title: Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women.
abstract: 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 histomorphometry. Muscle strength increased, on average (+/- SEM), by 59.4 +/- 7.9% and 41.5 +/- 7.9% for HI and LO, respectively, compared to 1.3 +/- 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 = 0.11). 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 -1.8 +/- 0.6%, respectively, while HI maintained BMD (+1.0 +/- 1.0%). 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.
authors.affiliation: Musculoskeletal Research Laboratory, Veterans Affairs Medical Center, Palo Alto, California, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Taaffe
authors.forename: L
authors.initials: L
authors.lastname: Pruitt
authors.forename: G
authors.initials: G
authors.lastname: Pyka
authors.forename: D
authors.initials: D
authors.lastname: Guido
authors.forename: R
authors.initials: R
authors.lastname: Marcus
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001823:Body Composition; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D013848:Thigh