The purpose of this study was (1) to compare the lower body strength, power, and the bone mineral density (BMD) of the proximal femur in a group of trained postmenopausal women who have been in low intensity exercise program for a long time with age-matched sedentary controls, and (2) to evaluate the magnitude of the correlation between muscle function and site-specific BMD in these postmenopausal women. Healthy postmenopausal women (n = 17) between the age of 60 and 80 were divided into two groups: 9 exercisers (mean ± SE, 74.8 ± 3.2 years) who had been in an exercise training program for at least 5 years and 8 control (mean ± SE, 71.6 ± 3.4 years) who had not been in any exercise program for at least 5 years. The exercise group performed three one hour sessions a week of aerobic and resistance training for an average of 9.9 years. The exercise training consisted of 30 minutes walking and one or two sets of twelve to fifteen repetitions focused on large muscle groups. The BMD of the proximal femoral region was assessed using dual-energy x-ray absorptiometry (DEXA). By using a Cybex Leg Press machine, 1-repetition maximum (1-RM) tests were performed for lower body strength and power of lower body were obtained by a seated chair rise. Statistical analysis demonstrated no statistical differences between the left and right region of the femur BMD for either group, with the averaged BMD being 0.858 g/cm2 for the controls and 0.853 g/cm2 for the exercisers. The trochanter BMD for the exercisers were 7 % (left) and 6 % (right) higher than the controls although these values were not statistically significant. The 1RM leg press strength ranged from 29.5 to 47.6 kg (mean ± SE, 40.21 ± 2.62 kg) in controls and from 31.8 to 61.2 kg (mean ± SE, 45.93 ± 3.72 kg) in exercisers. Although the exerciser group lifted 14.2 % more weight than the control group, the difference was not statistically significant. The results of power test ranged from 14.59 to 31.21 kg • m/sec (mean ± SE, 22.94 ± 5.67 kg • m/sec) in controls and from 13.63 to 38.60 (mean ± SE, 28.88 ± 6.81 kg • m/sec). The power did not differ significantly between the two groups. However, it is noted that between group differences approached significance at p < 0.07. Correlations between body composition and femoral neck BMD were also determined. Neither weight, nor BMI was significantly correlated with femoral neck BMD in the exercise and control group. Lower body strength and power did not correlate with the BMD of the femoral neck, Ward's triangle, or trochanter in either group. Although the BMD of the proximal femoral region did not differ between two groups the higher mean age (+ 3.2 years) of the exercise group suggested that a low intensity exercise training program can increase power and strength and maintain BMD in postmenopausal women. However, the low intensity of resistance training program utilized by the exercise group was no more effective in maintaining BMD than an active lifestyle. / School of Physical Education

Studies in young women show that rowing exercise is osteogenic at the spine. However, little is known regarding rowing exercise and spine bone mineral density in older women. The aim of this study was to examine differences in spine bone mineral density (BMD) and back strength between premenopausal and postmenopausal competitive female masters rowers (n=28, 45.5 ± 4.7 yrs, n=28, 56.1 ± 5.7 years, respectively) and age-matched non-rowers (n=30, 43.3 ± 4.2 yrs; n=26, 56.8 ± 4.8 years). Competitive rowers were recruited from nine rowing clubs in the local area and compared to controls recruited from the same region who were normally active but not participating in rowing activity. Participating rowers had been engaged in competitive rowing for a minimum of one year. The average years spent rowing for the premenopausal and postmenopausal groups was 7.5 ± 6.6 yrs and 5.9 ± 6.9 yrs, respectively. BMD (g/cm²) of the third lumbar vertebrae (L3) was measured by dual-energy x-ray absorptiometry (DXA) in both the anterior-posterior and lateral views. Back strength was assessed using a standing cable tensiometer. Subjects also completed questionnaires to assess diet, physical activity, medical history and rowing history. Differences in BMD and back strength between groups were determined by analysis of covariance, controlling for lean mass. Compared to controls, postmenopausal rowers had 3.2% higher BMD at the anterior-posterior spine (p=.02) and 4.4% higher lateral spine BMD (p=.04). Furthermore, isometric back strength was 22.6% greater in these rowers than controls (p=.01). In contrast, controls had higher lateral BMD than rowers, with no differences in AP spine BMD or back strength between the premenopausal rowers and controls. Back strength was a significant predictor of AP spine BMD in premenopasual rowers and controls (R²=0.137, p=0.004) and of lateral spine BMD in postmenopausal rowers only (R²=0.153, p=0.04). There were no differences in calcium intake, age, menopausal status, weight, or lean mass between rowers and controls in either the premenopausal or postmenopausal samples. Since both increased BMD and back strength are associated with reductions in vertebral fracture risk, our results suggest that rowing exercise may be an important strategy to promote bone health and reduce vertebral fracture risk in postmenopausal women. However, the forces applied in rowing may not be great enough to alter bone mass before the onset of menopause. Therefore more research is needed examining rowing exercise in these older populations. / Graduation date: 2005

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