# How VO2 Max Works

## Calculating VO2 Max

To understand the VO2 max formulas, let's first look at VO2, or the difference between the oxygen you breathe in and the amount you breathe out. The difference in oxygen levels between the air you inhale and the air you exhale indicates how much oxygen your body is using. You can calculate VO2 using the following formula:

VO2 max = maximum milliliters of oxygen consumed in 1 minute / body weight in kilograms

VO2 is measured in liters of oxygen consumed per minute and may be expressed in units of liters per minute (liters/minute). Your VO2 max is the maximum amount of oxygen your body can use. Since your body weight is used as part of this measurement, the units used are typically milliliters/kilograms/minutes. The following is the basic formula for calculating VO2 max:

VO2 = (milliliters of air inhaled per minute)(percentage of oxygen in the air inhaled) / (milliliters of air exhaled per minute)(percentage of oxygen in the air exhaled)

Do you know the maximum milliliters of oxygen you consume in a minute? Probably not. You can have this measured professionally at some medical facilities and training centers. The test typically involves breathing into an oxygen mask while walking on a treadmill at a certain pace for a certain amount of time. However, this test may be too expensive for the average recreational runner. Because of this, physiologists and sports scientists have devised other formulas you can use to calculate your VO2 max, using factors such as your age, resting heart rate, and maximum heart rate. [source: Plowman and Smith]

Here are two of these alternate formulas for calculating your VO2 max:

Using your resting heart rate and age:

VO2 max = 15.3 x (MHR/RHR)

MHR = Maximum heart rate (beats/minute) calculated using age = 208 - (0.7 x age)

RHR = Resting heart rate (beats/minute) = number of heart beats in 20 seconds x 3

The Rockport Fitness Walking Test (RFWT) using a 1-mile (1.6-kilometer) walk:

VO2 max = 132.853 - (0.0769 x W) - (0.3877 x A) + (6.315 x G) - (3.2649 x T) - (0.1565 x H)

W = Weight (in pounds)

A = Age (in years)

G = Gender factor, G = 0 for females and G = 1 for males

T = Time to complete the 1-mile walk (in minutes)

H = number of heart beats in 10 seconds at the end of the 1-mile walk

Other VO2 max formulas use data from a 3-minute step test or from a 1.5-mile (2.4-kilometer) run-walk test. You can find these formulas along with quick VO2 max calculators online.

Now that you know how to get your VO2 max number, what does it mean? Are you just average, or are you destined to be a world champion? Go on to the next page to find out how to use your VO2 number and ways you can increase it.