During exercise, the muscles of the body require more energy and more oxygen than they do at rest. To supply the muscles with oxygen-rich blood, the cardiovascular system, has to make adjustments in how it meets your muscles' demands. To deliver the necessary oxygen and nutrients, your heart must adjust its pace to send blood through your body at a more rapid rate.
Oxygen is vital to all muscles of the body. The respiratory system is responsible for bringing oxygen into the body to be absorbed into the blood stream. The cardiovascular system then delivers the oxygen to your muscles. During exercise, the demand for oxygen increases because your muscles are working harder. In order to meet this increased demand, the heart has to pump faster in order to get oxygen out to them.
In order to accommodate for your muscles increased need for oxygen, your heart rate increases. Typically, the more intense the activity, the higher the heart rate. With vigorous exercise, or a cardiovascular stress test, your heart will reach a plateau which is called a maximum heart rate. For most people, that rate is 220 minus your age. Over time, the more conditioned you are the more efficient your heart becomes, and this increased efficiency will lead to a lower heart rate at rest. Your stroke volume, which is the amount of blood pumped out with each beat of the heart, increases as a result of cardiovascular conditioning. Additionally, during physical activity, your heart rate will not rise as quickly in a more conditioned person compared to a new exerciser. Another long-term effect of regular cardiovascular training is the increase in heart size. The left ventricle of the heart is the area that is most affected by training.
During exercise, the skeletal muscles are working harder and require an increase in the oxygenated blood. Your body adapts by sending more blood volume to those working muscles, and it does so by pulling blood flow away from the less active organs at that time. The less active organs are the liver, kidneys and intestinal tract. This is why it is recommended not to eat a large meal prior to exercise, since digestion will generate a competition for blood flow between the skeletal muscles and the gastrointestinal tract.
To accommodate for the increased need for blood and oxygen during exercise, the vessels of the cardiovascular system dilate, which is called vasodilation. Some of your capillaries, the smallest vessels, are also "activated." This activation of the capillaries and the vasodilation lasts several hours after exercise. Your blood pressure is the pressure of the blood on your arterial walls. During exercise, your systolic blood pressure should rise due to the increase in blood volume, while diastolic pressure should remain about the same. Because the vasodilation lasts for several hours after your workout is over, your blood pressure should be slightly lower than your resting value prior to exercise. This is why physicians often recommend physical activity as a means of controlling blood pressure.
The term body temperature in regards to exercise response must be broken down into two parts: core body temperature and skin temperature. The body works very hard to maintain a level core temperature, however during exercise, it does increase slightly. Sweating helps cool the body. As it evaporates, your skin and blood near the skin are cooled which helps maintain an ideal body temperature. The problem lies when exercising in a hot or humid environment where the skin can't cool or when sweat won't evaporate. In this environment, your temperature continues to rise which can cause overheating or even heat stroke.
- "Exercise Physiology: Theory and Application to Fitness and Performance," 6th edition; McGraw-Hill, Boston; 2007
- Sports Fitness Advisor: The Cardiovascular System and Exercise
- Creatas Images/Creatas/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.