Possible different roles of exercise in preventing vertebral and hip fractures

Abstract

Dear Editor, In postmenopausal women, a recent 16-year follow-up analysis of the Erlangen Fitness and Osteoporosis Prevention Study (EFOPS) by Kemmler and colleagues [1] showed significantly fewer major osteoporotic fractures including vertebral and hip fractures in the exercise group compared to the control group (rate ratio 0.37, 95 % confidence interval 0.14 to 0.88, p = .027). This is important evidence demonstrating that longterm multipurpose exercise programs can reduce low-trauma fracture risk in older adults. Here, we would like to discuss possible different roles of exercise in preventing vertebral and hip fractures on the basis of skeletal adaptation to mechanical environment (Wolff's law) [2].There is no doubt that exercise is a useful nonpharmacologic approach for preventing fragility fractures [3,4], although it was recently pointed out that exercise was recommended by less than half of guidelines about the management of osteoporosis [5]. The EFOPS trial found that long-term multipurpose exercise programs continuously slowed the age-related bone loss in the lumbar spine and hip [1,6]. Increased mechanical loading from exercise can improve bone fragility according to Wolff's law, which is expected to prevent non-fall-related vertebral fracture. In contrast, however, the exercise-related improvement of skeletal fragility could not efficiently act to prevent fall-related non-vertebral fractures such as in the hip because bones adapt to mechanical environment associated with physical activity, as indicated for example by trabecular pattern in the hip (Singh index), but not to falls that result in the different direction of force.On the other hand, a number of studies have confirmed that exercise plays significant roles in preventing falls [7][8][9][10][11]; in the EFOPS trial, approximately half of low-trauma fractures resulted from falls [1]. The latest meta-analysis of the associations between measures of balance and lower-extremity muscle strength/power suggests that these components are independent of each other [12] and indeed combined resistance and balance-jumping exercise for 5 years effectively reduced injurious falls compared to resistance or balance-jumping exercise alone in older women [13]. However, fall prevention is a hard task in aged adults, especially older than 80 years, as highlighted by recent large randomized trials [14-16] and pharmacologic therapies of sarcopenia [17][18][19] are expected to enhance the effects of exercise on fall prevention. Nevertheless, not only falling but also bone fragility should be targeted to prevent hip fracture in elderly people.Finally, bones normally respond to the change in local mechanical environment at each skeletal site to maintain resultant elastic deformation (strain) of bone; increased or decreased bone strain from physical activity would induce bone gain or loss, respectively [2]. Consequently, an ideal strategy to improve skeletal fragility is developing an agent that has the effect of mechanical strain-related stimulus; such alternative dru...

Osteoporosis Therapy: Bone Modeling during Growth and Aging

“…High bone mass in patients with sclerostin deficiency is present throughout the skeleton, including non-weight-bearing regions, such as the face and skull (40), indicating that anti-sclerostin antibodies are not agents that decrease the mechanical strain threshold for bone modeling; treatment with an anti-sclerostin antibody is highly efficacious even under conditions with impaired physical activity (50–54), whereas enhancing skeletal response to physical activity cannot effectively improve bone fragility caused by reduced skeletal loading. Accordingly, treatment with an anti-sclerostin antibody is likely to strengthen the skeleton, without any specific direction in contrast to exercise, to prevent fall-related fractures such as in the hip (55). …”