During exercise the cardiovascular system is called upon to meet the increased needs of the body in many ways. The cardiovascular system rushes oxygen to hardworking muscles, returns used blood to the lungs to be re-oxygenated, and delivers fuel to the active tissues of the body. The cardiovascular system undergoes drastic changes during and immediately after intense exercise. Even more importantly, the cardiovascular system makes long-term and beneficial adaptations to the demands of a regular exercise regimen.
One of the short-term effects of exercise is an increase in your heart rate. Actually, you heart rate will begin to rise before you even start to exercise. Your brain realises you are going to work out and releases adrenalin to speed up your heart in preparation for the upcoming exertion. This is called "the anticipatory response." Heart rate will continue to rise in direct proportion to the intensity of exercise until maximum heart rate is achieved.
Stroke volume--the amount of blood pumped out of the left ventricle by each beat--increases by up to 80 millilitres per beat.
Cardiac output--the volume of blood the heart pumps in a period of one minute--increases from the typical 5 litres per minute, to up to 40 litres per minute, during strenuous exercise.
Short-term changes in blood flow. At rest, the muscles require only about 15 to 20 per cent of the total amount of blood circulating through the body. During exercise the hardworking muscles demand more oxygen from the cardiovascular system, up to 80 per cent. In response, blood is shunted away from the digestive organs, kidney and liver and redirected to the skeletal muscles. Blood flow to the skin also increases. The blood vessels serving the skin dilate to allow more blood to the surface of the body. This helps to cool the body down during exercise.
Your blood pH--the level of acidity in your blood-- becomes more acidic. Your body uses by-products of carbon dioxide to buffer the hydrogen ions in your bloodstream. Hydrogen ions are electrically charged particles in your body. The greater the number of hydrogen ions, the higher the acidity. Because you breathe faster during cardiovascular exercise, you expel carbon dioxide faster than you would normally. This gives the hydrogen ions time to accumulate.
Decrease in resting heart rate. Because the rigours of regular exercise require so much work from the cardiovascular system, sedentary periods become even easier for the heart by comparison. The heart eventually becomes more efficient, and no longer needs to beat as quickly to supply the body with blood while at rest.
Stroke volume increases at rest. Resting heart rate is able to slow down because the heart is now trained to pump a larger quantity of blood with every beat.
Improved circulation. In response to the need to supply the muscles with more oxygen during exercise, the body increases its number of capillaries, the smallest blood vessels in the body. Existing capillaries also open wider.
Blood pressure decreases by up to 10 mmHg. An mm Hg is a unit used for measuring pressure levels.
Blood volume increases. The body produces a greater number of red blood cells in order to keep the muscles supplied with oxygen during heavy exercise.
The cardiovascular system reaps a myriad of benefits from regular exercise both immediately and over the long term. Any form of aerobic exercise, from swimming and running to dancing or skateboarding, can help strengthen the cardiovascular system.
- Human Anatomy and Physiology: Marieb, Elaine N. and Katja Hahn: 2010.
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