Graduation date: 2000

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