The Nutritional Benefits of Exercise
Incorporating a consistent exercise routine can significantly modify risk for CKD patients.
Resistance exercise added to oral supplements may boost net muscle protein balance.
Exercise is an important though often overlooked component to improving nutrition-related outcomes, especially for those with CKD. According to the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (K/DOQI) clinical practice guidelines for managing dyslipidemia in CKD, exercise has a number of beneficial effects and should be encouraged (Am J Kidney Dis. 2003;41[4 Suppl 3]:S1-S91).
Reinforcing that message, K/DOQI clinical practice guidelines for CVD in dialysis patients advise that “all dialysis patients should be counseled and regularly encouraged by ne-phrology and dialysis staff to increase their level of physical activity” (Am J Kidney Dis. 2005;45[4 Suppl 3]: S1-S153).
CVD is the leading cause of death in stage 5 CKD patients, and exercise may decrease certain risk factors. A recent study by Mozaffarian et al (Circulation. 2008; 118:800-807) looked at the effect of routine walking and leisure activity on incidence of atrial fibrillation (AF).
A total of 5,446 subjects aged 65 years and older were followed for 12 years as part of the Cardiovascular Health Study funded by the National Heart, Lung, and Blood Institute. Results showed a U-shaped relationship between the incidence of AF and no exercise, light-to-moderate leisure-time activity (about 600 kcal/week), walking (the equivalent of about 12 blocks per week at 2 mph), and high-intensity exercise.
The authors conclude that “light-to-moderate physical activities, particularly leisure-time activity and walking, are associated with significantly lower AF incidence in older adults.”
Protein malnutrition occurs frequently in people on dialysis, and the use of resistance exercise in combination with enteral or parenteral nutritional supplements during hemodialysis has been examined as a possible remedy. A study by Majchrzak et al (Nephrol Dial Transplant. 2008;23:1362-1369) of eight maintenance hemodialysis (MHD) patients found that resistance exercise in addition to oral nutritional supplements resulted in a significant increase in net muscle protein balance. Although results were based on just one session, the authors suggest “they provide an intriguing strategy to prevent and/or treat uremic wasting syndrome.”
Similarly, Pupim et al (Eur J Clin Nutr. 2007;61:686-689) looked at the potential benefit of exercise during administration of intradialytic parenteral nutrition (IDPN) in a study of five MHD patients, with results indicating “exercise performance during hemodialysis significantly improves the fractional synthetic rate…of albumin beyond what is observed with IDPN alone.”
Exercise has also been shown to improve quality of life in hemodialysis patients and may aid in decreasing restless legs syndrome (RLS). A study by Sakkas et al (ASAIO J. 2008;54:185-190) examined the effects of intradialytic aerobic exercise in 14 MHD patients. The authors report that 45 minutes of supervised exercise thrice weekly for 16 weeks yielded a 42% decreased International RLS score and “significantly improved indices of functional ability, exercise capacity, quality of life, and sleep quality.”
A review article by Kirsten L. Johansen, MD, of the nephrology department at the San Francisco VA Medical Center (Hemodial Int. 2008;12:290-300), highlighted the results of intervention studies of exercise in dialysis patients.
Dr. Johansen notes “there is ample evidence that exercise can improve cardiovascular risk factors in the dialysis population.” She acknowledges, however, that “there is no consensus regarding the most beneficial regimen.” The article provides a summary of recent recommendations of the American College of Sports Medicine and the American Heart Association that pertain to exercise among older adults and those with chronic disease.
These recommendations “emphasize that aerobic activity should be moderate relative to an individual's level of fitness rather than on an absolute scale according to recommendations for younger, healthier populations and that activity can be accumulated through individual bouts of exercise as short as 10 minutes."
Although evidence supporting the benefits of exercise in CKD is ac-cumulating, initiating this lifestyle change can be a challenge. Kontos et al (Int Urol Nephrol. 2007;39:1303-1311) examined factors impacting exercise participation in older adult MHD patients. Information from focus-group discussions with 18 patients and caregivers revealed major obstacles, including lack of encouragement to exercise, transportation issues, and need for appropriate adaptive equipment for patients who cannot use exercise bicycles.
The authors suggest that “broadening the understanding of the factors influencing exercise participation will help to facilitate the development of interventions that have a greater likelihood of success.”
Recommendations for incorporating exercise into the routine care of dialysis patients by Kutner (Int Urol Nephrol. 2007;39:1281-1285) are:
- Making available in-center programs (i.e., exercise cycling);
- Connecting with community programs (walking, water exercise, swimming);
- Physical therapy referrals as indicated;
- Staff commitment to the importance of physical activity;
- And including questions about exercise as part of regular patient assessments.