The human body is an exceptional piece of organic engineering. We have developed over thousands of years to reach our current physiological state. The cardiovascular system is a powerful system that helps feed our organs; muscular system, brain, and works together with our respiratory and nervous system. For our body to maintain exercise, cells of the body require a continuous supply of nutrition and the removal of waste products. The circulatory system provides this capability. Personal Trainers and fitness instructors can have a direct impact on this system. Culturally we have termed rhythmic aerobic training as “cardio” after the cardiovascular system. We have all forms of cardiovascular exercise options that will help keep the system healthy or tune the system for peak performance in sports.

While you study to become a level 3 personal trainer or level 2 gym instructor you will learn about the system; its structures, functions, and how to train the system. Writing fitness programs as a fitness instructor or periodised training plans as a fitness trainer is the creative part of the job, to do this you must have a thorough understanding of the system to write effective programs that are both safe and appealing.

Important Note: The cardiovascular system has three main sections, the heart, the blood vessels and the blood that flows through them. Let’s look at each section in more detail:

The Heart

Our heart is a powerful pump, designed to push oxygenated blood around the body to working muscles and deoxygenated blood to the lungs for the removal of carbon dioxide and recharging blood with oxygen.

The heart is divided into a “left” and “right” side with each having its own function. The right hand side is responsible for pumping oxygenated blood to the body. The left hand side is responsible for pumping deoxygenated blood to the lungs.

The heart has four chambers, the smaller chambers called the atriums are on the top and the larger ventricle chambers are on the bottom. The atriums sit on top of the ventricles and are connected by “non return valves”. The Atria (plural for atrium) “receive” blood from the body and the ventricles “pump blood” to all major organs and muscles.The septum separates the heart down the middle into its left and right sides.

The muscular tissue of the heart is called cardiac muscle also known as the myocardium (myo refers to muscle and cardium refers to the heart). 

Valves of the Heart

There are three main sets of valves that prevent blood from flowing backwards. The bicuspid valve is located between the right atrium and right ventricle. The “Tricuspid valve is located between the left atrium and left ventricle.

Note: Bicuspid and tricuspid valves are also known as atrioventricular valves.

We have semilunar valves located where the aorta leaves the left ventricle (to the muscles and organs) and another where the pulmonary artery leaves the right ventricle (to the lungs).

There are 3 classifications of blood vessels that connect the heart to our organs and muscles.

Arteries: Carry blood away from the heart under higher pressures. They have thicker walls and smaller internal diameters

Veins: Have thinner external walls than arteries with a wider internal diameter, they carry blood under lower pressures and have non return valves to stop blood flowing backwards.

Capillaries: Are the smallest of the blood vessels, being only one cell thick, they form networks around our organs and muscles for the diffusion of oxygen; carbon dioxide, and nutrients.

Note: Blood vessels get smaller the further they are away from the heart, the network of blood vessels connect via the following sequence: arteries; arterioles, veins, venules, capillaries. As blood returns to the heart this pathway reverses: capillaries; venules, veins, and arteries.

Four main blood vessels act as the plumbing of the heart to the lungs; organs, and working muscles.

Pulmonary artery – supplies deoxygenated blood to the lungs from the right ventricle.

Vena Cava – returns deoxygenated blood from the muscles to the right atrium. This is the main vein

Aorta – supplies oxygenated blood from the left ventricle to the working muscles. This is the main artery

Pulmonary vein – supplies oxygenated blood to the left atrium from the lungs.

Important note: typically, arteries carry oxygenated blood away from the heart and veins carry deoxygenated blood to the heart. The exceptions are the pulmonary artery which carries deoxygenated blood and the pulmonary vein which carries oxygenated blood to the heart.

Coronary Circulation

Like all other muscles, the heart requires its own supply of blood to continue working. This is specifically known as “coronary circulation”.

The heart receives a supply of blood from the left and right coronary artery. These two coronary arteries branch off from the base of the aorta just below the exit of the left ventricle. The two arteries subdivide into smaller blood vessels to supply the entire heart with blood. The right coronary artery mainly supplies the myocardium (heart muscle). The left coronary artery divides into two branches to supply the left ventricle and the posterior side of the heart. The coronary arteries divide into a network of blood vessels to provide blood to the entire heart and have built in fail safes. If one vessel becomes blocked or narrowed due to heart disease another healthy vessel can usually supply blood.

Pulmonary & Systemic Circulation

There are two sides of the cardiovascular system, each deals with its joint functions as above with its own specific function. The left side “systemic circulation deals with pumping and supplying oxygenated blood to the organs and muscles, while the right side returns deoxygenated blood back to the lungs for replenishing oxygen levels and removing waste products.

Sinoatrial Node

A very important part of the cardiovascular system, the sinoatrial node is part of the autonomic nervous system. The (SA node) stimulates the heart to contract with an electrical impulse without conscious thought to maintain blood flow and (life). The heart is stimulated around 72 beats per minute for normal activity. This changes with exercise and other internal and external factors. The Sinoatrial node is a complex set of cells located in the upper wall of the right atrium.

Blood Pressure

Blood pressure is the measure of force that blood applies to the internal walls of arteries. Blood pressure (BP) is measured in millimeters of mercury (mmHg). Optimal blood pressure is 120/80 mmHg. The first number (120) represents systolic blood pressure and the second number(80) represents diastolic blood pressure.

Systolic Blood Pressure: provides a measure of force that blood supplies to the internal wall of an artery during the contraction phase of a heartbeat. This number is higher due to the increase in blood volume entering the systemic circulation system from the left ventricle with each heartbeat.

Diastolic Blood Pressure: is the measure of force that blood flow applies to the internal wall of the arteries in the relaxation phase of the heartbeat. This phase is known as diastole to allow blood to be sucked into the atria to refill the chambers with blood before the next contraction. Diastolic blood pressure is always the lower reading.

Measuring the Performance of the Heart

The primary function of the heart is to pump blood. The heart is our engine and its performance can be measured. Performance of the heart is measured by calculating the amount of blood flowing out of the heart every minute (cardiac output). Cardiac output is a measure of heart rate multiplied by stroke volume.

Cardiac output: Amount of blood leaving the heart every minute, measured in millilitres Heart rate: Number of heart beats every minute, measured in beats Stroke Volume: Amount of blood leaving the heart every beat, measured in millilitres.

The maths: cardiac output (Q) = heart rate (HR) x Stroke Volume (SV)

Typical values at rest and during exercise

Cardiac output at rest: (Q) = (SV) 70 x (HR) 70 = 4900ml/min or 4.9 l/min

Cardiac output during exercise: (Q) = (SV) 120 x (HR) 180 = 21600ml/min or 21.6 l/min

During exercise cardiac output increases due to the body’s demand for oxygen, increased energy requirements and to remove increased levels of waste products. Regulating Body Temperature

In hot environments blood vessels close to the surface of the skin become larger, this process is called vasodilation. This allows heat to be released through the skin. In the cold, the blood vessels do the opposite, they get narrower, known as vasoconstriction. This maintains our internal body temperature for survival in cold environments.


Blood plays an important role within the cardiovascular system, it is the transport vehicle for oxygen and other materials around the body and helps fight against infection. Blood contains;

Red blood cells – transport oxygen White blood cells – protect against disease and infection Blood Platelets – help the blood clot and heal cuts Plasma – carries the above cells and transports important nutrients

4 Functions of the Cardiovascular System

The cardiovascular system has specific functions and they are to;

Transportation of oxygen; hormones, and nutrients Remove waste products that includes lactic acid and carbon dioxide; Protection against disease and infection; Maintain body temperature.

Effects of Disease on Blood Vessels

Vascular disease is the reduction of blood flow to the heart and body by a narrowing or hardening of the arteries, reducing their ability to supply blood. Reduction in blood flow to the heart known as (ischaemia) is a result of heart disease.

Heart disease also known as vascular disease is a result of mineral, protein and fat deposits within the artery walls. This build up narrows the artery walls and is known as atherosclerosis.

Remember that blood vessels are made of smooth muscle, if the artery wall becomes inflamed or damaged through poor health, diet or lifestyle. These deposits get caught and build up inside the artery wall. The body will attempt to fix the damage with cholesterol, protein and mineral deposits. As these build up they form a plaque that hardens the artery wall; thickens the internal diameter of the artery, and make it less elastic. This makes an artery less responsive and able to stretch as blood flows through it. The hardening of the artery is known as arteriosclerosis

Imagine the drain connected to your sink, when you wash the dishes you are cleaning the leftover food from the dishes into the sink. These left over fatty bits once stuck to your plates are now being washed into the drain. If you wash too much fatty leftovers into the drain over a long period of time, these deposits will build up and block the drain, forcing you to clear the drain so that water can flow though it again. This is exactly what happens when deposits build up in the artery wall. Except they are a little more tricky to fix.

Note: Atherosclerosis is a narrowing of the artery wall and atherosclerosis is a hardening of the artery wall. Coronary disease specifically affects the coronary arteries supplying blood to the heart. Ischemia is a reduction in blood flow (inadequate flow) to organs; muscles, and the heart. A combination of hereditary genes; lifestyle factors, family history, lack of exercise, stress, unhealthy diet, being overweight, alcohol consumption, and smoking can cause the gradual onset of atherosclerosis and arteriosclerosis resulting in (coronary and cardiovascular disease).

Cardiovascular Benefits of Endurance Training

Short Term changes During Exercise These represent the body’s attempt to supply more blood around the body to cope with the physiological response to heart rate, changes include;

  • Increased heart rate
  • Increased stroke volume
  • Increased blood pressure
  • Increased cardiac output

Long Term Benefits of Exercise

After a period of increased physical activity levels and exercise the positive changes in cardiovascular function can improve the efficiency of the heart and vascular system to pump blood around the body. During exercise this will be displayed as a lower working heart rate, increased stroke volume and increased cardiac output. Essentially providing (more power with less stress on the heart). During a resting state we will see a lower resting heart rate; lower blood pressure, and a greater stroke volume.

The main adaptations to long term exercise include:


  • Increased stroke volume
  • Increased strength & elasticity of arteries
  • Increased levels of good cholesterol (HDL)
  • Increased blood supply
  • Increased haemoglobin in the blood (increased oxygen carrying capacity
  • Increased capillary density
  • Increased aerobic capacity


  • Decreased blood pressure
  • Decreased levels of bad cholesterol (LDL)
  • Decreased resting heart rate

Decreased Risk of Chronic Disease: – Decreased risk of heart disease – Decreased risk of obesity – Decreased risk of type 2 diabetes


Our cardiovascular system is an organic mechanical system that keeps our body running. We feed the digestive system with fuel and the cardiovascular system transports that fuel to our organs and working muscles via blood. We are able to fight infection from the transport of white blood cells through our body, and maintain our body temperatures from changes in internal and external environments. Blood plays an important role in transporting oxygen; hormones and nutrients to maintain normal bodily functions while aiding the removal of waste products.

As a physiological piece of engineering the cardiovascular system should be cared for, we need to keep it healthy through physical activity; exercise, a balanced happy lifestyle, avoid long term stress, and ensure the levels of cholesterol, LDL, and HDL are balanced to avoid long term chronic disease. Personal trainers and fitness instructors must understand the importance of the cardiovascular system and how it functions to support clients with long term health or strength and conditioning goals.

To learn more about the cardiovascular system and its relation to exercise. PT Skills Academy delivers fitness instructor courses, and personal trainer courses via online learning and practical fitness coaching. We deliver online personal training courses in Leeds, our fitness instructor course is a prerequisite qualification for the personal training course. We also provide specialist cpd awards for our learners to specialise as fitness instructors in kettlebellcircuit and suspended movement training.

To learn more about how to become a personal trainer, please enquire with our enrolment team.