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Delaying Osteoporosis in Early Postmenopausal Women: Exercise as the New Medicine


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Delaying Osteoporosis in Early Postmenopausal Women: Exercise as the New Medicine

  1. 1. Delaying Osteoporosis in Early Postmenopausal Women: Exercise as the New Medicine<br />Stefanie E. Farr<br />Faculty of Health Sciences and Medicine Bond University, QLD 4229<br />Introduction:<br />As a condition that can be permanently disabling, there is little common education about the alternate therapies in the prevention, management and treatment of osteoporosis. Osteoporosis is a disease of the bone, characterized by a decrease in skeletal bone density1, which leads to an increased risk of fracture. In Australia, 2 in 5 women and 1 in 4 men over the age of 50 will experience an osteoporotic fracture2. <br />It has been observed in women of varying ethnicities that the fastest loss of bone mineral density occurs during the time of late perimenopause3, where the rate of bone loss is almost double in comparison to postmenopausal women4,5 (>5yrs post). The deterioration period between perimenopause and 5 years post-menopause has the greatest impact on bone strength3, and increases the propensity of fractures. It is estimated that 50% of all women over the age of 50 have osteopenia2: a decrease in bone mineral density, often a pre-cursor to osteoporosis.<br />There is no cure for osteoporosis, as there is a natural decline in bone mineral density with age. Prevention and management of age-related bone loss is important, particularly during the period of rapid bone loss observed during the early stages of post-menopause. A recent meta-analysis6 in early postmenopausal women participating in exercise in the form of a combined impact and high-magnitude resistance training (such as jogging, climbing stairs and walking) showed a positive effect on the preservation of bone mineral density. However, there is still discrepancies within the literature regarding the types of weight bearing exercise that are beneficial in preserving postmenopausal bone density.<br />Aims:<br />This report aims to differentiate between the forms of weight-bearing exercise, and determine the most beneficial in slowing the bone deterioration in the critical phase of menopause.<br />Methods:<br />Subjects:<br />48 postmenopausal women with osteoporosis completed this study (see Table 1 for baseline characteristics).<br />Intervention<br />All subjects acted as their own baselines and were assigned to a weight bearing exercise program over the duration of 2 years. Subjects were randomly assigned to a strength training (ST) or power-training (PT) group.<br />A progressive, periodised protocol was used, which was characterized by 12 week periods of high intensity training, interspersed with 4-5 weeks of lower training intensity, allowing for adaption and regeneration.<br />Note: the only difference between the strength training and power training groups is the speed in which the resistance exercises were performed.<br />Results:<br /><ul><li>Compared with the ST group, the PT group showed a 16% higher relative loading magnitude, a 82% higher relative loading amplitude, and a 262% faster loading rate (Figure 1)
  2. 2. Majority of ST group signal is in the 0-0.5 Hz range, whereas in the PT group there are high amplitudes from the 0-2.5 Hz range (Figure 2)
  3. 3. The ST group lost BMD and area significantly in the lumbar spine from baseline values (Table 4), and there were no differences in the PT group (Figure 3)
  4. 4. The ST group significantly lost BMD at the total hip and femoral neck from baseline (Table 3), however between groups there was no difference (Figure 3)</li></ul>Discussion:<br />Within this two-year exercise program in osteopenic post-menopausal women, differences between strength training (ST) and power training (PT) on bone mineral density were measured.<br />Significant variations in the loading stimuli (magnitude and rate) were seen between the PT group and the ST group (Figure 1). Previous studies10 found that the ground reaction forces were significantly related to the internal forces, and bone strain is directly proportional the applied force. A higher strain rate on the bone is associated with a larger adaptive bone growth response. Similarly, an increased loading frequency as seen in the PT group compared to the ST (Figure 2), has been suggested to be associated with higher osteogenic response11.<br />Compared to no loss in the PT group, the ST group had significant BMD loss in the lumbar spine after the 2-year period. The ST group also saw significant BMD loss in the proximal femur in comparison to the PT group. These results are consistent with the above findings, as the power training group experienced greater strain, initiating greater osteogenesis.<br />Conclusions:<br />This study concludes that long-term power training with high movement velocity is the superior form of weight training in maintaining bone mineral density in osteopenic postmenopausal women. <br />References:<br />Glaser, D. & Kaplan, F. 1997 “Osteoporosis: Definition and Clinical Presentation” Spine, vol. 22, issue 24, p. 12-16<br />Sambrook, PN. Seeman E. Phillips SR. & Ebeling PR. 2002 “Preventing osteoporosis: outcomes of the Australian Fracture Prevention Summit” The Medical Journal of Australia, vol. 176, issue 8, p. 1-16<br />Zaidi, M. et al. 2009 “Bone loss or lost bone: rationale and recommendations for the diagnosis and treatment of early postmenopausal bone loss” Current Osteoporosis Reports, vol. 7, issue 4, p. 118-126<br />Ho, SC. Et al. 2008 “Change in bone mineral density and its determinants in pre- and perimenopausal Chinese women: the Hong Kong Perimenopausal Women Osteoporosis Study” Osteoporosis International, vol. 19, issue 12, p. 1785-1796<br />Szejnfeld, V.L. 1994 “Bone density in white Brazilian women: Rapid loss at the time around the menopause” Calcified Tissue International, vol. 56, no. 3, p. 186-191<br />Martyn-St James, M. & Carroll, S. 2008 “A meta-analysis of impact exercise on post-menopausal bone loss: the case for mixed loading programmes” British Journal of Sports Medicine, vol. 43, p. 898-908<br />Torgerson, D. & Bell-Syer, S. 2001 “Hormone replacement therapy and prevention of vertebral fractures: a meta-analysis of randomised trials” BMC Musculoskeletal Disorders, vol. 2, issue 7<br />Shea, B. et al. 2001 “Meta-Analysis of Calcium Supplementation for the Prevention of Postmenopausal Osteoporosis” Endocrine Reviews, vol. 23, issue 4, p. 552-559<br />Von Stengel, S. et al. 2007 “Differential effects of strength versus power training on bone mineral density in postmenopausal women: a 2-year longitudinal study” British Journal of Sports Medicine, vol. 41, p. 649-655<br />Bassey, E.J. et al. 1997 “Relations between compressive axial forces in an instrumented massive femoral implant, ground reaction forces, and integrated electromyog-raphs from vastuslateralis during various “osteogenic” exercises” Journal of Biomechanics, vol. 30 p. 213-223<br />Turner, C.H. et al. 1994 “Mechanotransduction in bone: do bone cells act as sensors of fluid flow?” The Federation of American<br /> Societies for Experimental Biology Journal, vol. 8, p. 875-878<br />Table 4: Osteodensitometric and maximum muscle strength variables at baseline for subjects<br />Table 3: Exercise components in strength and power training groups<br />Figure 1: Force-time curves for strength-training (A) and power-training (B) groups<br />Figure 2: Contribution of the six 0.5 Hz frequency intervals to the total loading signal in the strength and power training groups<br />Figure 3: Percentage changes in bone mineral density (BMD) between baseline and yr 2 at the lumbar spine L1-L4 (A), the proximal femur (B) and the forearm (C) in the strength and power training groups<br />Table 1: Subjects anthropometric and nutritional data at baseline<br />Table 2: Exercise Interventions for Subject Groups<br />