The Circulatory System

Components of the Circulatory System

The cardiovascular and cardiopulmonary systems work to distribute oxygen and nutrients throughout the body. This system also helps to remove carbon dioxide and other metabolic waste from the cells of the body.

In addition to these main functions, these systems also help to control body temperature, form blood clots to prevent excessive bleeding, and protect the body against disease.

Here is how the three main parts of the systems work together:

Part 1: Heart

The heart is the pumping mechanism that provides for the blood circulation cycle throughout the body. Every system of the body requires oxygenated blood, including the heart. Blood will leave the heart oxygenated and return to it deoxygenated.

Part 2: Lungs

The lungs receive deoxygenated blood and reoxygenate it for another cycle through the body.

Part 3: Blood Vessels

Arteries are the blood vessels that carry oxygenated blood from the heart to all the body’s tissues. As this blood is continuously being used by the body’s tissues, it becomes increasingly depleted of oxygen.

Veins then carry this mostly deoxygenated blood back to the heart and lungs where it will again be oxygenated. This cycle is continuous as the arteries will again carry this freshly oxygenated blood back out to all the body’s tissues.

Heart

The heart is a muscular pump that provides the force necessary to circulate the blood to all the tissues in the body. 

Its function is vital because tissues need a continuous supply of oxygen and nutrients to survive, and metabolic waste products have to be removed. Deprived of these necessities, cells soon undergo irreversible changes that lead to death.

While blood is the transport medium, the heart is the organ that keeps the blood moving through the vessels. An electrical system controls the heart and uses electrical signals to contract the heart’s walls. When the walls contract, blood is pumped into the circulatory system. Inlet and outlet valves in the heart chambers ensure that blood flows in the right direction.

The normal adult heart pumps about five liters of blood every minute. If the heart loses its pumping effectiveness for even a few minutes, the individual’s life is jeopardized.

Structure of the Heart

The human heart is a four-chambered muscular organ, shaped and sized roughly like a closed fist with two-thirds of the mass to the left of the midline.

The heart is enclosed in the pericardium, a double-walled sac containing the heart and the roots of the great vessels. The great vessels are the large vessels that bring blood to and from the heart: superior vena cava, inferior vena cava, pulmonary arteries, pulmonary veins, and aorta.

The pericardium attaches the heart to the mediastinum (the central compartment of the thoracic cavity surrounded by loose connective tissue), gives protection against infection, and provides the lubrication for the heart.

Layers of the Heart Wall

Three layers of tissue form the heart wall. The outer layer is the epicardium, the middle layer is the myocardium, and the inner layer is the endocardium.

Epicardium

The epicardium is the smooth outer membrane of the heart that is primarily composed of connective tissue and functions as a protective layer.

Myocardium

The myocardium is the heart muscle and is also referred to as the muscular wall of the heart. Its muscle tissue is composed of striated involuntary muscle cells (myocytes and cardiac) that are connected and form the contractile pump that generates the heart’s blood flow. Myocytes are the muscle cells that make up the cardiac muscle.

Endocardium

The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels. The endocardium also provides protection to the valves and heart chambers.

Heart Chambers

The heart is the epicenter of the cardiovascular system, and it is divided into four separate chambers (1):

Upper Chambers

  • Right atrium: receives deoxygenated blood from all parts of the body, except from the lungs.
  • Left atrium: receives oxygenated blood from the lungs. 

Lower Chambers

  • Right ventricle: pumps deoxygenated blood to the lungs.
  • Left ventricle: pumps oxygenated blood throughout the body, except into the lungs.

Circulation of Blood Through the Heart

The Heart Map

The Heart Map explains the:

  • functional interaction between the heart and lungs circulation pathways of the blood through the heart and lungs
  • names of the heart chambers
  • blood oxygen level as it is received or exits each chamber

Quick Overview

  • The heart receives the deoxygenated blood and pumps it into the lungs to get oxygenated.
  • After oxygenation occurs in the lungs, the oxygenated blood is pumped back into the heart.
  • The heart then pumps out the newly oxygenated blood to be circulated throughout the body and all of its tissues.

More Detailed Map

  • After the blood has circulated throughout the body, it returns to the heart almost totally depleted of oxygen.
  • This deoxygenated blood enters the heart through the vena cava.
  • From the vena cava, the deoxygenated blood enters into the right atrium.
  • From the right atrium, the deoxygenated blood goes to the right ventricle.
  • From the right ventricle, the deoxygenated blood goes into the lungs.
  • In the lungs, the deoxygenated blood becomes oxygenated.
  • From the lungs, the oxygenated blood goes to the left atrium.
  • From the left atrium, the oxygenated blood goes to the left ventricle.
  • From the left ventricle, the freshly oxygenated blood is then pumped out of the heart and circulated throughout the body to replenish all the body’s cells.

Diagnosing Circulatory Sounds

Stethoscope

Stethoscope is a device used to listen to internal body sounds, such as the heartbeat as well as the passage of air through the lungs and sounds in the abdominal region.

Sphygmomanometer

Sphygmomanometer is a device, along with a stethoscope, that is used to measure blood pressure. The sphygmomanometer consists of a rubber bladder that is enclosed in a nylon cuff and connected to an inflating bulb. The blood pressure is read on the manometer.

Auscultation

Listening to bodily sounds by using a stethoscope. The most familiar uses are to listen to the heartbeat, lungs, and the sounds that are used to measure blood pressure.

Auscultation is also used for the purpose of listening to other sounds from within the body that are necessary to make a diagnosis.

Korotkoff Sounds

With the use of a sphygmomanometer, Korotkoff sounds are the sounds used to determine blood pressure. There are five different sounds as the blood pulsates through the brachial artery. Each of these sounds are referred to as a phase:

  • Phase I: The appearance of clear tapping sounds.
  • Phase II: The sounds become softer and longer.
  • Phase III: The sounds become crisper and louder.
  • Phase IV: The sounds become muffled and softer.
  • Phase V: The sounds disappear.

It is necessary to distinguish the sounds in order to determine blood pressure. Phases I & V represent the systolic blood pressure, and the diastolic blood pressure, respectively.

Blood Pressure

Systolic Blood Pressure

The pressure exerted by the blood on the blood vessel walls with each heartbeat.

Diastolic Blood Pressure

The pressure exerted by the blood on the blood vessel walls when the heart rests between beats. Normal blood pressure is 120 systolic over 80 diastolic, or 120/80. 

High Blood Pressure, or Hypertension

Interchangeable terms that apply when blood pressure is greater than 140 systolic over 90 diastolic, or 140/90.

Essential Hypertension

More than 90 percent of all high blood pressure (hypertension) has no known cause and is referred to as essential hypertension.

White Coat Hypertension

An increase in blood pressure that only occurs when a person goes to the doctor. This temporary elevation in blood pressure is related to anxiety and not to the condition of hypertension.

Pulse

Pulse is the rhythmic expansion and contraction of an artery caused by blood being forced through it by the pumping action of the heart.

Palpation

Palpation is the use of fingers at a pulse site to measure the pulse rate.

Carotid Pulse Site

Located on each side of the front of the neck, over the carotid arteries, just below the angle of the jaw.

Radial Pulse Site

Located on the wrists, over the radial arteries, just under the thumb.

Temporal Pulse Site

Located on each side of the head, on the temple directly in front of the ear, over the superficial temporal arteries and extended from the carotid arteries.

Apical Pulse Site

Located over the apex of the heart, at the lower left of the heart, its sounds are heard through a stethoscope.

Cardio Measurements

Heart Rate (HR)

Heart Rate (HR) is the number of times the heart beats each minute, also referred to as beats per minute or bpm.

Resting Heart Rate (RHR)

Resting Heart Rate (RHR) is the number of times the heart beats each minute when a person is completely at rest. The resting heart rate can only be determined after a person has rested quietly for at least four or five minutes, either sitting or lying down. The average resting heart rate is about seventy-two beats per minute.

Cardiac Output

Cardiac output is the amount of blood pumped by the heart each minute. The average heart pumps about one gallon of blood each minute.

Stroke Volume

Stroke volume is the amount of blood pumped by each ventricle each time the heart beats.

Ejection Fraction

Ejection fraction is the percentage of the total volume of blood in the ventricles that is pumped out each time the heart beats. 

The amount of blood that fills the ventricles during the rest period between heartbeats is not always completely pumped out during a heartbeat. At rest the ejection fraction is only about 50 percent, and during exercise the ejection fraction can increase up to 100 percent.

Oxygen Extraction

Oxygen extraction is the process wherein oxygen is removed from the blood to be used by the muscles. This removal of oxygen takes place in the capillaries of the muscles.

Blood Function

Blood acts as the body’s transport system and it has the ability to prevent its own loss by clotting. Adults have about ten pints.

With a resting heart rate, the heart pumps about ten pints per minute throughout the body. During exercise the heart may pump forty pints or more a minute.

Approximately half of the volume of our blood is made of cells. There are red cells (erythrocytes), white cells (leukocytes), and platelets (thrombocytes). The remaining volume of blood is called plasma (see next section).

One of the main functions of the blood is that its red blood cells contain the protein hemoglobin, which transports oxygen throughout the body.

Another important function of the blood is that its white blood cells have the ability to defend against viruses, bacteria, fungi, and parasites and therefore help to establish our immune system.

Blood stops bleeding (also referred to as clotting) and helps in the repair of damaged blood vessels. The substance in blood that performs these two functions is called platelets.

Blood Components

Platelets

Platelets are cells that circulate in our blood. When a person gets a cut or sustains an injury, these platelets bind together at the site of the damaged blood vessel and cause the blood to clot, which stops the bleeding. 

Platelets are created in the bone marrow, the same area for the production of red blood cells, and most of the white blood cells.

Plasma

Another important component of blood is plasma, which is about 95 percent water. It also contains salt, proteins, sugars, fats, and minerals.

Plasma serves many functions such as carrying nutrients throughout the body. It also carries away waste products, such as urea.

Additionally, each gland manufactures its own unique hormone to be used specifically for its intended organ. Plasma carries these hormones to their intended destinations.

Hemoglobin

Hemoglobin is a protein in red blood cells that contains iron, carries oxygen throughout the body, and is responsible for the red color of blood.

Red Blood Cells (Erythrocytes)

Red blood cells are the body’s most common type of blood cells and the primary method for transporting oxygen throughout the body. Red blood cells also transport carbon dioxide to the lungs for removal when you exhale. These cells also contain a protein called hemoglobin, described above.

White Blood Cells (Leukocytes)

A major component of our immune system, white blood cells help to defend the body against infection by protecting against disease. All white blood cells are produced in the bone marrow.

Types of Blood Vessels

Arteries

The largest blood vessels in the body. They carry oxygen-rich blood away from the heart to nourish all the tissues of the body. Arteries have muscular walls that help them push the blood throughout the body. They are much stronger than veins.

Aorta

The largest artery in the body, the aorta receives freshly oxygenated blood from the lungs via the muscular left ventricle of the heart, and then pumps that blood out to the entire body.

Coronary Arteries

Coronary arteries are the two vessels originating from the aorta supply all parts of the heart muscle with oxygen-rich blood.

Carotid Arteries

Carotid arteries are the main arteries that are located on each side of the neck, one on each side. They are one of the easiest places to feel a pulse.

Arterioles

As arteries get further from the heart, their sizes become smaller, and these smaller arteries are referred to as arterioles.

Capillaries

As the arterioles get even further from the heart, they become the smallest blood vessels (capillaries) that can carry oxygen-rich blood to the tissues of the body.

Pulmonary Arteries

Pulmonary arteries are the arteries that deliver deoxygenated blood from the heart to the lungs. They differ from the other major arteries whose purpose is to deliver oxygenated blood from the heart to the body’s tissues.

The main pulmonary artery comes out of the right ventricle of the heart and divides into the right and left pulmonary arteries, which enter into the right and left lungs.

Venous System

Venous system is the entire network of blood vessels that consists of the veins. They carry blood that is depleted in oxygen, and higher in carbon dioxide, back to the heart.

Vena Cava

Two very large veins that receive deoxygenated blood from the body and return it to the right atrium of the heart. The superior (upper) vena cava collects blood from the upper parts of the body, such as the head, neck, and arms.

The inferior (lower) vena cava collects blood from the lower parts of the body, such as the legs and abdomen area.

Veins

Any of a series of blood vessels from throughout the body that carry deoxygenated blood back to the heart. Veins have valves to prevent blood from flowing backward. Blood collected by the veins is somewhat higher in carbon dioxide than freshly oxygenated blood.

Venules

Venules are the thinner divisions of the veins.

Pulmonary Veins

These veins deliver oxygenated blood from the lungs to the left atrium of the heart. They differ from the other veins whose purpose is to deliver deoxygenated blood to the heart. The four pulmonary veins are:

  • the right superior
  • right inferior
  • left superior
  • left inferior

Vascular

A term that refers to blood vessels, or to a blood vessel system that also carries body fluids such as lymph throughout the body.

Avascular

A term indicating the existence of few or no blood vessels in a body system.

Therapeutic Angiogenesis

The use of genes to grow new blood vessels to repair or replace damaged blood vessels in the heart muscle.

Heart Healthy Exercise

Ergometer

Used to continuously measure and record both the amount of physical work done by the body and also the body’s response to that work. The amount of physical work to be done is predetermined.

The device continuously measures and records heart function, such as heart rate and heart rhythm as well as blood pressure.

It also measures and records the breathing rate and the volume of oxygen that is consumed.

Ergometers can be stationary bicycles, treadmills, or rowing machines and are primarily used for fitness and stress testing.

Cardio Endurance

  • Cardiovascular Endurance
  • Cardiopulmonary Endurance
  • Cardiorespiratory Endurance

These three exercise terms, typically used interchangeably, relate to the ability of the heart and lungs to deliver enough oxygenated blood to the large muscles so that they can produce the energy necessary for sustained motion.

The Capacity to Consume Oxygen

  • VO2 Max
  • Max Cardiac Output
  • Max Oxygen Extraction

These three technical terms are collectively known as the capacity to consume oxygen, which refers to the highest volume of oxygen that a person can consume during aerobic exercise.

VO2 Max

VO2 Max is the product of cardiac output and systemic arteriovenous oxygen difference during a peak exercise session. The most desirable intensity range for VO2 Max is 50–85 percent.

Max Cardiac Output

Max cardiac output is the amount of blood pumped by the heart each minute. The average heart pumps about one gallon of blood each minute.

Max Oxygen Extraction

Max oxygen extraction is the process wherein oxygen is removed from the blood to be used by the muscles. This removal of oxygen takes place in the capillaries of the muscles. A graded exercise stress test is used to determine a person’s precise maximum aerobic capacity.

Aerobic Training Guidelines (Beginners)

Intensity

Intensity is the effort required to perform an aerobic exercise. When using the Training Heart Rate Chart to calculate intensity, it should be the effort that falls within 60–90 percent of this chart.

In order to condition your heart, you must bring your heart rate up to an appropriate level and continue for an appropriate amount of time based on your level of fitness.

Frequency

Frequency means how often an aerobic exercise is performed. If you are a beginner, it is recommended that you start exercising at least three times per week. Gradually increase exercising to five to six times per week.

Duration

Duration is the time required to perform an aerobic exercise.If you are a beginner, it is recommended that you start with fifteen to twenty minutes of exercise per workout. Gradually increase to thirty minutes of exercise per workout.

Warm-Up

An aerobic warm-up should last from five to eight minutes, using the same muscles that will be used for the planned aerobic activity.

Stretch

Be sure to stretch the same muscles that will be used for the planned aerobic activity.

Aerobic Conditioning Exercise Program

The components of an aerobic conditioning exercise program must include a plan for the following:

  •  fitness goals
  • endurance objectives (strength objectives would be part of an anaerobic program)
  • a warm-up and cool-down
  • selection of the type of exercise
  • frequency of the exercise
  • duration of the exercise
  • intensity of the exercise
  • flexibility training
  • a progression plan
  • safety awareness

Aerobic Conditioning Progression Plan

Periodically, certain components of the exercise program must be reevaluated to ensure that the program reflects improvement. As an individual progresses, particular emphasis should be applied to increasing:

  • frequency of the exercise
  • duration of the exercise
  • intensity of the exercise
  • level of flexibility

Initial Conditioning Stage

This first stage is where the body prepares for an aerobic conditioning program and it lasts for approximately four to six weeks. It is suggested that a person in the initial conditioning stage use a beginner’s level in the following:

  • aerobic exercises
  • stretching
  • callisthenics

In the beginning, the exercise frequency should be every other day. The exercise duration (time) should be between twelve and fifteen minutes.

Note that the intensity level of normal aerobic exercise programs is within 60–90 percent of the maximum heart rate.

However, in the initial conditioning stage, it is recommended that a beginner start exercising conservatively at a maximum heart rate level close to the 60 percent range. This intensity may vary according to such factors as:

  • age
  • level of fitness
  • bodyweight
  • medical condition or numerous other factors

It is recommended that people over the age of fifty get the approval of their physician to begin a planned exercise program. Approval is also recommended for people of any age who have health conditions. 

Improvement Conditioning Stage

This second stage is where most of the aerobic conditioning occurs and it lasts for approximately eight to twenty weeks.

Exercise intensity, and duration increase more rapidly than in the initial conditioning stage. Frequency is increased to five times per week.

Maintenance Conditioning Stage

This third stage is where a person has met her fitness goals and seeks to maintain them. Periodic reevaluation is recommended. Exercise variations are helpful to ward off boredom and to maximize the effects of one’s exercise routine. The frequency may be increased to six times per week for the advanced exerciser.

Cardiorespiratory Training Methods

There are five basic types of cardiorespiratory training:

  • Continuous Training
  • Interval Training
  • Fartlek Training
  • Circuit Training
  • Aerobic Composite Training

1. Continuous Training

A method of training that maintains the level of intensity between 50–85 percent of maximal oxygen consumption. Continuous training is divided into two categories:

  • Intermediate slow distance, which is continuous aerobic exercise for a period of twenty to sixty minutes.
  • Long slow distance, which is continuous aerobic exercise for a period of more than sixty minutes.

2. Interval Training

A method of training that uses high levels of intensity interspersed with low levels of intensity in repeated intervals.

This type of training is especially beneficial for people who are just beginning an aerobic exercise program or those who have a low cardiorespiratory classification.

The reason is that it gives the individual an opportunity to recover during the low-level intensity spurts that are part of interval training. 

An example of interval training is bicycling for three minutes at a high intensity, immediately followed by two minutes at a very low intensity. This changeover can be repeated five to ten times in a workout session.

The number of times a person would repeat this method of switching from high level intensity to low-level intensity is determined by the level of fitness of the individual.

Also, the level of intensity used both at the upper end and the lower end is determined by the level of fitness of the individual.

3. Fartlek Training

A form of training similar to interval training. High intensity–low intensity intervals are not specifically measured, but instead are determined by how the participant feels.

4. Circuit Training

Strength training using approximately ten to twelve exercise machines that are designed to train the major muscle groups going in order from the larger muscle groups to the smaller muscle groups.

It is a time-efficient method that usually takes about twenty to twenty-five minutes and performed in rapid succession, adding some level of aerobic conditioning as well.

5. Aerobic Cross Training (Aerobic Composite Training)

An individualized aerobic training preference is useful in overcoming boredom and overtraining. Individuals use any variety of training methods, as well as any variety of intensities or aerobic training devices.

Generally done by individuals who are in the maintenance phase of conditioning. Training variations are unlimited and spontaneous, and an individual may alternate between two or more aerobic activities at different levels of intensity and with some discretion.

The changeover from one exercise to another helps to prevent overtraining to a particular muscle group and gives the body a more thorough muscular workout along with the aerobic benefits.

A typical example of a fifty-minute aerobic cross-training workout is warming up by jogging for fifteen minutes, then riding a bicycle at a high intensity for twenty minutes, and then gradually cooling down on a treadmill for another fifteen minutes.

Cool-Down

To reduce bodily risk after your workout, it is essential that you cool down your body for at least five to ten minutes by performing low level aerobic exercise. You can use any aerobic exercise machine, but gradually taper the intensity so that when you finish, your aerobic effort is equivalent to a very slow walk.

Benefits:

  • Reduces the possibility of blood pooling, a sudden drop in blood pressure, lightheadedness, dizziness, and fainting.
  • Reduces the possibility of muscle spasms and cramping.
  • Reduces the amounts of beneficial hormones such as endorphins that are produced from vigorous exercise.
  • It is very important to lower the amounts of these hormones to reduce the risk of cardiac rhythm irregularities.

MET System

The intensity of an exercise may be designed to conform to a desired percentage (between 50–85 percent) of an exerciser’s maximum oxygen consumption, which can also be described as the functional oxygen capacity (or VO2 max).

This is a technical system that classifies physical activities by metabolic equivalents, known as METs. One MET is equivalent to a person’s oxygen consumption at rest. This amount is about 3.5 milliliters of oxygen per kilogram of body weight per minute (3.5 ml/kg/min).

The amount of time a person stays on the bicycle or treadmill makes it possible to estimate and convert the maximum oxygen consumption to a MET equivalent.

The MET system is used to measure exercise intensity for any sports activity and to derive an approximate energy measurement for those sports activities.

Furthermore, the necessary data derived from stress tests may be described in MET values.

Rate of Perceived Exertion (A Scale to Assess Exertion)

This exertion scale was designed by Dr. Gunnar Borg is often referred to as the Borg Scale.

It assigns subjective numerical values that are used to perceive the rate of exertion. On the Borg Scale, the range is from six to twenty. 

As an example, a perceived rate of six indicates no exertion. A perceived rate of thirteen would indicate a more difficult rate of exertion, and a perceived rate of twenty would indicate maximal exertion.

Recently a new rating scale has been developed, and the numerical values are different. This new scale has a range from zero to ten. As an example, a perceived rate of zero indicates no exertion. A perceived rate of four would indicate a somewhat difficult rate of exertion. A perceived rate of ten would indicate maximal exertion.

Talk Test

By observing the required effort to breathe and the required effort to talk during exercise, a subjective level of exertion can be determined. This method is very helpful in determining a safety zone for aerobic activity.

To maintain this safety zone, exercisers should keep the intensity of the exercise at a level that enables them to speak and breathe with relative ease.

Maximum Heart Rate and Calculations

Maximum Heart Rate (MHR) Formula

  • MHR = 220 bpm – age

Training Heart Rate Range (THRR)

The accepted intensities for aerobic training. They should be between 60–90 percent of a person’s maximum heart rate (MHR), and are calculated to determine both the upper and lower age-related training heart rate.

Using the MHR formula is one of the safest ways to monitor a training program. People interested in fat loss should begin a program between 60–75 percent of their MHR.

In any aerobics exercise program, it is recommended that you consult a certified personal fitness trainer to determine your THRR. Many gyms have charts to assist in determining the appropriate range of intensity for each age group.

Calculations for Lower and Upper Limits of MHR

Lower Limit = MHR x 60 percent

Upper Limit = MHR x 75 percent

Calculation Example:

A fifty-year-old adult wants to train at the suggested rates of 60–75 percent of his maximum heart rate.

MHR = 220 bpm – age = (220 – 50) = 170

Lower limit is 170 x 60 percent = 102

Upper limit is 170 x 75 percent = 128

Therefore, the THRR for this fifty-year-old is between 102 and 128 beats per minute.

Maximum Heart Rate Compared to Aerobic Capacity

For comparison, it is necessary to know the relationship between maximum heart rate (60–90 percent) and aerobic capacity/maximum oxygen consumption (50–85 percent).

At almost all levels of submaximal aerobic exercise, the percentage of maximum heart rate does not equal the same percentage of aerobic capacity unless the Karvonen Formula (also known as the Heart Rate Maximum Reserve Method) is used.

Karvonen Formula

One of the most popular methods for calculating exercise heart rates. It is a more accurate method than the maximum heart rate for finding the training heart rate range for an individual wishing to perform aerobic exercises.

Though the Karvonen Formula is similar to the maximum heart rate method, it is not the same because resting heart rate (RHR) is calculated into the formula.

Karvonen Formula Calculations

Abbreviations used for the Karvonen Formula Calculations

  • MHR (Maximum Heart Rate) = (220 – age)
  • Workout Intensity = ideally 60–90 percent of MHR
  • RHR (Resting Heart Rate) = an average of 72 bpm
  • HRR (Heart Rate Reserve) = the MHR – RHR
  • Aerobic Workout Intensity = ideally 50–85 percent of MHR
  • THR (Training Heart Rate) = HRR x Aerobic Intensity + RHR

The desired intensities for the Karvonen Formula must always be between 50–85 percent.

Using the Karvonen Formula

Example

To use the Karvonen Formula to calculate a desired training heart rate, let’s assume:

  • the person is fifty years old,
  • with an RHR of 75 bpm, and
  • the desired intensity of 65 percent.

The Karvonen Formula is as follows:

  1. (MHR – RHR) = HRR
  2. HRR x Aerobic Intensity + RHR = THR

Explaining the four-step formula:

  1. Calculate the maximum heart rate (MHR), which is 220 – age.
  2. Deduct the resting heart rate (RHR), and that gives you the heart rate reserve (HRR).
  3. Multiply the HRR by the desired aerobic intensity. (It is very important that the intensity selected is between 50–85 percent).
  4. Add the RHR.

This gives you the desired training heart rate (THR).

Applying this to our example, the calculation looks like this:

  1. Calculate the maximum heart rate (220 – 50 = 170)
  2. Deduct the person’s resting heart rate (170 – 75 = 95)
  3. Multiply by the desired intensity (95 x 0.60 = 61.75)
  4. Add the person’s resting heart rate (61.75 + 75 = 137)

The desired training heart rate is 137 beats per minute.

How to Train Safely

The most important things to consider are the following:

  • The following suggestions are based on the Maximum Heart Rate (MHR).
  • Always consider your age, the length of time you have been training, your fitness level, and the condition of your health.
  • As a guideline for beginners in good health, select an aerobics exercise program that uses your maximum heart rate (220 – your age).
  • Using the calculation of the maximum heart rate from above, calculate heart rate intensities of 60 percent and 75 percent to determine the lower and upper limits for your aerobic workout.
  • If you are over age fifty, or have medical problems: consult your physician before starting your fitness program, or intensify your fitness program by moving up to the next higher level.
  • The primary goals of your aerobic training should be to improve your cardiovascular function and to burn calories.
  • In order to continually improve, you must attempt to increase both the intensity and the duration of the aerobic exercise program.
  • Once again, for beginners, once you have reached the recommended maximum heart rate of 75 percent, and can sustain that rate for at least 20 minutes, you should attempt to continue at that level for several weeks. Afterwards, consult a personal trainer for advice.
  • If you are in the intermediate stage as an exerciser, you may select a Training Heart Rate Range in accordance with your fitness level.
  • If you are a super athlete, you may train as high as 90 percent of the MHR for your age, however, you should first consult a personal trainer, or your physician, regardless of your age.
  • Caution, if you are not a professional athlete, you should never train at or near 90 percent of your MHR.

Circulatory System Injuries and Conditions

Heart Conditions

Arrhythmia

Any abnormal rhythm in the way the heart beats.

Bradycardia

The term used to describe a slow heart rate, one that is less than sixty beats per minute.

Tachycardia

The term used to describe a rapid heart rate, one that is more than one hundred beats per minute. 

An electrocardiogram (a line graph) shows changes in the electrical activity of the heart over time and is made by an instrument called an electrocardiograph. 

The graph can show that there are abnormal conditions, such as blocked arteries, changes in electrolytes (particles with electrical charges), and changes in the way electrical currents pass through the heart tissue. Also called ECG and EKG.

Aortic Stenosis

This condition is due to the narrowing of the aortic valve opening from the left ventricle of the heart.

Angina

Pain originating from the heart is usually caused by decreased blood flow through the coronary arteries supplying oxygen to the heart. It is also referred to as angina pectoris.

Ischemia

A localized deficiency of blood supply resulting from constriction or obstruction of the arteries.

This condition results in an insufficient supply of blood to a specific organ or to specific tissues. It is usually caused by atherosclerosis.

Arteriosclerosis

Thickening and hardening of the artery walls are caused by one or more of several diseases.

Atherosclerosis

A form of arteriosclerosis is characterized by the accumulation of calcium, cholesterol, and other fatty materials on the inner walls of the arteries causing them to harden, thicken and lose elasticity.

Coronary Artery Disease (CAD)

The specific condition of atherosclerosis is when it affects the coronary artery of the heart.

Myocardial Infarction (commonly called a heart attack)

The death of a section of the heart muscle occurs when a coronary artery becomes completely blocked. This blockage is usually caused by a blood clot in the coronary artery that has been narrowed by atherosclerosis.

Myocarditis

A condition that results in inflammation of the heart muscle. Occasionally, when an apparently healthy young person has died unexpectedly during participation in a sport, an autopsy reveals the cause of death to be myocarditis.

Blood Conditions

Anemia

A below-normal amount of hemoglobin, which is the oxygen-carrying pigment in the blood. Hemoglobin is found inside red blood cells and its purpose is to transport oxygen from the lungs to the tissues of the body. The most common type of anaemia is due to a deficiency of iron. However, there are many other types of anaemia.

Cyanosis

A bluish discoloration, especially of the skin and mucous membranes, is caused by reduced hemoglobin in the blood.

Hypercholesterolemia

Hypercholesterolemia is the term used to refer to high levels of blood cholesterol.

Understanding Cholesterol

Cholesterol is a soft, waxy substance that belongs to a family of fat compounds called lipids. It is manufactured in the body by the liver, and it can also be obtained from any food or drink that comes from animal sources (e.g., meat, poultry, fish, eggs, cheese, butter, etc.).

Other important characteristics are as follows:

  • Measurements are essential in helping physicians diagnose a person’s health.
  • Essential to life.
  • Always present in the blood and in all the cells of the body.
  • Unable to dissolve in the blood.
  • Transported throughout the bloodstream on substances known as lipoproteins.
  • Not found in fruits or vegetables or in any plant.
  • Has many functions, including the building of cell membranes, and the building of brain and nerve tissues.
  • Used to help the body produce steroid hormones, which are needed for body regulation, including the processing of food.
  • Helps the body produce bile acids, which are needed for digestion.
  • Required for other functions of the body’s chemistry. 
  • Cholesterol intake from foods should not exceed 300 milligrams per day.
  • Cholesterol is dangerous for the body only when it is present at unhealthy levels.

Cholesterol Terms

Lipoproteins

Particles of proteins, cholesterol, and triglycerides are combined by the liver. Their purpose is to transport cholesterol and triglycerides through the bloodstream, and therefore throughout the body.

HDL (High-Density Lipoprotein)

HDL protects the body by transporting cholesterol from cells in the arteries to the liver and other parts of the body for reprocessing or elimination.

HDLs contain more protein than fat and are referred to as the “good cholesterol” because of their ability to remove cholesterol from the cells in the arteries. This process helps to protect you from having a heart attack or stroke.

The higher your HDL, the lower your risk. The lower your HDL, the higher your risk.

LDL (Low-Density Lipoprotein)

LDL transports cholesterol from the liver for use by all the cells of the body. LDLs contain more fat than protein. LDLs are referred to as the “bad cholesterol” because they also cause buildups of plaque in the arteries by depositing harmful cholesterol on the artery walls.

The higher your LDL, the higher your risk. The lower your LDL, the lower your risk. Most of the body’s cholesterol is LDL cholesterol.

Triglycerides

The main type of fat consumed in the diet. Most of the body’s stored fat is in the form of triglycerides. Triglycerides are just one type of fat that is transported through the blood to be used by the body’s tissues.

Triglycerides are formed from three fatty acid molecules and one glycerol molecule. It is believed that triglycerides may be a risk factor for heart attack or stroke.

Total Blood Cholesterol

HDL + LDL + 20 percent of a person’s triglyceride level.

Lipids

A group of fatty substances that include cholesterol and triglycerides. Lipids are also vital nutrients that are a necessary part of every cell. They store energy, supply energy, protect internal organs, and carry fat-soluble vitamins.

Lipids are also characterized by the fact that they are insoluble in water.

Dietary Fat and Cholesterol Levels

Effects of Eating Less Cholesterol

Many people are confused about the effect of dietary fats on cholesterol levels. At first glance, it seems reasonable to think that eating less cholesterol would reduce a person’s cholesterol level.

Actually, eating less cholesterol has less effect on blood cholesterol levels than eating less saturated fat. However, some studies have found that eating cholesterol increases the risk of heart disease even if it doesn’t increase blood cholesterol levels.

Effects of Eating Good Cholesterol

Another misconception about cholesterol is that people can improve their cholesterol numbers by selecting foods that contain only “good cholesterol.” 

However, this is not possible. When we eat food, our bodies determine whether it will convert the cholesterol to the HDL (“good cholesterol”) or the LDL (“bad cholesterol”). We have no say in the matter! In food all cholesterol is the same. In the blood, whether cholesterol is “good” or “bad” depends on the type of lipoprotein that’s carrying it.

Dietary Cholesterol Requirements

People don’t need to consume any dietary cholesterol because the body can make enough cholesterol for all of its needs. 

The typical American diet contains substantial amounts of cholesterol, however, which is found in foods such as egg yolks, liver, meat, some shellfish, and whole-milk dairy products.

Cholesterol in Plants and Animals

The only foods that contain cholesterol are foods of animal origin. Plant foods do not contain cholesterol.

Blood Vessel Conditions

Aneurysm

Aneurysm is a bubble in a blood vessel that creates a weak spot in the wall of the vessel. The condition can be fatal if it ruptures. It is possible to have a genetic predisposition to develop aneurysms.

Stroke

Each of these three types of strokes is referred to as a cerebrovascular accident (CVA).

  • Cerebral Thrombosis: An impaired blood supply to the brain caused by a blood clot.
  • Cerebral Embolism: A ruptured blood vessel in the brain that had been weakened by a bubble in that vessel.
  • Cerebral Hemorrhage: A ruptured blood vessel in the brain.

Stroke Symptoms

  • Headache
  • Dizziness
  • Confusion
  • Visual disturbance
  • Slurred speech
  • Loss of speech
  • Difficulty swallowing
  • Range of Stroke Damage

Damage from a stroke ranges from unnoticeable, to mild or severe loss of bodily function (e.g., slurred speech, weakness or paralysis on one side of the body), to death.

Very often immediate emergency care in a hospital cannot only save the patient’s life, but it can also reduce the degree of damage.

It is of utmost importance that the patient is brought to a hospital within thirty minutes of experiencing symptoms to minimize the consequences.

Risk Factors For Stroke

  • Age
  • High blood pressure
  • Atherosclerosis
  • Heart disease
  • Diabetes mellitus
  • Smoking
  • Use of estrogen

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