How MET tables work
One MET is the rate of energy expenditure at rest — about 1 kcal per kg of body weight per hour. A 4-MET activity therefore costs four times that. The Compendium of Physical Activities is the most widely cited public-health reference for activity-level METs, originally published in 1993 and updated in 2000 and 2011.
Road, mountain, or trainer?
Road cycling METs scale with speed because air drag rises with the cube of velocity — so a 25 km/h road ride is much harder than 16 km/h. Mountain biking has a single 8.5-MET value because terrain and technical features dominate over speed. Stationary trainers split into “light” and “vigorous” because cadence and resistance vary so much.
Why your power meter beats this calculator
A direct-drive power meter measures the actual mechanical work you put into the pedals and converts it to kcal at ~22% gross efficiency. That’s accurate to ~±2%. MET tables are population averages — the right tool for public-health planning, the wrong tool for tracking your specific weekly training load. If you have a power meter, trust it.