The effects of hormone replacement therapy on muscle strenght and morphology in early postmenopausal women Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8049g8752

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  • Postmenopausat women on hormone replacement therapy (HRT) have been reported to be stronger when compared to women who are not using HRT. The first goal of this study was to investigate whether muscle morphology was altered in women who use HRT when compared to women who do not use HAT. In addition, this study examined the combined effects of a 6-month moderate-intensity strength training (ST) routine and HRT on the neuromuscular system of early postmenopausal women. Because not all the women completed the ST, this study was separated into two separate analyses, baseline (n=17; 7 HRT, 10 non-HRT) and training (n=14; 6 HRT, 8 non-HRT). ST consisted of two exercises (squat and dead lift), two days a week, for 6-months. Vastus lateralis muscle biopsies were taken at baseline and 6-months after exercise training. Biopsy samples were sectioned and analyzed histochemically for muscle fiber type and fiber cross-sectional area (CSA). In addition, voluntary knee extension strength was assessed at 30°/sec using an isokinetic dynamometer at these two time points. At baseline there were no significant differences in knee extensor strength between groups (HRT: 443 ± 121 N, non-HRT: 490 ± 106 N). Regardless of hormone status, Type I fibers were significantly larger (p=.005) in GSA (Type I=3705 ± 877μm²; Type II=2790 ± 756μm²). However, there were significantly more Type II fibers (p<.0001) (61.5 ± 7.9% of total) and consequently, Type II fibers occupied significantly more total fiber area p=.00l2) (Type I=45.3 ± 7.4%; Type II=54.7 ± 7.4%). No significant differences were found in the fiber type distributions of the HAT (37.9 ± 2.5% Type I, 62.1 ± 2.5% Type II) and non-HRT (38.9 ± 2.9% Type I, 61.1 ± 2.9% Type II) groups. There were no significant differences in fiber CSA of Type I fibers (HRT: 3615 ± 886 μm², non-HRT: 3769 ± 912 μm²) or Type II fibers (HRT: 2770 ± 722 μm², non-HRT: 2849 ± 804 μm²) obtained from the two groups. Six months of ST had no effect on the strength, fiber CSA, and fiber type distribution for HRT and non-HRT subjects. These results suggest that HRT does not alter muscle strength, fiber type distribution, and fiber CSA in early postmenopausal women.
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  • description.provenance : Made available in DSpace on 2012-07-30T19:26:40Z (GMT). No. of bitstreams: 1 LewisDanielleR2003.pdf: 972238 bytes, checksum: 34a315d95e7630ec80883328149c1cae (MD5) Previous issue date: 2002-06-12
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