Exercise as it relates to Disease/Intense Exercise - The effects on coronary collateral circulation in patients with coronary artery disease

This is a review of the journal article 'Coronary Collateral Growth Induced by Physical Exercise' by Sven Möbius-Winkler et al, Volume 133, Issue 15.

What is coronary artery disease?
Coronary artery disease (CAD) is the most common form of human heart disease, whereby the build up cholesterol and plaque harden the walls of the arteries to cause what is known as atherosclerosis. This in turn, causes a reduction in the amount of blood flow and oxygen to the heart, thus potentially resulting in the suffering of a heart attack.

What is collateral circulation?
Collateral circulation is viewed the re-directing of blood circulation around the clogged artery. In regards to CAD, the function of collateral circulation is the ability to bypass the blockages caused by the plaque build up and go onto supplementing the heart with enough oxygen to help ensure the cardiac tissue is able to survive.

What is High Intensity Training and Moderate Intensity Training

 * High intensity exercise is best utilized through HIIT, or high-intensity interval training, which is a training technique whereby the subject expels maximal energy and effort over a short period of time followed by a period of rest. This process is repeated over an allotted period of time, with maximal energy expenditure being the focus of all periods of 'work'.
 * Moderate intensity exercise is best utilized through steady state exercise, which can be further broken down into; 1 - An activity that is performed at a a steady constant pace for an extended period of time. 2 - The balance between energy required and energy available during exercise over an extended period of time.

Health Risks of Coronary Artery Disease
There are many risk factors of Coronary Artery Disease including;

•	High Blood Cholesterol

•	High Blood Pressure

•	Diabetes

•	Obesity

•	Nutritional Intake

•	Hormonal Stress Levels

•	Level Of Physical Activity

Where is the research from?
The study from 'Circulation' by Möbius-Winkler et al looked at the results of the Impact of Intensive Exercise Training on Coronary Collateral Circulation in Patients With Stable Coronary Artery Disease.

What Type Of Research Is This?
This was a randomized control trial research study, as the groups were separated into 3 categories, with the results culminating at the end in order to give an effective verdict.

What Did The Research Involve?
This study was undertaken with 60 patients suffering from coronary artery disease into 3 delegated groups. Group A would be formed of 20, would be the High-Intensity Exercise group, Group B would be formed of 20 and would be the Moderate-Intensity group, and finally Group C, would be the controlled group which itself would consist of the final 20. The patients change in coronary flow index (CFI) after 4 weeks would be adjudicated to determine which form of intensity would be best suited to optimize coronary collateral circulation for those with coronary artery disease.

Results
After 4 weeks, the coronary flow index for both groups A and B, showed significant increase, with group C remaining mostly unchanged. The CFI for group A increased by 39.4% (from 0.142±0.07 at beginning to 0.198±0.09 at 4 weeks) with group B increasing by 41.3% (from 0.143±0.06 to 0.202±0.09), and group C remaining nearly unchanged, a total of 0.7%, (from 0.149±0.09 to 0.150±0.08).

What this shows, although both forms of intensity showing significant positive effects on those with CAD, that high-intensity exercise did not lead to a greater CFI than moderate-intensity training therefore cannot be deemed as a more beneficial form of intensity training in regards to coronary collateral circulation.

Important Findings
It is important to analyse the limiting factors in order to determine why the results were as they were. One factor of the study was the duration of only 30 days. Another factor is the level of 'high-intensity', studies have shown that high-intensity at its maximal threshold can only be attained through supervision (patient being pushed constantly). Finally, within the high-intensity group, the subjects exercised 4 times daily for 30 minutes. It can be assumed that this amount of exercise would not be undertaken by an ordinary patient, especially within the short time frame allocated. Thus, the decision to believe that both intensities have the same benefits, could only be assumed, rather than being effectively concluded.

Conclusions of Research
The research concluded that the 4 weeks of documented high intensity vs moderate intensity performed for the 10 hours per week resulted in a significant improvement in collateral flow index in comparison to the control group which remained without any form of intense exercise. Therefore, it can be said that the regular stimulation of collateral avenues activated by exercise proved beneficial for the collateral coronary arteries blood flow and would be an asset to those suffering from coronary artery disease.

This has been further supported by Tony Venuto, who wrote that for maximal benefits, a combination of both High intensity training combined with an extended amount of steady state exercise, optimizes the bodies ability to increase its VO2 max, thus strengthening the coronary collateral arteries circulation of blood flow. To continue on from that, research has also shown that high levels of intense exercise can burn into the muscle, which therefore for a patient suffering from CAD, would hinder the recovery process, so further research needs to be done in finding a happy middle ground.

Practical Advice
The results of this study did not give enough time for a significant answer to the debate over what type of activity is best suited for those with CAD. It can be recommended that future study take place over an extended period of time to allow for further measuring of the different levels of intensity. It can also be suggested that the patients all undergo a pre-screening prior to the research task, as although all suffer from coronary artery disease, some may still be more active than others and respond better to the different levels of training intensity. To get a clear understanding of the benefits, patients of equal aerobic levels need to be selected.

Further Information
Further information in order to compare other research articles to this can be found at the following:
 * What is Coronary Artery Disease? http://www.nhlbi.nih.gov/health/health-topics/topics/cad
 * What is HIIT? http://www.popsugar.com.au/fitness/What-HIIT-41016932
 * What is steady-state exercise? https://www.reference.com/health/steady-state-exercise-751e009afbf6b53e