Exercise and Prevention of Heart Disease

Do not under-estimate the value of staying active, regular exercise can effectively help you evade the world’s biggest killer: Heart Disease. Let’s get to the bottom of this by exploring what the scientific community has established so far.

What is Heart Disease?

Heart Disease is a general term referring to a group of diseases which primarily affect the Heart and its related blood vessels. It is considered as part of a broader range of diseases affecting the heart and blood vessels in the human body, collectively known as Cardiovascular Diseases(CVDs). According the World Health Organisation, CVDs are the number one killer, accounting for over 17.9 million deaths in a year.

The commonest forms of Heart disease primarily affect the Heart muscle and its associated blood supply; ultimately leading to the hearts failure to pump blood to the whole body. These include Coronary Artery Disease and Ischemic Heart Disease.

Coronary Artery Disease

This involves compromised structure and function of the blood vessels which are responsible for supplying blood to the heart muscle, known as Coronary Arteries. Hallmark features of the disease include hardening and stiffening(loss of elasticity) of the vessels due to excess accumulation of fats on their walls.

This decreases the overall size/diameter of the blood vessel’s opening as well as their ability to adjust and accomodate the volume of blood needed for proper heart muscle function. Other causes of compromised coronary artery circulation exist. However, such cases are fairly rare. The majority of cases are due to long term deposition of fats in the blood vessels.

Ischemic Heart Disease(CHD)

Poor blood supply to the Heart muscle leads to a variety of disorders which are collectively known as Ischaemic Heart Disease. Prolonged deprivation of the Heart Muscle causes progressive injury, and may eventually lead to death of the involved heart muscle tissue. This is what’s commonly known as a “Heart Attack”, or Myocardial Infarction(MI) in medical terms.

From what we’ve considered so far, it’s easy to notice a direct relationship between the two diseases. In fact, over 90% of Heart Attack cases are caused by inadequate blood supply to the Heart muscle due to accumulation of fats in the responsible blood vessels.

Risk Factors of Heart Disease

Extensive research over the past few decades has shown that over 90% of Heart Disease cases are a result of a range of modifiable risk factors relating to lifestyle and personal habits. No wonder it’s considered a 21st Century lifestyle disease. Current literature has been able to identify 9 major risk factors namely:

Physical Inactivity

high intake of dietary fat

Obesity

High Blood Pressure

Smoking

Alcohol Abuse

Malutrition

Diabetes

Stress

Extensive studies conducted by Yusuf and colleagues provide further insight into how these factors account for the majority of cases. Striking observations were made based on data obtained from 29972 participants from all the major continents across the globe(52 countries). High concentrations of fats/lipids and smoking came out as the most significant factors, accounting for over 66% of the total risk of Heart Attack. Physical inactivity combines with the rest of the identified risk factors to contribute to about 90% of cases in males, and 94% in females.

Another observation worth noting is that these risk factors tend to interact in the development of the disease. This means that changing one risk factor may directly affect another. For example, changing physical activity levels may directly affect blood lipid/fat concentrations, which may in turn positively impact on the overall risk associated with the disease.

Grasping the relationship between exercise and Cardiovascular Disease means understating how Physical activity/exercise impacts on the key risk factors associated with the Disease. Let’s take a look at this based on what current research evidence suggests.

Physical activity and Cardiovascular Disease(CVD)

Scientific Investigations have consistently shown that individuals with higher physical activity levels have a lesser likelihood of developing Heart Disease. Most of these studies are based on observing the effects of exercise on biological substances and processes which are associated with increased CVDs. These include Cholesterol, Blood pressure, and a number of compounds and catalysts (Enzymes) which assist or hinder the processes which lead to undesirable changes in blood vessel structure and function.

Let’s have a basic idea on what these key processes involve before we move into how they are affected with regular physical exercise.

Blood coagulation: Involves formation of blood clots within blood vessels.

Fibrinolysis: Involves dissolution of an active substance called Fibrinogen in the formation of blood clots.

Vascular Remodelling: Structural changes in blood vessels.

Blood lipid profile: Concentration of different fat-based compounds in the blood.

The effects of physical exercise on blood coagulation and Fibrinolysis(refer to the above section for basic descriptions)

Coagulation and Fibrinolysis are the major processes involved in the formation of a blood clot. Generally, clot formation is a process that involves sticking together (aggregation) of blood. The key blood component involved in this are platelets.
This process isn’t all bad given the right circumstances. For example, it plays an instrumental role in healing, especially when it comes to closing a fresh wound to prevent further loss of blood. However, when it is consistently triggered within normal blood vessels, it can cause serious obstruction to the flow of blood.

A number of chemical catalysts(also known as Enzymes) within the blood interact to either facilitate or hinder clot formation. Let’s take a quick look at the most important catalysts. Don’t be intimidated by the fancy medical terms, you can forget them afterwards. The point of all this is to have a big picture on what goes on.

-Plasma fibrinogen: Facilitates clot formation.

-Plasminogen: Inhibits clot formation inhibiting Fibrinogen.

-Tissue plasminogen Activator(t-PA): Activates Plasminogen, or works together with the plasminogen to stop clot formation.

-Plasminogen Activator Inhibitor(PAI-1): Facilitatates clot formation by opposing the action of t-PA

From what we’ve considered, it should be easy to come down to two conclusions.

More Fibrinogen and PAI-1 means greater risk of blood clot formation. On the other hand, more Plasminogen and its activator means reduced risk.
Normally, there is a good balance between these factors. In fact, imbalances which favor clot formation are linked to most cases of Heart Disease and Stroke.

Now here’s the good news: Studies have been able to show a positive effect of exercise on fibrinogen concentrations, which are key in the formation of blood clots.

A good example is a large scale study conducted by El-Sayed, which reported significant reductions of fibrinogen concentrations following a period of a moderate-high intensity aerobic exercise program. The study used 30-minute exercise sessions at a training intensity of 75% of the maximum effort.

The conclusions made by these studies support findings form other ground-breaking studies done by the likes of Wang, Womack and De Souza. Wang observed that the ability of platelets to aggregate decreases in the long term following involvement in aerobic exercise programs. The 8-week program consisted of moderate intensity levels(60% of Maximum exertion), 30 minute-sessions, spread over 5 days a week. The study went on to demonstrate this effect further by showing that platelets aggregation capacity returned to previous levels after the participants stopped the training program.

Exercise and vascular remodeling

As described earlier, Vascular Remodelling involves structural changes that take place within the blood vessel walls, either to the benefit or disadvantage of blood supply to the target tissue.

Research seems to support the understanding that exercise has the capacity to improve blood circulation and hence supply to the heart muscle through a number of mechanisms. Blood flow and supply can be improved through formation of new blood vessels, modification of old vessels, and increased concentration of cells which facilitate formation of new blood vessels.

A number of studies have so far demonstrated the association between exercise and these factors. Studies done by Miyachi and colleagues furnish a good example. Following a period of aerobic and endurance exercises, the researchers reported notable changes in the major blood vessel that directly takes blood out of the heart to supply the whole body, known as the Aorta.

In trained participants, the vessel had increased in size(Diameter) by up to 26% along its descending course. This suggests a potential remodellig effect related physical exercise. Dineno and colleagues conducted one of the largest studies, which looked at the effect of exercise in 108 participants. After the training period, there were significant differences between the exercisers and the inactive group in terms of blood vessel size. The average size of the Femoral Artery(major artery that takes blood to the legs) was significantly higher in the regular exercisers.

This has a significant implication as far as normal blood flow is concerned in the body. There is much less resistance to blood flow which decreases the chances of high blood pressure and abnormalities associated with the blood vessel walls.
Bottom-line: Both the theoretical foundation and current evidence support use of regular exercise for the prevention and possible treatment of Ischemic Heart and Cardiovascular disease.

Exercise and Blood Lipid Profile

In layman terms, Lipids are generally known as Fats. There are different classes of Lipids based on composition. Lipoproteins are a class of lipids that draws interest from prominent researchers due to its relationship with Cardiovascular diseases. In general, these compounds are not purely fats, but rather a combination of fatty molecules and Proteins hence the name.

Lipoproteins are further classified based on the amount of associated protein present in their molecules.

– High Density Lipoprotein(HDL)

– Low Density Lipoprotein(LDL)

Low Density Lipoproteins have a higher fat component relative to the Protein, hence they are nicknamed “Bad Cholesterol”. Blood LDLs tend to accumulate in blood vessel walls, where they may react and trigger formation of fatty deposits called “plaques”.
These may in turn obstruct blood flow, or be dislodged to block smaller areas in critical organs such as the Heart or Brain. High Density Lipoproteins are called “good Cholestrol” for a good reason. They clean up the LDLs from the blood vessels before they are cleared to the liver where they are broken down.

According to scientific studies, Physical exercise has been shown to have a positive effect on the concentrations of both High and Low density Lipoproteins.
For instance, Izquierdo and team studied the effects of aerobic exercise on Lipid concentrations with favorable results. After an aerobic exercise routine targeting 2000kcal per week, there was a significant reduction of LDLs ad Cholesterol while HDLs concentrations took an upward turn.

This is a ground-breaking finding as far as Heart Disease Prevention is concerned due to the fact that Blood lipid concentrations are part of the 2 major factors that account for 66% of the contribution of modifiable risks factors.

Exercise and Blood Pressure

High blood Pressure is one of the most common Cardiovascular disease. The condition is also a predisposing factor to the development of Heart Disease. Physical exercise has become a huge part of treatment as it has been consistently linked with positive effects by decades of comprehensive scientific research.
Aerobic exercise has long been associated with successful reduction of Blood Pressure. Studies have so far reported reductions of up to 8mmgh in Systolic Blood Pressure, and 6mmhg in Diasttolic Blood Pressure respectively. Take a look at our article on exercise and High Blood Pressure for a more in depth discussion.

Conclusion and Recommendations

The value of regular exercise in the prevention of Heart Disease is apparent. The research evidence is rather overwhelming, thus justifying it as a huge part of our lifestyle. The good news is that you don’t have to be a gym freak to attain these health benefits. Moderate intensity aerobic exercises are enough as long as you stick to the recommended guidelines.
According to the ACSM, 150 minutes of moderate aerobic activity per week are adequate for the observed health benefits. Aerobic exercise involves repetitive physical activities such as brisk walking, running, swimming and cycling. Numerous studies have shown that exercising at a rate as low as 40% of your maximum Heart Rate for 20-30 minutes per session can produce tangible results. We’ve covered all the elements of effective aerobic exercise in the our aerobics article(coming soon).

Stay active! Stay active! Work hard! Work smart!