Exercise as it relates to Disease/How important is exercise duration, intensity & volume in the reduction of cardiovascular disease?

How important is exercise duration, intensity & volume in the reduction of cardiovascular disease?
Cardiovascular disease refers to any disease which affects the heart or blood vessels1. The main types of cardiovascular disease in Australia are coronary heart disease, stroke and heart failure/cardiomyopathy2. On average in 2016 one Australian died from cardiovascular disease every 12 minutes. Cardiovascular disease accounted for nearly 28% of all deaths in Australia in 2016. Regular physical activity has been shown to reduce the risk of cardiovascular disease mortality2. Exercise may have a positive effect on risk factors which contribute to cardiovascular disease including: reduction in both systolic and diastolic blood pressure, positive effects on lipid and glucose metabolism3. The aim of this study was to explore the importance of intensity and volume of physical activity when compared to cardiovascular disease risk factors as well as the importance of physical fitness relating to cardiovascular health.

Where is the research from?
This study was a part of the Utrecht Police Lifestyle Intervention Fitness and Training study, which was a fitness and lifestyle test for police officers from Utrecht, The Netherlands. The study was published by the European Society of Cardiology in 2009 in the European Journal of Cardiovascular Prevention and Rehabilitation. The researchers originated from Health and Lifestyle, Applied Psychology, Cardiovascular Disease and Rehabilitation Science faculties from Universities across The Netherlands and Belgium.

What kind of research was this?
The study was a voluntary, cross-sectional analysis3. The population was comprised of 1298 participants which included 874 men and 424 women. The age of the participants ranged between 18-623.

What did the research involve?
The research involved assessing the populations cardiovascular disease risk factors, the factors included: Central obesity (men: waist circumference > 102 cm; women: > 88 cm), high blood pressure (SBP > 130 mmHg and/or DBP > 85 mmHg), low HDL-cholesterol (HDL-C, men < 1.03 mmol/l; women < 1.30 mmol/l), high triglycerides (> 1.70 mmol/l) and high blood glucose (> 6.1 mmol/l) or being on drugs to treat any of these risk factors3.

Using the extended Adult Treatment Panel III (ATP III) criteria of the National Cholesterol Education Program ATP III definition4, the researchers defined if the participants had metabolic syndrome.

Participants were tested for VO2 Peak on bicycle ergometers at an initial workload of 20 Watts which increased at a rate of 20 W per minute until exhaustion. This test was used to assess their physical fitness. During the testing electrocardiogram and respiratory data were collected. Heart rate and Respiratory Exchange Ratio was some of the data this collection allowed for. Physical activity was assessed using a questionnaire. The question asked participants to report the average time and type of physical activity they undertook every week; these activities were given a metabolic equivalent value (MET). This data was then divided into three categories: PA MET-hours low (hours activities < 4 METs), PA MET-hours moderate (hours activities 4–6 METs), and PA MET-hours high (hours activities > 6 METs)3.

The methodology of comparing VO2 Peak to cardiovascular risk factors has validity as VO2 Peak is considered one of the gold standards of aerobic testing4, and by comparing these results with individual risk factors it can be ascertained which factors of cardiovascular health are most effected by physical activity and fitness.

What were the basic results?
The prevalence of metabolic syndrome in the population was 18.6%, and based on Adult Treatment Panel III criteria5, 58% of the participants were hypertensive. Dyslipidaemia was highly prevalent but only 5.5% of the population has abnormal glucose levels or were on drug treatment for glucose abnormalities.

In table 1 found in the article, there is a clear correlation between certain factors. The population were split into groups based on how many cardiovascular risk factors they possessed. As risk factors went up from 0 or to 3 or more, the participants on average: were more likely to be male, were older, had smoking currently or in the past, were heavier, had a lower VO2 Peak, spent less time performing physical activity and spent far less time performing high intensity physical activity when compared to those who had less cardiovascular disease risk factors.

High intensity exercise hours showed an inverse relationship with total cardiovascular disease risk. Some of the risk factors which inverse associations were found include: triglycerides, HDL-cholesterol and waist circumference.

Peak VO2 was also inversely associated with total cardiovascular disease risk, waist circumference, blood pressure, triglycerides, HDL-cholesterol.

What conclusions can we take from this research?
This study shows inverse relationships between physical activity levels, physical activity intensity, physical fitness and cardiovascular risk factors and metabolic syndrome. Exercise intensity and physical fitness appear to have the largest effects on cardiovascular disease risk factors.3

As there is a correlation between time spent completing high intensity physical activity and VO2 Peak, it can be assumed from this research that the more time spent completing high intensity activity, the higher the physical fitness of the participant.

As the amount of physical activity, the subjects were completing was ascertained on a self-report basis, it must be considered that there was likely some bias to reporting more a higher amount of physical activity and intensity performed than actual fact, but self-reported physical activity is still viewed to have adequate validity.6

Practical advice
The research gained from this study backs up the stance of the Australian Government that at least 300 hours of moderate intensity physical activity and 150 hours of high intensity physical activity should be performed7.

Based on this study, more of a focus on improving one’s physical fitness compared to complying with an amount of time to per day/week that one should complete.

Patients with high amounts of cardiovascular risk factors should be prescribed exercise carefully however, as heart disease, hypertension and diabetes can be contraindications for exercise when severe enough8.

With this in mind patients should be prescribed low to moderate aerobic activity that focusses on training large muscle groups and building their aerobic base to begin with. These patients should be monitored at all times and sufficient warm up and cool down exercises should be prescribed8.

As the patients continue with their program, progression should happen slowly as improvements allow8. Through this progression, testing of physical fitness could be useful for a practitioner to understand how much healthier the patient was becoming

Further information/resources
For further information or reading please find the links below

·        Sedentary lifestyle, poor cardiorespiratory fitness, and the metabolic syndrome (Lakka et al, 2003)

https://www.ncbi.nlm.nih.gov/pubmed/12900679

·        Cardiorespiratory fitness is inversely associated with the incidence of metabolic syndrome: a prospective study of men and women (LaMonte et al, 2005)

https://www.ncbi.nlm.nih.gov/pubmed/16009797

·       Physical activity in patients with cardiovascular disease: management algorithm and information for general practice

https://www.heartfoundation.org.au/images/uploads/publications/physical-activity-in-patients-with-cvd-management-algorithm.pdf