What is 'VO2 max' and how does it Measure Cardiovascular Fitness?

One way to determine how fit you are is to measure how much oxygen your body can efficiently consume-a measurement of how hard your muscles are working. Your VO2 max is the measurement of how much oxygen you consume in a minute, while exercising at sea level.

The greater your oxygen consumption, the better your cardiovascular health. Hospital fitness programs measure a person’s VO2 max by having a person exercise under conditions that push the heart’s ability to deliver blood to its maximum.

For instance, you might run on a treadmill that increases in speed and/or steepness at regular intervals. While you are exercising, you breathe out through sensors that measure air volume and oxygen concentration.

Computer analysis determines how much oxygen your body is using. As the workload increases, so does your oxygen consumption-up to a point. At the point, exercising harder shifts the muscles to the anaerobic activity. Soon after this point, the muscles will fatigue and you will have to stop exercising.

VO2 max can be expressed as an absolute number-the number of liters of oxygen a person consumes in a minute. Or it can be expressed as a relative number-the number of milliliters (ml) of oxygen a  person consumes in a minute divided by the person’s weight in kilograms.

The average relative VO2 max of an untrained man in his mid-30s ia about 40≠45 ml/min/kg. After an endurance exercise pro-gram, that same man might have a VO2 max of 50≠55 ml/min/kg.