# Exercise as it relates to Disease/Moderate Versus High Intensity Aerobic Training in Coronary Heart Disease Patients

This is a review of the journal article 'Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients' by Øivind Rognmo, et al.

## Background
### Coronary Heart Disease

Coronary heart disease (CHD) is a condition in which the heart's arteries (blood vessels) become narrower. This is caused by a process known as atherosclerosis: which is the gradual buildup of substances such as fat, cholesterol and calcium. Narrowing the arteries causes the heart to work harder in order to pump oxygenated and nutrient rich blood around the body. The gradual buildup of such substances can often be unrecognisable, and can cause blood clots to appear at the narrowing of the artery, angina and myocardial infarction

### Risk Factors

* Smoking
* High cholesterol
* Lack of regular physical activity
* Excess weight and obesity
* High blood pressure
* Diabetes
* Family history of heart disease
* Depression and social isolation

### Statistics on Coronary Heart Disease

Together with stroke and vascular diseases, coronary heart disease kills more Australians than any other disease group. Approximately 3.6 million Australians are affected by the disease group, with this number continuing to rise in correlation with the nations high obese rate. In 2012, the group claimed the lives of 43,900 Australians (30% of all deaths) - deaths that were largely avoidable.

### Physical Activity and Cardiovascular Health

In 1953, Morris et al. published the findings from a study showing that bus conductors who were required to walk the length of the bus, as well as climb up and down the stairs of the double decker bus, showed half the mortality rate from CHD than the driver counterparts who were not required to move off of the drivers seat. Since this paper, countless studies have been performed that further supports the findings by Morris et al. In 2008, a report developed by Physical activity guidelines committee in Washington, concluded that active people have significantly lower rates of cardiovascular disease than inactive ones.
Regular moderate intensity exercise has been shown to prevent blood vessels from narrowing further (anti-atherosclerotic), prevents blood clotting (anti-thrombotic), helps deliver blood to the heart (anti-ischaemic), and helps to maintain a normal heart rhythm (anti-arrhythmic). These changes reduce the load on the heart at rest and during exercise, which helps to lessen some of the symptoms as well as decrease the risk of death from CHD.
Generally, the exercise recommended for CHD patients tends to be of a moderate intensity. Few studies have been conducted in order to establish the effects of moderate versus high intensity exercise. The difference between the two can be established with how the patient feels. Moderate intensity feels somewhat hard, when breathing quickens but doesn't struggle for breath. High intensity exercise is when breathing is deep and rapid, with a significant sweat developed after only a couple minutes of exercise.

## The Research
### Where was the Research Based From?

The authors of the article were Øivind Rognmo, Trine Moholdt, Hilde Bakken, Torstein Hole, Per Mølstad, Nils Erling Myhr, Jostein Grimsmo and Ulrik Wisløff, conducting the study on behalf of the American Heart Association. Lead author, Øivind Rognmo, is of the Norwegian University of Science and Technology, with his primary research focus being on cardiovascular adaptions of exercise training, from cellular physiology, via clinical adaptations, to benefits on population level. The pedigree of the researchers, along with the educational intentions of the research implies little bias toward the study especially since no sponsorship or organisational links are evident other then funding from the research council of Norway, and the Norwegian council of cardiovascular disease.

### Type of Research

The study conducted was a randomised control trial (RCT), meaning that it involved group to be controlled under differing conditions in order to compare and contrasts the results of each group. The research is consistent with similar studies in terms of population size, applicability of the subjects (all subjects were enrolled in rehabilitation units), and safety measures put in place (all subjects were given an ECG test prior to testing).

### What did the Research Involve?

The research consisted of 4846 patients (male, 70%; female, 30%) who were referred to an exercise-based cardiac rehabilitation program at 3 different rehabilitation units in Norway between 2004 and 2011. Mean age was 57.8 years. All CHD patients taking part in this survey were enrolled at the rehabilitation units. High intensity training modules were designed to hit 85-95% max heart rate, whilst the moderate intensity modules were closer to 65% max heart rate, with all sessions lasting 60 minutes. Typical training modalities included outdoor walking, biking sessions, treadmill exercise and cross country skiing (article).

### Conclusions and Practical Implications

The study found that the risk of cardiovascular event after both moderate and vigorous intensity exercise is low. The authors have seen the results be placed in various rehabilitation units across Norway, with the vigorous intensity exercise modality especially being praised considering that previous hypothesis' have generally only enforced moderate intensity exercise CHD patients. Despite this, the findings were greeted with caution, as the authors identified the low number of casualties as a possible bias toward the result of the study. They recommend that further high intensity exercise studies on CHD patients be collected in order to clear up the safety aspect of the research.
The conclusion of the study should be taken with a grain of salt. Although the authors of the study have already recommended that high intensity exercise modules be applied within a clinical setting across rehabilitation centres in Norway, it is rather naïve to believe the area need far more focus for anything conclusive to be applied in the rehabilitation of CHD patients. The common generalisation is that moderate intensity exercise has always been recommended for CHD patients and that vigorous intensity exercise avoided. Despite this, however, a similar study conducted by Sven Möbius-Winkler et al., findings were similar in that both moderate and high intensity exercise modules were beneficial to coronary artery disease patients. So although further research is required, the outlook looks promising to apply these training modules to clinical settings. The study also warned against the use of high intensity exercise for CHD patients that are obese or exhibit sedentary behaviour, as the likelihood of myocardial infarction is far greater.
The research is able to present CHD patients with important considerations for the controlling of the chronic disease, but nothing to do with prevention. It is highly recommended that readers take on the advice of professional medical practitioners, before heeding to any of the advice presented by this study. Especially for those that are looking at controlling CHD and do not exercise regularly.

### Further Information

Readers can benefit further by visiting the following scholarly articles and institutions that provide invaluable information for CHD control, prevention and implications:
* National Heart Lung and Blood Institute (NHLBI) https://www.nhlbi.nih.gov/
* Thompson, P. D., Franklin, B. A., Balady, G. J., Blair, S. N., Corrado, D., Estes, N. M., ... & Maron, B. J. (2007). Exercise and acute cardiovascular events placing the risks into perspective: a scientific statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism and the Council on Clinical Cardiology. Circulation, 115(17), 2358-2368.
* NHS (National health service of UK. Available at: http://www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Introduction.aspx
* NCBI available at http://www.ncbi.nlm.nih.gov/pubmed/20369114

## References

* 1 2 Rognmo, O., Moholdt, T., Bakken, H., Hole, T., Molstad, P., Myhr, N., Grimsmo, J. and Wisloff, U. (2012). Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients. Circulation, 126(12), pp.1436-1440.
* 1 2 Heart Research Australia. (2016). Coronary heart disease. [online] Available at: http://www.heartresearch.com.au/coronary-heart-disease.html [Accessed 27 Sep. 2016].
* 1 2 Nhlbi.nih.gov. (2016). What Is Coronary Heart Disease? - NHLBI, NIH. [online] Available at: http://www.nhlbi.nih.gov/health/health-topics/topics/cad [Accessed 27 Sep. 2016].
* ↑ myVMC. (2005). Coronary Heart Disease (CHD) | myVMC. [online] Available at: http://www.myvmc.com/diseases/coronary-heart-disease-chd/ [Accessed 27 Sep. 2016].
* ↑ Australian Bureau of Statistics. Causes of death 2012 (3303.0). March 2014
* ↑ Morris JN, Heady JA, Raffle PA, Roberts CG, Parks JW. Coronary heart-disease and physical activity of work. Lancet. 1953; 265: 1053–1057;contd
* ↑ Physical Activity Guidelines Committee. Physical Activity Guidelines Advisory Committee Report. Washington, DC: Dept of Health and Human Services; 2008.
* ↑ Taylor RS, Brown A, Ebrahim S, Jolliffe J, Noorani H, Rees K, et al. Exercise-based rehabilitation for patients with coronary heart disease: systematic review and meta-analysis of randomized controlled trials. Am J Med. 2004;116:682-92
* ↑ Mayoclinic.org. (2016). Exercise intensity: How to measure it - Mayo Clinic. [online] Available at: http://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/exercise-intensity/art-20046887 [Accessed 27 Sep. 2016].
* ↑ Möbius-Winkler, S., Uhlemann, M., Adams, V., Sandri, M., Erbs, S., Lenk, K., Mangner, N., Mueller, U., Adam, J., Grunze, M., Brunner, S., Hilberg, T., Mende, M., Linke, A. and Schuler, G. (2016). Coronary Collateral Growth Induced by Physical ExerciseCLINICAL PERSPECTIVE. Circulation, 133(15), pp.1438-1448.