Exercise as it relates to Disease/Exercise for chronic heart failure patients, Continuous vs Intermittent

This is a criticial analysis of the research artcitle "A Comparison of 16 Weeks of Continuous vs Intermittent Exercise Training in Chronic Heart Failure Patients" by Niel A. Smart PHD and Michael Steel PHD, published on the 27th of November 2011.

This critique was written as an assessment for the unit, Health, Disease and Exercise at the University of Canberra, September 2020.

What is the background to this research?
Congestive Heart Failure or CHF is the inability of the heart to effectively transport enough blood to fulfil the needs of the body. CHF is commonly associated with Coronary Heart Disease, high blood pressure, heart attacks, abnormal heart rhythms, heart valve issues and cardiomyopathy. Major risk factors that can cause these afflictions are physical inactivity, high cholesterol, unhealthy diet, obesity, diabetes, and smoking. The purpose of this study conducted by Smart and Steel was to look at a comparison between continuous vs intermittent exercise in treating patients with stable heart failure. The reason behind this study was to test whether intermittent (INT) exercise training would cause similar adaptions to left ventricle function and overall heart functionality of patients with chronic heart failure as continuous (CON) exercise training of equal exercise volume. This was considered as research into improvement of left ventricle functionality was limited in terms of exercise while endothelial function improvement after exercise in chronic heart failure patients has been demonstrated in several reports.

Where is the research from?
The research was conducted by the School of Science and Technology at the University of New England located in the state of NSW in Australia. The research took results from 23 patients with congestive heart failure. Neil Smart received a scholarship from the National Heart Foundation of Australia which helped finance the research with aid from the Mutual Benefit Fund.

What kind of research was this?
The type of research conducted was a randomized control study as it looked at patients who were already with CHF but would be split into two differing exercise programs, control been CON and experimental been INT. In randomized control studies, the only expected difference / differences is the outcome variable been studied. 23 patients with CHF with the INT exercise program having a mean age of 59 while the patients partaking in the CON exercise program having a mean age of 61. These patients were already involved in exercise programs as part of their treatment for CHF but would continue with the exercise programs selected for them as part of the randomized control study. CHF patients were selected for the study with four identifying factors linking them to CHF. These been a left ventricular ejection fraction of under 35%, (Amount of blood that is successfully pumped out of the left ventricle with each individual heart pump), two minor criteria and one major criteria from the Framingham diagnostic criteria in terms of heart failure. An ethical committee in relation to the Framingham study approved the patients with these criteria’s taking part in the story. Patient selection also occurred through the testing of their V02 max as this is good indicator of whether they are able to start / remain on an exercise program or not. Patients were excluded from been involved in the study if they displayed symptoms of unstable angina, primary valvular disease or had an inability to exercise. There was also no large diversion in terms of the patients baseline results in both groups.

What did the research involve?
The research involved the 23 patients to partake in either an INT exercise program or CON exercise program, with the patients been split 10 (INT) and 13 (CON) in their respective groups. The patients were prescribed to take part in these programs for a period of 16 weeks. The training consisted of cycling on an ergometer at a level of 60%-70% of their peak VO2 max that had been found previously from cardiopulmonary exercise testing on a cycle ergometer through a breath by breath analysis of expired gas. The initial training workload was also calculated using the peak heart rate and peak workload found from the testing done before the training programs commenced. Patients in the CON exercise program would do three 30min continuous exercise sessions per week while patients in the INT exercise program would do 60min of intermittent exercise sessions per week with both groups completing the same amount of total work volume per week. Exercise intensity was increased by 2-5 watts per week if the patients were keeping up and maintaining exercise intensity. RPE (rate of perceived exertion) was also used to increase or decrease exercise intensity for the patients, this was relevant for patients who experienced frequent ectopy. Shortness of breath in patients was also a method used to measure and change exercise intensity. Baseline clinical and pharmacologic characteristics were recorded before the 16 weeks and after taking into account their age, body mass index, peak VO2 and left ventricle ejection fraction as well as Framingham’s heart criteria and current medication. Baseline clinical and pharmacologic characteristics were recorded before the 16 weeks and after taking into account their age, body mass index, peak VO2 and left ventricle ejection fraction as well as Framingham’s heart criteria and current medication. The patient’s wellbeing / quality of life were taken into account with the use of the Hare/Davis Cardiac Depression scale and the Minnesota Living with Heart Failure quality of life score. Functional capacity of cardiac function was recorded before and after the 16 weeks and would be used to see as the main indicator to compare between CON and INT.

What were the basic results?
The basic results were that functional capacity of the patients improved in both groups but a larger improvement was seen from the INT group. VO2 max in the INT patients saw an increase of 21%. Significantly higher than that of the patients in the CON group who’s VO2 max increased by 13%. Ventilatory efficiency improved in the INT group but the patients in the CON group saw little to know change from the results 16 weeks before. This was measured by using a minute ventilation carbon dioxide production slope. Left Ventricular ejection function remained relatively unchanged in both groups pre and post 16 weeks. MLWHF score was unchanged in the INT group and changed slightly in the CON group but with no significant changes between groups. The Hare/Davis cardiac depression scale, the scores of both groups increased within the 16 week period.

What conclusions can we take from this research?
The conclusions that can be taken from this research is that INT exercise programs can have a greater affect on physical functionality of patients with CHF than CON exercise programs. This is because the INT group had a far greater change in their VO2 max after the 16 weeks than the CON group. The authors suggest this is a physical adaption that occurs due to the more time that the heart is under stress during the individual training sessions due to the INT training sessions lasting for 60min. Double the time than the CON sessions even though the workload remains the same over both. The authors state this is consistent with previous 16 week studies that have tested functionality. Quality of life improves over the 16 weeks as well and as remained consistent with research relating to it.

Practical advice
What can be taken from the research conducted is that Intermittent exercise should be considered more as an effective treatment over continuous exercise in treating patients who have Congestive Heart Failure who are under medication protocols and have their exercise treatment supervised by professionals. More research must be put into exercise treatment for CHF as the authors admit that the research conducted may only be relevant to CHF patients who are relatively young as the mean age for both groups were 59 (INT) and 61 (CON) and may not be relevant to older CHF patients. The authors also state that the small sample size and not having an equal amount of women to men (only 2 patients were women) would question the validity of the research.

Further information/resources

 * 1) Heart Foundation
 * 2) Classes of Heart Failure
 * 3) Congestive Heart Failure