| Summary: | 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 �� 877��m��; Type II=2790 �� 756��m��). 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 ��m��, non-HRT: 3769 �� 912 ��m��) or Type II
fibers (HRT: 2770 �� 722 ��m��, non-HRT: 2849 �� 804 ��m��) 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. === Graduation date: 2003
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