When you exercise, you have likely noticed that you begin to breathe harder and your heart beats harder and faster than when you are at rest. This increase in heart rate and the feeling of your heart beating harder combines to pump more blood throughout your body. The increase in blood movement results in an increase of oxygen movement throughout your body.
Cardiac Output
Heart rate is the number of times your heart beats in a minute, while stroke volume is the amount of blood your heart pushes out each time it beats. When you multiply heart rate by stroke volume, you get cardiac output, which is the amount of blood your heart pushes out each minute, notes the University of Montana Physiology Department. When you exercise, it is very common for cardiac output to increase.
Oxygen Consumption
Oxygen consumption is the amount of oxygen that is necessary for you to bring into your body to maintain normal function. When you exercise, your oxygen consumption increases, as your muscles are fueled by oxygen, according to the University of Montana Physiology Department. Oxygen is delivered to your muscles through the movement of blood throughout your body. As the demand for oxygen increases, your heart rate and stroke volume increase to bring more blood to your muscles.
Short-Term Response
Before you even begin to exercise, your heart rate increases in anticipation, which already increases cardiac output, according to Sport-fitness-adviser.com. This anticipatory response is caused by an increase in the neurotransmitters epinephrine and norepinepherine. Once you begin to exercise, your heart rate and stroke volume increase in proportion to exercise intensity. Increases in stroke volume will only increase by about 50 percent, notes Sport-fitness-adviser.com. Once stroke volume levels off, your heart rate becomes the limiting factor for cardiac output until you reach your maximum, steady-state, heart rate.
Long-Term Response
According to Sport-fitness-advisor.com, resting heart rate decreases while stroke volume increases, leaving resting cardiac output unchanged. During intense exercise, however, cardiac output increases dramatically with training. While maximal heart rate changes only slightly, maximal stroke volume increases significantly, accounting for the increase in exercise-induced cardiac output. As with any other muscle in your body, your heart becomes stronger and more forceful with training, which helps to propel more blood from the left ventricle with each beat.
Frank-Starling Mechanism
As you become more physically fit, the rate of blood return to the heart increases. This increase in the amount of blood filling your left ventricle causes it to be stretched farther than it would be if you had not been training. This increase in the ability of your heart muscle to stretch increases its contractile strength, pushing more blood out to your lungs to be oxygenated, says Richard E. Klabunde, Ph.D., associate professor of cardiovascular physiology at the University of Arizona. This increased stretching and harder contraction phenomenon is called the Frank-Starling Mechanism, after its discoverers.
Member Comments