Resumen de Postmenopausal Effects of Resistance Training on Muscle Damage and Mitochondria
Thomas G. Manfredi, Michael A. Monteiro, Linda S. Lamont, Maria Fiatarone Singh, M. Foldvari, Sebrina White, Arthur C. Cosmas, Maria L. Urso
The purpose of this study was to measure the effects of a 12-month progressive resistance training intervention on muscle morphology and strength gains in postmenopausal women. Skeletal muscle biopsies were obtained from the vastus lateralis of 5 independent community-dwelling women (mean age: 75.6 ± 4.28 years; mean height: 163 ± 5.34 cm; mean weight: 72 ± 17.5 kg) before 6 months and 12 months after progressive resistance training. Muscle strength (1 repetition maximum) was measured at the same time points. After 6 months of training, morphological analysis revealed evidence of increased proteolysis and tissue repair, and rudimentary fiber development. The percent of Z-bands with mild Z-band disruption increased from 43.9% at baseline to 66.7% after 6 months of training (p < 0.01). Mitochondrial volume also increased (percent of mitochondria = 0.86% at baseline, 1.19% at 6 months, and 1.04% at 12 months, p < 0.05), and there was a shift to larger sized mitochondria. The training did not result in statistically significant increases in muscle leg strength (p < 0.18). It appears that mild Z-band disruption acts as a precursor for increased protein synthesis and stimulates an increase in mitochondrial mass. Therefore, although a progressive resistance training program in this population did not increase muscle strength, it did demonstrate clinical applications that lend support to the importance of resistance training in older adults.
