Exercise, Bone Disease and Chronic Kidney Disease

by Patricia Gordon, R.N., Ph.D

Disturbances in mineral and bone metabolism occur early in the course of chronic kidney disease (CKD). Without prevention or treatment these disturbances progress to renal osteodystrophy encompassing varying combinations and degrees of high- and low-turnover bone disorders.

Although a broad body of literature indicates that load-bearing exercise has favorable effects on bone metabolism in the adult and aged skeleton [1, 2], there are no studies on the impact of exercise on bone in chronic or end stage renal disease (ESRD). However, much of what is known regarding the effects of exercise on bone, particularly in osteoporosis, may be helpful in the preservation of bone strength in these populations. This may be especially relevant due to the contribution of age-associated osteoporosis as the average age of CKD and ESRD patients increases.

While high impact activity is especially osteogenic [3], moderate intensity walking results in modest increases in lumbar bone mineral density (BMD) [4], indicating that low-impact activities can have a beneficial effect. This is an important consideration for individuals with kidney disease since they are prone to fatigue and generally have low exercise capacity [5]. Further, renal osteodystrophy carries increased risk for spontaneous tendon rupture, and low impact exercise is a safer choice. In the walking study, BMD increased due to suppression of bone turnover. Though suppression of bone turnover may be a concern in low-turnover disease, a recent report shows that active ESRD patients with adynamic bone disease have greater mineralized bone volume due to minimodeling compared to less active patients [6]. This suggests that bone formation can continue on a limited basis via this process that appears to be enhanced by physical activity.

Studies in humans including hemodialysis patients [7] show a positive correlation between muscle strength and BMD. This is because mechanical loading applied to the bone by muscle is directly responsible for bone formation and remodeling [8]. Although the effects of strength training on BMD have been equivocal in healthy populations [2], strength and muscle mass do increase in response to strength training in ESRD [9], and thus may benefit bone.

While there is no direct information to support beneficial effects of exercise on the bone disorders in kidney disease, existing information is suggestive of such effects. Because the literature suggests that both low-impact weight bearing exercise such as walking and resistance exercise (strength training) are beneficial to bone, patients with kidney disease should be encouraged to find ways to add these types of physical activity to their daily life. Easy suggestions to encourage more walking include; finding a walking buddy to take walks in the neighborhood, walking the dog, joining a local mall walking program, walking up a flight of stairs instead of taking the elevator, and parking the car further from the store. Local community centers often offer low impact exercise classes, and low to moderate intensity resistance exercise classes, as do many gyms. There are two very good illustrated resistance exercise program guides that patients can download from the National Institute of Aging (www.niapublications.org/exercisebook/index.asp) and from Life Options (www.lifeoptions.org ), another organization that helps educate people with CKD. The NKF also has good information about exercise for people with CKD on its Web site, www.kidney.org. Finally, the overall benefit of physical activity in decreasing the risks of comorbidities and preserving physical function cannot be overlooked, and the recommendation and encouragement of physical activity should be a priority for this population; see www.imakenews.com/ckdupdate/e_article000466465.cfm?x=b11,0,w .

Reference:

1. Wolff I, van Croonenborg JJ, Kemper HCG, Kostense PJ, Twisk JWR: The Effect of Exercise Training Programs on Bone Mass: A Meta-analysis of Published Controlled Trials in Pre- and Postmenopausal Women. Osteoporosis International 9:1-12, 1999
2. Wallace BA, Cumming RG: Systematic Review of Randomized Trials of the Effect of Exercise on Bone Mass in Pre- and Postmenopausal Women. Calcified Tissue International 67:10-18, 2000
3. Heinonen A, Oja P, Kannus P, Sievanen H, Haapasalo H, Manttari A, Vuori I: Bone mineral density in female athletes respresenting sports with different loading characteristics. Bone 17:197-203, 1995
4. Yamazaki S, Ichimura S, Iwamoto J, Takeda T, Toyama Y: Effect of walking exercise on bone metabolism in postmenopausal women with osteopenia/osteoporosis. Journal of Bone and Mineral Metabolism 22:500-508, 2004
5. Johansen KL: Physical functioning and exercise capacity in patients on dialysis. Advances in Renal Replacement Therapy 6:141-148, 1999
6. Ubara Y, Tagami T, Nakanishi S, Sawa N, Hoshino J, Suwabe T, Katori H, Takemoto F, Hara S, Takaichi K: Significance of minimodeling in dialysis patients with adynamic bone disease. Kidney International 68:833-839, 2005
7. Spindler A, Paz S, Berman A, Lucero E, Contino N, enalba A, Tirado S, Santana M, Zeballos A: Muscular strength and bone mineral density in haemodialysis patients. Nephrol. Dial. Transplant. 12:128-132, 1997
8. Chamay A, Tschantz P: Mechanical influences in bone remodeling. Journal of Biomechanics 5:173-180, 1972
9. Kouidi E, Albani M, Konstantinos N, Megalopoulos A, Gigis P, Guiba-Tziampiri O, Tourkantonis A, Deligiannis A: The effects of exercise training on muscle atrophy in haemodialysis patients. Nephrology Dialysis Transplantation 13:685-699, 199