Effects of Exercise and Physical Interventions on Bone: Clinical Studies - Skeletal Aging and Osteoporosis: Biomechanics and Mechanobiology - page 233

1 Physical Activity and Fracture Prevention
There is limited, but encouraging, evidence that physical activity reduces the
incidence of osteoporotic fractures. Solid evidence from randomized controlled
trials is lacking, but prospective cohort and case-control studies suggest that
physical activity is associated with reduced fracture risk.
1.1 Randomized Controlled Trials
There have been no large randomized controlled trials (RCT) to determine whether
an exercise intervention reduces the incidence of osteoporotic fractures. However,
two small RCTs that evaluated the effects of exercise on BMD and other osteo-
porosis risk factors conducted long-term follow-up evaluations of fracture inci-
dence in study participants [ 50 , 88 ]. Sinaki et al. randomized 50 postmenopausal
women to undergo 2 years of back strengthening exercise or no exercise and
evaluated the incidence of vertebral fractures 8 years after the completion of the
intervention [ 88 ]. There were 14 fractures among 322 vertebrae examined in
the control group (4.3%), compared with six fractures among 378 vertebrae in the
exercise group (1.6%; P = 0.03). Korpelainen et al. randomized 160 women aged
70-73 years to undergo 2.5 years of balance, leg strength, and impact exercises or
no exercise and evaluated the incidence of fractures after an average follow-up of
7 years [ 50 ]. The incident rate of any fracture was 0.05 per 1,000 person-years in
exercisers versus 0.08 per 1,000 person-years in controls [incidence rate ratio,
0.68; 95% confidence interval (CI), 0.34-1.32]. There were no hip fractures among
women in the exercise group and five among controls (P = 0.02). Because neither
of these studies reported on falls, it is not clear whether the potential anti-fracture
benefit of exercise is related to improvements in bone strength and/or a reduction
in falls.
1.2 Prospective Cohort and Case-Control Studies
A systematic review of the association of physical activity with fracture risk was
conducted in 2008 for the development of the 2008 Physical Activity Guidelines
for Americans [ 74 ]. One of the major conclusions from that review was that there
is an inverse association of physical activity with fracture risk (i.e., increased
physical activity, reduced fracture risk), particularly for hip fractures.
Both spine and hip fractures are of high clinical concern because of the related
morbidity and mortality. Few studies have evaluated the association of physical
activity and vertebral fracture risk and results have been mixed [ 27 , 82 , 84 , 87 , 88 ],
possibly because such fractures are more difficult to diagnose than hip fractures