# Exercise as it relates to Disease/Does physical activity help to reduce the risk of coronary heart disease?

This is a review of the journal article 'CORONARY HEART DISEASE AND PHYSICAL ACTIVITY OF WORK' by J. N. MORRIS and MARGARET D. CRAWFORD.

## Background
### What is Coronary Heart Disease?

Coronary Heart Disease (CHD) is the narrowing of the coronary arteries due to the gradual build-up of a waxy substance, known as plaque (fat, cholesterol, and calcium). This narrowing affects the hearts ability to receive oxygenated, and nutrient rich blood. The building-up of plaque occurs gradually overtime and this condition is known as atherosclerosis. Furthermore, a patent suffering from atherosclerosis, can experience the complete and/or partial blockage of blood flow. As a result, if the continuous blood flow to your heart is reduced or blocked, this can lead to the onset of a fatal heart attack or angina occurring (chest pain of discomfort).

### Risk Factors of Coronary Heart Disease

| Controlable | Uncontrolable |
| High LDL (Low-density lipoproteins) | Age |
| Low HDL (High-density lipoproteins) | Gender |
| High triglyceride levels | Family history |
| Obesity | |
| Blood pressure | |
| Diabetes | |
| Smoking status | |
| Diet | |
| Stress | |
The greater the number of coronary heart disease risk factors you have, the greater the risk it is for you to develop CHD.

### History and Facts About Coronary Heart Disease

Heart disease is the single most leading cause of death in Australia. In 2013, over 19,766 Australians lost their lives due to CHD. When averaged out, this equates to one Australian dying as a result of CHD every 27 minutes. From 2004 to 2013, CHD related deaths has fallen by 20% from 24,576 to 19,766.

### The Definition of Physical Activity and its Importance to Your Health

The World Health Organisation defines physical exercise as 'any bodily movement produced by skeletal muscles that requires energy expenditure'. Insufficient physical activity is a key risk factor for noncommunicable diseases, such as cardiovascular diseases (e.g. CHD), cancer and diabetes.
Physical activity or the reduction of a sedentary lifestyle can aid to improve physical fitness and overall health, as well as, reduce many coronary heart disease risk factors, including;
* Lower bad (LDL and total) cholesterol levels
* Increase good (HDL) cholesterol levels
* Controlling high blood pressure
* Aid losing excess body fat
* Increase insulin sensitivity
With regular exercise, individuals will experience a reduced risk of;
* Blood vessels narrowing (anti-atherosclerotic),
* Blood clotting (anti-thrombotic)
And an increase in;
* Delivery of blood to the heart (anti-ischaemic),
* Ensure a normal heart rhythm (anti-arrhythmic)

## About the research
### Where was this Research From?

The lead authors were J. N. Morris and Margaret D. Crawford from the Social Medicine Research United of the Medical Research Council, based in the London Hospital. This study was conducted in 1951. Where J. N. Morris and Margaret D invited over 206 hospitals to participate, of those, between 85% to 90% agreed to send them 25 consecutive, unselected necropsies on men aged between 45–70 years, ignoring what the cause of death was. In total, over 5,000 reports were surveyed and examined. Of the 5,000 reports, two experts examined the work/job each individual was in and classed the reports into physical activity categories. These two individuals used a three-point scale, "light" (e.g. bus-driver, clerk), "active" (e.g. postman, carpenter) and "heavy" (boilermaker, dock labourer) to determine each individuals physical activity levels.

### What were the Findings From this Research?

J. N. Morris and Margaret D. Crawford concluded that individuals had a lower prevalence of ischaemic myocardial fibrosis amongst men who had been in physically active and heavy jobs, as compared to those men who were classes in the sedentary and light jobs. Furthermore, they concluded that men in physically active jobs have a much smaller risk of developing coronary heart disease, and whilst the small disease they did have is often less severe. Men in physically active jobs who ended up developing CHD, tend to develop the condition a lot later in life, compared to those in physically inactive jobs.

## Physical Activity Guidelines to Reduce the Risk of Coronary Heart Disease

Physical activity is one of the primary preventative measures individuals can participate in to ensure their health and prevent on onset of coronary heart disease. Physical activity has been shown to reduce the risk factors associated with developing coronary heart disease.
Regular moderate-intensity exercise as well as resistance training has been shown to be beneficial in the prevention of developing coronary heart disease (CHD). Before any strenuous physical activity is undertaken.

### Types of Physical Activity to reduce the Risk of Developing Coronary Heart Disease

Moderate Physical Exercise
* Men who participated in 30 minutes for walking each day, saw a 18% reduction in coronary heart disease, compared to those who did not walk, and lead a majority sedentary lifestyle
High-Intensity (vigorous) Physical Exercise
* Men who participated in running an hour or men each week, saw a 42% reduction in coronary heart disease risk, compared to those men who did not run.
Resistance Exercise
* Men who participated in lifting weights for 30 minutes each week, saw a 23% reduction in coronary heart disease risk, compared with those men who did not lift weights.

## What Conclusions Should be Taken away from this Research?

Based on J. N. Morris and Margaret D. Crawford research, it can be concluded that leading a physically active lifestyle is essential to reduce the chance of developing coronary heart disease. This is done by lowering the risk factors associated with developing coronary heart disease, which will in-turn reduce the risk of developing coronary heart disease.

### Recommendations

The Australian Department of Health, recommends individuals between 18-64 to perform or participate in up to 150 to 300 minutes of moderate physical activity each week. Or, for individuals to perform or participate in high-intensity (vigorous) physical activity up to 75 to 150 minutes each week. While also performing muscle strengthening activities at least two days a week
Individuals following this guideline will experience a reduction in coronary heart disease risk factors, which will in-turn reduce the risk of developing coronary heart disease (CHD)

## Further reading

For further information of the benefits of physical activity is the prevention of Coronary Heart Disease; follow the links below:
* Exercise and Physical Activity in the Prevention and Treatment of Atherosclerotic Cardiovascular Disease: http://circ.ahajournals.org/content/107/24/3109
* Physical Activity in Prevention of Coronary Heart Disease: http://www.acc.org/latest-in-cardiology/ten-points-to-remember/2016/06/24/12/07/physical-activity-in-the-prevention-of-coronary-heart-disease?w_nav=LC

## References

* 1 2 3 4 5 Morris,J. N. and Crawford, M. D. 1958, Coronary Heart Disease and Physical Activity of Work, British Medical Journal, 2(5111) 1485–1496.
* 1 2 What Is Coronary Heart Disease? - NHLBI, NIH [Internet]. Nhlbi.nih.gov. 2016 [cited 26 September 2016]. Available from: http://www.nhlbi.nih.gov/health/health-topics/topics/cad
* 1 2 What Is Atherosclerosis? - NHLBI, NIH [Internet]. Nhlbi.nih.gov. 2016 [cited 26 September 2016]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/atherosclerosis
* ↑ What Are Coronary Heart Disease Risk Factors? - NHLBI, NIH [Internet]. Nhlbi.nih.gov. 2016 [cited 26 September 2016]. Available from: http://www.nhlbi.nih.gov/health/health-topics/topics/hd
* 1 2 3 Wilson PW et al. Prediction of coronary heart disease using risk factor categories. - PubMed - NCBI [Internet]. Ncbi.nlm.nih.gov. 2016 [cited 26 September 2016]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/9603539
* ↑ http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/3303.0~2013~Main%20Features~Leading%20Causes%20of%20Death~10001
* ↑ Physical activity [Internet]. World Health Organization. 2016 [cited 27 September 2016]. Available from: http://www.who.int/mediacentre/factsheets/fs385/en/
* ↑ Myers J. Exercise and Cardiovascular Health. Circulation. 2003;107(1). Available from: http://circ.ahajournals.org/content/107/1/e2
* 1 2 Taylor R, 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. The American Journal of Medicine. 2004;116(10):682-692. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15121495
* ↑ Physical activity - NHLBI, NIH [Internet]. Nhlbi.nih.gov. 2016 [cited 27 September 2016]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/heart-healthy-lifestyle-changes/physical-activity
* ↑ Warburton D. Health benefits of physical activity: the evidence. Canadian Medical Association Journal [Internet]. 2006 [cited 27 September 2016];174(6):801-809. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1402378/
* 1 2 3 4 Tanasescu M e. Exercise type and intensity in relation to coronary heart disease in men. - PubMed - NCBI [Internet]. Ncbi.nlm.nih.gov. 2016 [cited 27 September 2016]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/12387651
* ↑ Department of Health | Australia's Physical Activity and Sedentary Behaviour Guidelines [Internet]. Health.gov.au. 2016 [cited 27 September 2016]. Available from: http://www.health.gov.au/internet/main/publishing.nsf/content/health-pubhlth-strateg-phys-act-guidelines