Exercise as it relates to Disease/The effects of high vs moderate-intensity exercise on coronary artery disease

This is a critique of the research article, Rognmo et al (2003). ‘High intensity aerobic interval exercise is superior to moderate intensity exercise for increasing aerobic capacity in patients with coronary artery disease’. European Journal of Cardiovascular Prevention and Rehabilitation. 2004, Volume 11, page: 216 – 222.

This critique was written as an assignment in the unit; Health, Disease and Exercise at University of Canberra, August – September 2019

Background to this Research
The purpose of the study was to find the effects of high – intensity aerobic interval training and moderate intensity aerobic interval training and which one was most effective on decreasing mortality in Coronary Artery Disease (CAD) patients.

Coronary Artery Disease is when the arteries that supply bloody to the heart muscles become harder and narrow, this is from a build up of plaque on the inner walls of the arteries.

The issue they are highlighting is that most patients with CAD only work at low to moderate intensity. Within the study they discuss the correlation between a high intensity workout and how it reduces the risk of cardiovascular disease (CVD) and reduces the progression of CAD.

This article highlights that if you have CAD how the level of exercise intensity helps to reduce the affect it has on your life. It is important that patients with CAD are maintaining physical activity in order to help maintain their disease and prevent mortality.

Research
The study involved 21 participants who must have at least CAD in one major epicardial vessel and lived within 40 km of the hospital. Epicardial vessels are the vessels that remain on the surface of the heart. In addition, the medications that the participants were on were not different. A randomisation code was used to divide the participants into two groups to determine if they were in the high intensity (11 participants) or moderate intensity group (10 participants). This means the study was a randomised controlled trial, which means they are trying to reduce the amount of bias when testing effectiveness of a new treatment. As the participants had to live within 40 km of a hospital, there is a potential that the participants may have been manipulated to meet this specific requirement.

The study was conducted in Norway at Trondheim University Hospital in the Department of Circulation and Medical Imaging. All participants had undergone a medical investigation for CAD at the hospital the year prior to the study being conducted. This study was supported by grants from the Department of Cardiology at St Olavs Hospital, which could cause a bias in the results and findings as the research paper is being funded by a cardiology department. There could also be a conflict of interest because the study was conducted at St Olavs Hospital, which may have also influenced the interpretation of the results to highlight what they wanted to see. Additionally, as this study was conducted in Norway it may not be relevant to the Australian population as they have a different diet and exercise guidelines compared to Australia.

Methods of Study
A 12 point Electrocardiogram (ECG) was set up for every test. Patients were measured at rest before the exercise and at the end of each work level. Patients were stopped if an indication by the patients for terminations was presented. The researchers familiarised the patients with the treadmill by getting them to walk on the treadmill without holding the handles. Once the patients were comfortable with this and could walk without holding the rails, the speed started to increase and incline was adjusted, this was followed for 10 minutes as a warmup. After the warmup was completed they placed a face-mask on the patients to measure metabolic measurements. They used a protocol called ramp which is when the speed is a constant with a 2% increase in the incline every 2 minutes until VO2 peak max was reached.

The data was collected over 10 weeks during 2004. The patients were informed they were not allowed to perform exercise out of these protocols. This was a necessary part of the control to make sure no one was exercising out of the protocols and ensure accurate interpretation of the results.

Both groups were assigned to an Exercise Physiologist who ran the sessions for each group. Each group met 3 times a week for 10 weeks, each session went for 33 minutes. There was no changes in the groups exercise besides intensity levels. It is good they kept the exercises the same however, this could have been boring for the participants as it may have become repetitive and this may have influenced a desire to exercise outside of the training program.

Results
The main findings indicate that both groups significantly increased their VO2 peak before and after the training. The difference in each groups results were calculated using the U-Test. A two tailed P< 0.05 was accepted as statistically significant for all tests. The difference in P - value for moderate intensity was P<0.02 and for high intensity was P<0.05. Which resulted in a 17.9% improvement in the high intensity group compared to a 7.9% improvement in the moderate intensity group.

The researchers stated that the improvement was significantly higher in the higher intensity group. As all patients wore heart rate monitors they were able to adjust the workload based on their heart rate which caused them to find higher adaptations to the training and resulting in higher VO2 peak.

The results are consistent with the method as the high intensity group had better adaptations to the training and their VO2 peak increased higher, which makes sense as they are working at a high – intensity then the moderate – intensity group.

As there were a low number of participants this may not be a very reliable source of the interpreting the results. It would be desirable repeat the study to ensure that the conclusions drawn are more accurate. Further, as outlined in a study conducted by Lee MI whilst there is a correlation between exercise intensity, there needs to be considerations in the patients fitness levels before commencing moderate intensity exercise.

Conclusion
To conclude, the research demonstrated that high to moderate intensity exercise will increase VO2 peak max within patients with Coronary Artery Disease. This study has shown that people with Coronary Artery Disease should exercise aerobically at least 3 times per week at a moderate to high intensity which my in turn reduce their risk of mortality. Overall, the study has a good experimental design, however they had a small population of participants, so it would be desirable to repeat the research to ensure that the results achieved are repeatable. Additionally, as the cardiology department funded this research thee is a perceived conflict of interest which may question the validity of the study. The results from this study would be very helpful for Exercise Physiologists to create an exercise program for CAD patients. There is limited information and other studies to support this research on the effects of exercise intensity in CAD patients. However in one particular study it was found that understanding a patients existing fitness level may be a consideration rather than the level of exercise intensity they perform.

= Practical Advice =

For patients with CAD or people who are at risk to this disease it is best that they work with an Exercise Physiologist. This is important as they are able to see if any issues appear and so they are able to terminate the exercises. It is also important as an Exercise Physiologist is able to write up an exercise program for patients. Another option is for patients to go to their General Practitioner and ask to join a Cardiac Rehabilitation Program which if you have had surgery for CAD you should already be doing. The exercises you want to complete are aerobic and Strength training, as these are the best exercises to increase your heart rate via aerobic and strength training. You should aim to exercise at least 3 times a week for adaptations to occur. You are wanting to target large muscle groups, the exercises you can do are walking, running, cycling and swimming just to name a few.