Exercise as it relates to Disease/The effect of exercise training on renal function in chronic kidney disease patients

This page is a critique of the research article "Exercise therapy correlates with improving renal function through modifying lipid metabolism in patients with cardiovascular disease and chronic kidney disease" conducted by Toyama K et al. (2010)

What is the background to this research?
Chronic kidney disease (CKD) refers to reduced function of the kidneys over a lasting period of time, and may require a kidney transplant and even lead to death. CKD affects 13.4 percent of the population worldwide as of 2016, therefore clearly requires clinical attention and intervention.

This study largely focuses on CKD indicators such as differences in glomerular filtration rate (GFR) and lipoprotein metabolism. CKD is typically characterised by a relatively low GFR, low plasma high density lipoprotein cholesterol (HDL-C) concentrations, high plasma low density lipoprotein cholesterol (LDL-C) concentrations, and high plasma triglycerides. In terms of treatment, literature often emphasises dialysis or transplantation for severe cases, dietary interventions, and certain medications. Although these methods of treatment are relevant and effective, exercise prescription as treatment is often overlooked or disregarded.

Where is the research from?
This study was conducted in Kumamoto, Japan. Koyama, Sugiyama, Sumida and Ogawa are from the Department of Cardiovascular Medicine, Faculty of Life Science, Graduate School of Medical Sciences, Kumamoto University. Oka is from the Division of Cardiology, Health Insurance Hitoyoshi General Hospital.

These authors appear to be extremely qualified and reliable, having published over 1000 peer-reviewed journal articles/documents between them, many of which are in the area of cardiovascular disease, diabetes etc. (i.e. similar conditions to CKD). There would be the potential for bias towards exercise prescription as a treatment method if the authors had a strong background in exercise science; however, they are mostly involved in more clinical/medicinal operations. If anything, this makes the study seem more reliable, as these experienced professionals went outside of typical treatments to find success with exercise treatment.

What kind of research was this?
This research was in the form of a prospective open-labelled clinical trial. This involves two groups of patients diagnosed with CKD, where all participants and researchers are aware of the circumstances of the study. Study conditions are prescribed for a 12-week period. Measures are taken prior to the intervention and at the end of the 12-week period, and differences between the two groups pre- and post-intervention are observed. Different types of studies may have different degrees of effectiveness. Prospective cohort studies are considered to be the gold standard in epidemiological study design, with emphasis on being unbiased. Therefore this study should theoretically produce reliable results.

What did the research involve?
19 participants with CKD were divided into two groups: an exercise training (ET) group (n=10) and a non-exercise training (non-ET) group (n=9). Both groups were prescribed an intervention in the form of diet therapy, mental support, counselling for medication, and CVD/CKD education. The ET group (unlike the non-ET group) were additionally prescribed an exercise program that involved a weekly 30 minute bicycle ergometer session in the hospital, as well as daily 30 minute home exercise (walking at 12-13 RPE on Borg Index). All participants underwent pre- and post-intervention blood sampling and cardiopulmonary exercise tests to determine anaerobic metabolic threshold (AT-VO2). Baseline measures of a large range of health markers were also taken for both groups.

This methodology seems effective, although 30 minutes of daily walking seems too short in duration for such a light exercise. So perhaps extending those walking bouts to one hour would produce stronger results. The study is also quite low in the number of participants, which is understandable as it may be difficult to recruit a large number of willing CKD patients. Since these patients are diagnosed with a chronic disease that involves numerous health restrictions, they would be at high risk when participating in the cardiopulmonary exercise tests and the exercise program itself. Therefore caution should be taken throughout the study.

What were the basic results?
Figure 1: Changes in health markers over the 12-week period

Results shown in figure 1 are interpretations of the results given in the study, where extents of increase/decrease are relative to each other. The main findings in the study were displayed in the form of bar graphs comparing the ET group to the non-ET group. This form of display may have visually emphasised the desired results, although all results were still statistically significant with p-values <0.05.

For example, in the ET group:
 * HDL-C concentration increased from ~40mg/dl to ~55mg/dl
 * LDL-C concentration decreased from ~115mg/dl to ~75mg/dl.

All results shown in the study favour the implementation of an exercise training program for improving health in CKD patients.

What conclusions can we take from this research?
Exercise prescription is an effective way of improving renal function in CKD patients, particularly through lipid metabolism. If something as little as a 12-week exercise program that is relatively light in intensity displayed such significant results, then increasing the load and extending the program could do much more.

More recent research has aligned with these findings, and specified that aerobic exercise at an intensity of >60% maximum capacity is recommended. It further suggests exploring resistance training for potentially reducing inflammatory responses.

Practical advice
For those with CKD or reduced renal function/lipid metabolism; daily, light-moderate exercise for >30 minutes can significantly improve these health aspects. Increased benefits may come with longer bouts of exercise. Speak with a medical professional beforehand and proceed with caution as the may be a high risk of injury/events.


 * CKD Information: http://www.health.gov.au/internet/main/publishing.nsf/Content/chronic-kidney
 * CKD Management handbook: https://kidney.org.au/health-professionals/prevent/chronic-kidney-disease-management-handbook
 * CKD Support groups: https://kidney.org.au/connect/support-groups/community-support