How your body makes energy

Three engines

Your body makes energy in three ways. Think of three engines. All three are always running. What changes is which one does most of the work.

The sprint engine

Up to about ten seconds. A heavy lift, a jump, a dash for the bus. It runs low fast and mostly refills in two to three minutes. That is why you rest between heavy sets.

The hard-minute engine

Ten seconds to about a minute. A fast set of 15, a run up a hill. It is quick, and it burns.

The all-day engine

A minute and beyond. Walks, long rides, and the recovery in between. It is slow to get going and almost never runs out.

How to train all three

Lift a few times a week. Move easily most days. Add one hard session when you feel ready. That covers all three.