Meaningless METS: studying the link between physical activity and health

Physical activity is good for health. Few would oppose this contention. But, curiously, we do not definitively know how much the type (occupational, recreational, daily living) and quantity of physical activity reduces the risk of common conditions. This imprecision stems essentially from the myriad different ways physical activity has been appraised in epidemiological studies. Some studies investigated physical activity as a whole, while others concentrated on specific types of activity. Different metrics have been used for quantification from just dummy categories (such as high versus low) to quintiles of hours a week. The metabolic equivalent of tasks (MET) is a standardised metric that expresses the energy spent during a specific activity. The MET is defined as the ratio of the metabolic rate during that activity to the metabolic rate when resting.1 A classification system was developed in 19932 and updated …