Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women

SUMMARY. The effects of 52 weeks resistance training at one of two exercise intensities on thigh muscle strength, fiber cross-sectional area (CSA), and tissue composition were studied in healthy 65–79-year-old women. Subjects were assigned to either a control (CO), high-intensity (HI) or low-intensity (LO) training group. Exercise regimens consisted of three sets of leg press, knee extension, and knee flexion exercises, 3 days/week, at either 80% of one-repetition maximum (1-RM) for seven repetitions (HI) or 40% of 1-RM for 14 repetitions (LO). Dynamic muscle strength was evaluated by 1-RM, thigh lean tissue mass (LTM), fat mass, and bone mineral density (BMD, g/cm²) by dual energy X-ray absorptiometry, and fiber CSA of vastus lateralis m. by histomor-phometry. Muscle strength increased, on average (± SEM), by 59.4 ± 7.9% and 41.5±7.9% for HI and LO, respectively, compared to l.3 ± 4.8% in CO (P = 0.0001). Type I fiber CSA increased over time (P < 0.05) in both exercise groups, with a trend for increased type II area (HI, P = 0.06; LO, P = 011). There was no significant effect of either exercise program on thigh tissue composition, except for BMD at the 1/3 site (middle third of the femur), where LO and CO groups experienced a decline (P < 0.05) of -2.2 ± 0.5% and -l.8 ± 0.6%, respectively, while HI maintained BMD (+ l.0 ± l.0%). Both training programs produced significant gains in thigh muscle strength, which were associated with fiber hypertrophy, although these did not translate into appreciable alterations in thigh tissue composition.