Cardiovascular endurance is defined as the ability of the heart and lungs to provide blood and oxygen to meet energy demands. Energy demands range from a resting state to a more intense exercise or activity state. Blood and oxygen are provided through the circulatory system and respiratory system consisting of the heart, lungs and vessels. The heart works to pump blood and oxygen to body parts to meet the demand that the activity places on the body.
Function
The heart functions as a pump sending fuel in the form of blood and oxygen to body parts to function effectively. One heart beat consists of a relaxation, or blood-filling stage, and a contraction, or blood-sending phase. Heart rate is measured as the amount of heart beats per minute. Cardiac output, or total blood flow, is based on the heart rate, number of beats per minute, and stroke volume, the amount of blood in each beat.
Resting Effects
At rest there is a very low demand for blood and oxygen, resulting in a lower heart rate. The average resting heart rate is 70 beats per minute. Higher activity levels place a higher demand on body functions to meet increased energy needs. To meet the additional blood flow demand, heart rate and stroke volume must increase.
Increased Demand Effects
Increases in heart rate are needed to send more blood to the working muscles. Some blood flow is diverted to the skin, where the heat generated by the working muscles can be released. The increased blood allows more oxygen to be sent to meet higher demands. For every extra liter of oxygen needed, 5 extra liters of blood are needed. Energy demands are higher when activity involves upper and lower body muscles compared to activities using lower body muscles only.
Variations
Variations in heart rate levels with exercise are based on many factors. High-intensity exercise will increase heart rate levels more than low-intensity exercise. In order to be effective, cardiovascular endurance training must be performed at an intensity that increases the heart rate to a minimum of 60 percent of capacity. Trained exercisers will have smaller heart rate increases due to larger stroke volumes. Untrained exercisers will have larger heart rate increases due to smaller stroke volumes. Additional factors that increase heart rate with activity include aging, higher stress levels, higher body temperatures, illnesses and medications.
Considerations
In order to achieve cardiovascular endurance gains, increased heart rate levels must be reached. The range of increases is referred to as the training zone. Exercising in the training zone for 20 to 30 minutes three to four times weekly is recommended. Increases in cardiovascular endurance levels result in significant health and fitness improvements.
References
- "Human Anatomy and Physiology"; Alexander P. Spence & Elliott B. Mason; 1979
- "Exercise Physiology: Energy, Nutrition and Human Performance"; William D. McArdle, Frank I. Katch & Victor L. Katch; 1986
- "Personal Trainer Manual"; American Council on Exercise; 1991
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