The intensity of physical activity can also be estimated by using the metabolic equivalent (MET) scale. Metabolic equivalent is the ratio of the work metabolic rate to the resting metabolic rate. One MET equals the expenditure of 3.5 milliliters of oxygen a minute for each kilogram (2.2 pounds) of body weight. This approximates the energy cost of sitting quietly.

The harder the body works, the higher the MET level. For example, a 5 MET activity such as cleaning gutters uses about five times more energy than sitting still.

An extensive chart called "The Compendium for Physical Activities Tracking Guide" lists the METs used for hundreds of leisure, work, household and other activities, everything from dancing the mambo (3 METs) to making maple syrup (5 METs) to mowing a lawn (5.5 METs).

Moderate activities are broadly described as 3 to 6 METs, while vigorous activities are classified as greater than 6 METs. Many activities are broken down to detailed levels of exertion. For instance, bicycling 10 to 11.9 miles per hour (mph) uses 6 METs, and bicycling 16 to 19 mph uses 12 METs.

A physician may advise patients to avoid overexertion by limiting activity to a certain MET level. These individuals would be given a copy of the chart. The MET scale is used most often with patients who have heart conditions, which are common complications of diabetes.