Even at rest we all need of oxygen. The amount of oxygen we use at rest is the minimal level, comparable to all people and we can actually calculate oxygen use by multiplying 3.5 milliliter of oxygen by a persons weight in kilograms. This is definition of 1 MET. So, as an example, a 100 kilograms individual at rest is using approximately 350 milliliters each minute. The bigger you are the more oxygen you need but the formula works for all persons. 3.5 milliliter of oxygen times your weight in kilograms is 1 MET. So, the amount of oxygen each of us needs is dependent on your weight and the work being done. 

 

As we work, including grocery shopping, walking, raking leaves or running we use oxygen. How much? Well the more difficult the work the more oxygen needed. When we are just strolling we are at about 2 MET's. So, that 100 kg person is now using 700 ml of oxygen/minute while strolling. If we pick up the pace a little you are closer to 2.5 METs and when walking briskly you may be up to 3 METs. All tasks have a MET equivalent and with this equivalent you can calculate oxygen need. This defines intensity.

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You can also use METs Hours to define work volume. So, your wellness team might tell you that considering your current exercise behavior and fitness level you should shoot for 10 MET hours a week. This could be achieved by strolling, at 2METs for 5 hours a week (2x5=10) or maybe walking briskly, 3 METs for a little over 3 hours a week.

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Your MET maximum also tells us something about your current overall cardiorespiratory fitness (CRF). CRF is an independent predictor of mortality and morbidity risk. The higher your CRF the less risk. So, those in the lowest third of CRF for their age and sex have a 40% great chance of developing a comorbid condition and of death than someone in the top third for CRF of people their age and sex. This is a considerable risk. This is the same increased risk of death as smoking or being a type 2 diabetic. Having very good CRF is protective.

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Be sure to talk to your wellness team about classifying your MET max, your suggested MET levels during workouts and your suggested overall volume, MET hours, for each week.

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