Assessment of cardiorespiratory fitness is important for both athletes as well as the members of the general population. In athletes for apparent reasons. While in general population, VO2 max can be used to predict subsequent development of cardiovascular disease. Thus, VO2 max studies can be used for prevention, both primary as well as secondary, of development of cardiovascular sequelae like angina pectoris or myocardial infarction.
Furthermore, since cardiorespiratory fitness has been linked decisively to early deaths from a variety of causes, VO2 max studies in general population assume immense significance.
So what exactly is VO2 max? Well, in literal terms, it is the volume (V) of oxygen (O2) during maximum exercise that your body is able to transfer. As we all know, during exercise, your body needs energy and the chemical reaction to produce energy require oxygen (especially aerobic exercises). Thus, the higher your VO2 max,the more your body can transport oxygen effectively during times of intense training. Therefore, you will be able to train longer at higher intensity levels.
Methods of Assessing VO2 max
VO2 max can be measured using either maximal or sub maximal exercise testing protocols. Maximum exercise testing involves pushing the subject to the limit of intense physical exercise. So much so, that immediate medical attention is usually required. Maximal exercise testing is a true reflection of VO2 max. However, for obvious reasons, this method is best avoided, at least in the general population. Most authorities recommend the submaximal method (using submaximal loads of exercise intensity). Once the values are obtained using this method, regression equations are used to predict the actual VO2 max.
Whereas, maximal exercise testing is more sensitive, submaximal exercise testing is safer, esp. when implemented in members of the population who are not accustomed to training.
Maximal Exercise Testing:
Maximal exercise testing requires trained individuals and sophisticated equipment. Therefore, it is used only in certain clinical settings.
Submaximal Exercise Tests
Astrand and Rhyming Step Test: This test is carried out using a 33cm step/ aerobic bench for women and 40cm step for men. It involves stepping up and down the step or bench at the rate of 22.5 per min. ECG and steady state heart rate readings are taken. It would require 25.8 and 29.5 mL/Kg/min of oxygen uptake for women and men respectively.
YMCA step test and The Canadian Home Fitness Test can also be used for submaximal exercise testing. The step tests are popular because of use of minimal equipment and ease of implementation. Another major advantage is the minimal cost as well as the fact that large number of subjects can be tested at the same time as shown by The Canadian Home Fitness Test.
3 min. YMCA Step Test: This test determines how quickly your heart rate returns to normal after a bout of exercise. It uses a 12 inch aerobic bench. The subject steps onto the bench with a rate of 24 per minute (estimated oxygen uptake of 25.8 mL/Kg/Min.). After 3 min., the subject immediately sits down and the HR is counted for a minute. It is crucial that the HR is counted starting within 5 sec of stopping the exercise. The obtained HR values are then used to compare against established norms.
Treadmill Tests: A minimal of 3 min. treadmill test using 70% of heart rate reserve or and 85% of maximal heart rate as the end point of test is a better predictor of VO2 max than the step tests. Pretty much like in the step tests, achieving a steady state heart rate is imperative to get accurate data. Thus, the need to carry out the test for a minimum of 3min. Variety of treadmill test protocols are used: Bruce Protocol being the most popular of all.
Cycle Ergometer Tests
Astrand-Rhyming Cycle Ergometer Test: This is a 6 minute single stage test. The subject pedals at a rate of 50rpm to achieve a HR between 125 and 170 beats/min. HR should be measured during the 5th and 6th minute of the test. An average of 2 or more HR reading is taken and used to estimate VO2 max from Modified Astrand-Rhyming Normogram.
Other test like Maritz Test use a multi-stage cycle ergometer test to determine VO2 max.
A plethora of tests for assessing aerobic capacity are available. This, however, makes the choice of test to be used a bit difficult. A lot, however, depends on the subject, his/her cardiorespiratory status as well as availability of equipment and trained personnel.
At the end of the day, designing and implementing a good fitness program, either as a preventive measure for a cardiovascular disease or to achieve fitness goals is equally, if not more, important.