ArticlesRandomised controlled trial of effect of high-impact exercise on selected risk factors for osteoporotic fractures
Introduction
Osteoporotic fractures in the elderly are a worldwide epidemic, and the predicted ageing of populations will accentuate the burden of these fractures on health-care systems.1 Balance, falling, the falling direction and mechanism, orientation of the faller, protective neuromuscular reflexes, local shock-absorbing capacity, and bone strength are factors associated with the risk of bone fractures due to falls.2, 3, 4, 5 The propensity to fall is also associated with muscle strength and power of the lower limbs.6, 7
In conjunction with the risk factors for falling, bone mineral density (BMD) is one of the most important determinants of fracture risk. BMD accounts for 80–90% of the variance in the strength of the proximal femur.8 The risk of hip fracture is approximately doubled for every 1 SD reduction in BMD.9 Epidemiological, clinical, and experimental exercise studies, in turn, indicate that physical activity is crucial in improving and maintaining bone mass and strength, thus helping to prevent osteoporotic fractures.10 Improved physical fitness is associated with better muscle strength, reaction time, balance, and coordination–all of which help to prevent falls and fall-induced fractures.7, 11, 12
Prevention of osteoporosis has targeted young and premenopausal women13 who are likely to be willing to participate in health-related physical activities. However, to our knowledge, no randomised trials of the effects of exercise on osteoporosis have been done among premenopausal women.
The purpose of this randomised intervention trial was to investigate whether an 18-month regimen of high-impact loading exercise would beneficially modify axial and lower-limb BMD, muscular performance, and dynamic balance in healthy premenopausal women. We used a high-impact regimen because a high magnitude of forces, high rate of force production, and exceptional loading directions and patterns are essential in maximising the skeletal adaptive response.14 This approach also allowed training of different movement skills and muscular performance, such as balance, coordination, muscle strength, and power.15
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Design and participants
Premenopausal women aged 35–45 years were recruited through a local newspaper advertisement for inclusion in a prospective, randomised controlled trial. Of the 242 women who responded, 140 were excluded after telephone interviews. The exclusion criteria were: cardiovascular, musculoskeletal, respiratory, or other chronic diseases that might limit training or testing; medication that could affect the skeleton; menstrual irregularities; special diet; smoking; obesity (body-mass index >30 kg/m2);
Results
39 women in the training group and 45 controls completed the study (figure 1). The other participants withdrew because of aggravation of previous musculoskeletal problems, pregnancy, accidental back injury, lower-limb overuse injury, loss of interest, or moving from the study area. During the study period, the trainees consulted the attending physician (PK) 16 times for the following reasons; mild ankle distortion (one), knee-overuse injuries (four), Achilles-tendon inflammation (one),
Discussion
In this study we have shown that high-impact exercise has a systematic, positive effect on the loaded axial and leg bones in conjunction with improvements in muscle power and dynamic balance. This exercise regimen was able to modify favourably multiple risk factors for osteoporosis and osteoporotic fractures, and proved to be feasible judged from the high attendance (80%), high compliance (83%), and the minimum need for medical services (16 visits over the entire study period).
Despite the
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