Exercise and Bone Health

“I exercise, so I don’t have to worry about osteoporosis.”

The mechanics of running include a heel strike impact resulting in 3 to 4 times as much force as the body weight of the individual depending on speed (Heinonen, et al., 1996). For this reason, more injuries result from running or impact type fitness activity than non-weight bearing exercise.

This has forced many physicians to encourage low-impact, or non-weight bearing (such as cycling) type of exercise for older individuals (Hopkins, et al., 1990, Robinson, et al., 1998, Rector, et al., 2008), in order to prevent osteoporosis. The effort to lower the risk of exercise injuries by lowering the level of impact, or eliminating it altogether, has not been as effective as high impact loading, as the loading along the axis of a bone is so much lower with low or non impact type activity.

In 2008, a study was published comparing bone health in adult male recreational athletes, aged 20 to 59, belonging to two groups, one group being cyclists (non-weight bearing exercisers), the other group being runners, (weight-bearing exercisers) as the impact loads are beyond their body weight. Sixty-three percent of the cyclists had osteopenia of the spine or hip (determined by DXA scans), compared to only 19% in the running group.

Dual-energy X-ray absorptiometry (DEXA) assess...

Dual-energy X-ray absorptiometry (DXA) assessment of bone mineral density of the femoral neck (A) and the lumbar spine (B): Courtesy: Dr Caroline LEBRETON, CHU Raymond Poincaré, Garches, France. (Photo credit: Wikipedia)

“Cyclists were 7 times more likely to have osteopenia of the spine than runners, controlling for age, body weight, and bone-loading history. Based on the results of this study, current bone loading is an important determinant of whole-body and lumbar spine bone mass density. Therefore, bone-loading activity should be sustained during adulthood to maintain bone mass.” (Rector, et al., 2008)

Osteoporotic patients may decide to walk, play golf, play croquet, or even garden in order to be physically active and load the bones to increase their density. As shown above however, these activities may be unable to deliver the level of loading required to actually reverse the bone mass loss and encourage bone mass gain. Any modality of exercise that can deliver the largest amount of axial mechanical loading will yield the greatest benefit to the patient. Increases in bone mass density have been experienced in cases where the levels of impact loading on the human body has equaled multiples of body weight.

Sources:

Heinonen, A., Kannus, P., Sievanen, H., Oja, P., Pasanen, M., Rinne, Ma., Uusi-Rasi, K., & Vuori, I. (1996). Randomised controlled trial of effect of high-impact exercise on selected risk factors for osteoporotic fractures. UKK Institute for Health Promotion Research. Lancet 1996; 348 (9038): 1343-1347.

Hopkins, D., Murrah, B., Hoeger, W., & Rhodes, R. (1990). Effect of low-impact aerobic dance on the functional fitness of elderly women. The Gerontologist (1990) 30 (2): 189-192. doi: 10.1093/geront/30.2.189.

Rector, R.S., Rogers, R., Ruebel, M., & Hinton, P.S. (2008). Participation in road cycling vs. running is associated with lower bone mineral density in men. Metabolism Clinical and Experimental. February 2008. 57(2): 226- 32. ISSN: 0026-0495.

Robinson, R, Krzywicki, T., Almond, L., Al–Azzawi, F., Abrams, K., Iqbal, S., & Mayberry, J. (1998). Effect of a low-impact exercise program on bone mineral density in Crohn’s disease: A randomized controlled trial. Gastroenterology. 115:36-41.

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