VO2 Max is the most accurate measure of cardio-respiratory fitness. It measures the maximum amount of oxygen that the body can use in one minute per kilogram of body weight (mL/kg/min). During exercise, the heart rate responds by increasing, as does the delivery of oxygen to the body. Because of their dependent relationship, VO2 Max and heart rate are both valuable tools used to assess a person's level of cardiovascular fitness.
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The VO2 Max test is usually performed on a piece of cardio equipment, such as a treadmill or stationary bike. Exercise intensity and heart rate are increased gradually while oxygen and carbon dioxide present in the inhaled and exhaled air are measured through a breathing mask. VO2 Max is reached when the oxygen consumption levels off, despite continued increases in intensity.
Measuring heart rate and VO2 Max helps professionals to prescribe exercise safely and effectively to people of varying levels of fitness. These measures also serve as "an important tool in exercise training as part of a comprehensive cardiac rehabilitation," according to guidelines published jointly by the American College of Cardiology and the American Heart Association. Assessing cardiac function and oxygen consumption can be equally beneficial for novice exercisers looking to improve their health, trained endurance athletes looking to improve performance and people with heart conditions working to improve cardiac functioning.
"Studies show that you can increase your VO2 max by working out at an intensity that raises your heart rate to between 64 to 94 percent of its maximum for at least 20 minutes three times a week," recommends the American College of Sports Medicine. Those with a high VO2 Max will likely also have a lower resting heart rate, lower blood pressure and lower risk for chronic diseases, as these are also positively correlated with being fit.
In general, the higher the VO2 Max the better, but healthy ranges vary according to gender and age. A 25-year-old female with a VO2 Max of 36 ml/kg/min would be classified as having "poor" cardiovascular fitness, while a 65-year-old male with the same VO2 Max would be classified as having "good" cardiovascular fitness. Have a VO2 Max test done to gain a better understanding of your current level of fitness and work to increase your range if it needs improvement.
VO2 Max testing requires intense exercise that raises the heart rate extremely high to fully stress the body to its maximum limits. This is required to accurately measure the maximum amount of oxygen the body is actually able to utilize during exercise. Individuals, especially those with any existing cardiovascular or respiratory problems, should have the test performed under the supervision of a trained medical or fitness professional.