MariposasMET (Metabolic Equivalent)
MET, short for Metabolic Equivalent of Task, is a way of expressing how hard your body is working relative to doing nothing. One MET is defined as the energy your body uses just sitting quietly, and every activity gets assigned a multiple of that baseline. Running at a moderate pace might carry a MET of 8 or 9, meaning your body is burning roughly 8 or 9 times as much energy as it would at rest. The number lets coaches, researchers, and fitness trackers compare very different activities on the same scale, so you can meaningfully stack cycling against swimming against a brisk walk. The nuance most people miss is that published MET values are population averages based on a reference body weight, so a heavier or lighter person will have a different actual calorie burn even if they're doing the same activity at the same MET. It's a useful approximation, not a precise personal readout.
Example
A person sits at a desk with a MET of roughly 1.3, then goes for a vigorous hike carrying a pack, which might score around a MET of 7. That single number tells you the hike demands about five times more metabolic effort than sitting, without needing a lab test or heart rate monitor. Fitness apps use this kind of MET lookup table constantly to estimate calorie totals from workout duration and body weight.