Cardiovascular System

All the living organisms are formed of cells, that need oxygen to survive. The air enters in the lungs containing oxygen.The oxygen passes in the blood, where is carriyed through a system of ducts of various diameters named blood vessels.The cardiovascular system consists of the heart, the blood and the blood vessels( arteries, veins, capillaries, arterioles and venules), which facilitate the supply of oxygen and nutrients to cells and tissues.

The heart and the blood vessels

The heart is a pump, approximately the sixe of a man fist.It is situated in the thoracic cavity, behind the sternum and between the lungs; it's a bag of involuntary muscles. It has four chambers and muscular walls. Blood enters in the heart through large veins.When the heart contracts, blood is pushed throungh the arteries to the cells and tissues of the body. The flow of blood through the heart is facilitated by the contraction and relaxation of the heart muscle which is itself initiated by an electrical impulse.

Blood has three functions:

1. transporting oxygen and nutrients to the body cells and carrying of carbon dioxide to be expelled
2. plays an important role in the body's immune system, helping in the protection against disease
3. has an important role in the body temperature regulation, pH balance and water content of cells

The amount of blood pumped during one single contraction is called the volume of the beat. This volume is important like the heart rate. As the muscles need more oxygen, more the heart contracts. Consequently more blood is pumped out per minute (minute volume). However, as you improve your aerobic fitness, your heart will be more efficient and it's stroke volume increases; this way the heart of a well-trained person will beat slower; it still be able to send the same amount of blood to the working muscles each minute.

Anything that maintains the target heart rate 60% - 90% of the Maximum Heart Rate is considered aerobic.

The Maximum Heart Rate is determined by the participants age. This is the level that must never be exceeded. The MHR is determined as follows:

MHR = 220 - Age

The Target Heart Rate is the heart rate range that the participant should try to maintain during exercise. The participants fitness level determines which of the three intensity levels (beginner, intermediate or advanced) should be maintained.

There are 2 methods for calculation of the target heart rate. The Standard Method is the quick method and uses an intensity range of 60% to 90% of the maximum heart rate.

An example calculation using the Standard Method for a 30 year old for a desired aerobic intensity of 75% would be:

Standard Target HR = % intensity / 100 * ( Maximum HR )

Heart rate should be measured every 15 to 20 minutes for experienced participants of aerobic exercise, and every 5 - 10 minutes for beginner.

Pulse rate can be measured from one of two anatomical sites, the carotid artery or the anterior wrist.