Aerobic fitness is a good measure of your heart’s ability to pump oxygen-rich blood to the muscles. Exercise scientists call aerobic fitness
“maximal oxygen uptake” and abbreviate it as Max. It is also called cardiovascular or cardiorespiratory fitness (CRF). Although there are technical differences among the terms cardio (heart), vascular (blood vessels), respiratory (lungs), and aerobic (working with oxygen), they all reflect various aspects of this component. A person with a healthy heart can pump great volumes of blood with each beat and has a high level of CRF.
Measures of Aerobic Fitness
Cardiorespiratory fitness values are expressed in the following ways: the number of liters of oxygen used by the body per minute (L/min) and METs. One MET describes the amount of oxygen used by the body at rest and is equal to 3.5 ml/kg/min. If you use 35 ml/kg/min during maximal exercise, you are said to have a CRF equal to 10 METs (35 ÷ 3.5 = 10). Because aerobic training programs increase the heart’s ability to pump blood, they result in increased CRF.
Most tests used to evaluate CRF use dynamic activities involving the large muscle groups in the legs (usually walking, running, stepping, or cycling).
Sequence for Testing and Activities
Generally, the testing process begins with a series of resting measurements, which may include a blood sample, a heart rate measure, a blood pressure measure, an electrocardiogram (ECG), pulmonary measures to evaluate lung function, and of course, a body fatness measure. The number and types of measurements will depend on your age, apparent health status, and your program facility (if any). Clearly, if you are exercising on your own, you are less likely to obtain sophisticated measurements prior to the tests. If you have a medical problem at high risk, you should have a physical examination prior to taking a test or starting an exercise program.
If the resting measurements indicate that you can take a test, a sub-maximal fitness test is generally recommended. Sub-maximal tests do not require you to exercise to your maximum effort, and they reduce the chance that you will have sore muscles the next day. Heart rate and blood pressure are usually measured, and the test is stopped at 70 to 85 percent of the estimated maximal heart rate. The results provide useful information related to your CRF and the test is a sensitive indicator of how you improve over time. In some testing centers, an ECG is also obtained, depending on the person being tested and the personnel involved.
If your measurements are normal, you are ready to start its program; if not, you may be referred for additional tests or procedures. In some testing centers the sub-maximal test is continued past this point, and you may be asked to exercise to the maximum. This is more likely in a clinical setting, where using this kind of maximal test increases the chance of finding any abnormalities. This type of maximal test is not recommended.