidence of atherosclerosis, osteoporosis, hypertension and hyperinsulinemia. This study examined the effects of 12 months of resistance and aerobic training on strength and aerobic capacity in 80 healthy postmenopausal women. Biopsies were taken from the vastus lateralis muscles of 5 of the subjects prior to the initiation of training and at 6 and 12 months during training and were examined by electron microscopy. A number of morphologial alterations suggestive of the mechanisms of sarcopenia were evident. Intrafascicular regions containing small, angulated fibers with centrally displaced nuclei were conspicuous and
numerous lipofuscin inclusions indicative of apoptosis were observed in the tissues examined prior to the initiation of the training program. Z-band damage was assessed by stereology and increased from 43.9% prior to training to 66.7% following 6 months of training. Mitochondrial density increased from 0.86 prior to training to 1.19 at 6 months and 1.04 following 12 months of training. Although statistically not significant,
this transition in mitochondrial volume may represent an increase in the percentage of smaller, more optimum sized mitochondria compared to a greater proportional increase in muscle fiber mass as a result of training.
It is conceivable that mitochondria are able to undergo morphological adaptations according to the energy requirements of the cellular compartment where they are located. These results support suggest that muscle damage is a characteristic feature of tissue remodeling and the mechanisms of sarcopenia may be retarded by aerobic and progressive resistance training.
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