Exercise as it relates to Disease/The immediate and long-term effects of exercise on blood pressure in patients with chronic kidney disease

Background

This particular study was designed to determine if there is a relationship between immediate and long-term blood pressure (BP) responses to aerobic exercise in pre-dialysis patients. High blood pressure is a risk factor for the development and progression of chronic kidney disease (CKD) and is also linked with the development of cardiovascular disease, which in turn is the leading cause of death in CKD patients. It was found that just one exercise session can produce a significant reduction in systolic blood pressure (SBP) in individuals with hypertension and this effect can last for up to 22 hours. This phenomenon is called post-exercise hypotension (PEH) and it can be used to identify which patients respond favourably to the blood pressure (BP) reducing effects of exercise. Chronic aerobic training also leads to a reduction in (SBP) and diastolic blood pressure (DBP) in approximately 75% of the hypertensive population. There is also evidence that SBP and DBP can be reduced in pre-dialysis CKD patients following a period of exercise training.

Where is the research from?

This research was conducted at the Wellness Centre at Springfield College in the United States of America and other institutional affiliations were the Renal and Transplant Associates of New England, University of the Rockies, University of Hartford and the University of Connecticut.

What kind of research was this?

Forty-six CKD patients performed a randomised controlled trial (RCT) in order to get the results for this particular research. In a RCT people are allocated at random to receive one of many clinical interventions. Someone who takes part in a (RCT) is a patient or subject and these individuals are placed in a control group where they will receive intervention and another group where they will have no intervention at all.

What did the research involve?

The forty-six patients in this research all suffered from CKD, were ranged between ages 35–70 years and all had either diabetes mellitus or hypertension as their main cause of their kidney disease. Patients who smoked cigarettes, were involved in an exercise program, had atrial fibrillation or presented any absolute contradiction to exercise as defined by the American College of Sports Medicine were excluded from the research. All testing was performed at the Wellness Centre at Springfield College.

Subjects attended four preliminary testing sessions before being separated into the treatment (T) and control (C) groups. During the first session, accurate SBP and DBP readings were taken from all the patients and for the 24 hours after the readings they wore a 24-hour ambulatory blood pressure monitor (ABPM) to analyse changes in BP. Anthropometric and resting BP measures of the subjects were taken in the second session as well as conduction of a cardiopulmonary exercise test (CPX). Peak oxygen uptake (VO2peak) is a measurement of an individual's aerobic capacity and this was measured in the subjects by using a breath-by-breath computerised metabolic system. VO2peak was used to quantify the exercise intensity used in the study. Once the subject reached their peak functional capacity the test was terminated and they were made to use the ABPM for the following 24 hours. In the third and fourth sessions, subjects went into the laboratory after an 8-hours food fast, water was encouraged to be consumed freely. During one these sessions BP readings were taken of the patients after they walked on a treadmill for a total of 40 minutes and in the other session BP readings were taken every 10 minutes for a total of 60 minutes whilst the subjects sat quietly. After these sessions patients were made to wear the ABPM for the following 24 hours.

Exercise: The subjects who were randomised into the T group were asked to attend three supervised sessions per week for 16 weeks. Subjects initially trained at 50-60% VO2peak for 15–30 minutes and then gradually increased to a total of 55 minutes. Subjects in the C group were asked to keep living their life as per normal and not to initiate an exercise program.

What were the basic results?

PEH was not affected by 16 weeks of aerobic endurance training and there was no relationship found between the magnitude of the initial PEH in the laboratory and the resting BP responses following the training program. The results of this study show that an 8.3% increase in peak oxygen uptake was evident after the 16-week program. The increase in aerobic capacity did not result in significant reductions in BP. Results could be different if the patients in this study were not using antihypertensive medication but it would be unethical to make patients perform the study without medication in order to get "pure" results.

What conclusions can we take?

The results from this study confirm that CKD patients experience PEH following an acute bout of exercise but PEH is not affected by 16 weeks of moderate intensity aerobic exercise. The occurrence of PEH does not appear to predict how a patient with CKD could respond to a period of chronic aerobic training. With these results in mind it seems as though a period of supervised training that is enough to improve the aerobic capacity of CKD patients does not appear to have an effect on their BP.

Practical Advice

Considering the results of this research, even if a change in BP is not apparent after chronic exercise, PEH does appear to occur after a single session of exercise. With this in mind a patient with CKD will have BP improvements from every session of exercise they perform which means regular exercise is recommended.

Further Information/resources

Other studies on CKD patients show the magnitude of PEH was related to BP lowering effects following an 8-week exercise training program and that there was a relationship between PEH and resting BP following 4 weeks of training.