Cardio exercise, also called aerobic exercise, is defined as exercise that uses your large muscle groups and that you perform for a minimum of 20 to create a sustained effect on your body's need for oxygen. The physical activities of running, jogging, swimming, cycling, and playing basketball are examples of cardio exercise.
Determining if You are Engaged in Cardio Exercise
Your normal heart rate is specific to you, but it is normally within the range of 60 to 80 beats per minute. Intense exercise will increase your heart rate. You will learn what your maximum target heart rate should be, based on your level of fitness and health. A much-used formula to determine your exercise target heart rate is to subtract your age from the number 220. For example, a 40-year-old woman would have a cardio exercise target heart rate of 180. If you are engaged in exercise that uses your large muscles for a sustained period of time and you experience an increased heart rate that reaches your target, you can assume you are performing cardio exercises.
Your Body's First Response to Cardio Exercise
The stages your body goes through during cardio exercise are directly related to how your body responds to your muscles' increased need for oxygen. A complex metabolic process called the Krebs cycle occurs in your body to create power to your muscles that don't normally store much energy. This biochemical process activates adenosine triphosphate at the cellular level to provide energy to your muscles.
More noticeable to you, there is an increased demand on your heart as it strives to provide more oxygenated blood to your muscles. First, your heart will beat faster to pump more blood. Second, as the blood is pumped through your heart, the left ventricle will pump more blood during each contraction. These two actions result in the total amount of blood that is pumped with each heartbeat to be larger than when you are resting. Third, this blood flow is directed to your muscles and away from other organs, such as your stomach. The blood also flows to the skin to increase heat loss and keep your body temperature regulated. These actions will increase your systolic blood pressure -- the top number of your blood pressure that reflects the contraction of your heart. Last, through mechanisms of osmosis between your vascular and non-vascular spaces, these actions result in your arterial blood having the ability to carry more oxygen.
Respiratory Response to Cardio Exercise
As your muscles require more oxygen, another of your body's natural responses is to obtain this oxygen by breathing more deeply or more quickly. As you breathe faster, you produce more carbon dioxide. Carbon dioxide, along with other complex mechanisms in the body, causes you to continue to breath faster to obtain more oxygen. This cycle continues until your oxygen needs reach a plateau or you slow down your exercise.
Long-Term Effect of Cardio Exercise
If you continue to engage in cardio exercise over a period of several months, the next stage your body will go through is improved fitness. Your heart becomes larger and stronger, your resting heart rate will decrease, your blood pressure can decrease and your skeletal muscle receives greater blood flow during exercise. These results will vary by an individual's overall health and level of fitness.
