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Abstract & Commentary
Brooke-wavell and colleagues in loughborough, United Kingdom, studied 84 women aged 60-70 who were at least five years postmenopausal and had been sedentary. The women were randomly assigned to a walking group and a control group. The walkers followed a 12-month program at a self-selected brisk pace and reached an average of 20 minutes duration per day. The degree of walking had a beneficial effect as measured by a decrease in body mass and an increase in maximum oxygen uptake. Bone mineral density was measured in the lumbar spine and calcaneus. A statistically significant improvement in bone density was achieved only in the calcaneus. Brooke-Wavell et al conclude that ordinary brisk walking effectively reduced bone loss compared to control subjects.
I have been engaged in a running dialogue with colleagues in the bone world regarding the benefits of ordinary walking on maintaining bone density and preventing osteoporosis. It has been my impression that ordinary walking has a minimal effect as documented by Cavanagh and Cann.1 For exercise to be effective, it must exert a load or a stress on bone, and this is especially true of the spine.2
This article from the United Kingdom has been used by my colleagues in the bone world to argue that ordinary walking does have a beneficial effect. It seems to me, however, that close analysis of this article does not support their argument. The only significant increase in bone density occurred in the calcaneus. Since this is the site subject to stress during walking, it’s logical that this increase in bone is the result of mechanical strain in response to walking. Most importantly, there was no statistically significant difference in the bone mineral density change in the lumbar spine, and there was no change in the femoral neck. The bone mineral density in the lumbar spine in the control group decreased by 0.5% over the year, and in the walkers, the bone mineral density in the lumbar spine increased by 0.6%. Although this did not achieve statistical significance, it is possible that over a longer period of time a difference would have emerged. Nevertheless, these data do not document a difference in the lumbar spine that is clinically important.
Having now supported my argument that ordinary walking has little effect on bone density unless weights are carried in the hands, it is still reasonable to expect walking to have an overall beneficial effect on the risk of fracture. Walking improves the cardiovascular status of patients and reduces body mass in a beneficial way. These changes, as well as the exercise itself, will improve balance and, in so doing, decrease the risk of falling. In a cross-sectional study, walking was associated with a reduced risk of hip fracture, even when adjusted for bone mineral density, indicating the importance of balance and the effect on falling.3
Walking is inexpensive, enjoyable, and carries with it little risk of injury. A beneficial effect on cardiovascular conditioning and protection against fractures when practiced over a long period of time are important reasons to continue to promote this form of exercise for our older patients.
1. Cavanagh, Cann. Bone 1988;9:201.
2. Dalsky, et al. Ann Intern Med 1988;108:824.
3. Cummings, et al. N Engl J Med 1995;332:767.