Glossary · Biomechanics
Metabolic cost
Also called metabolic energy, energy cost, energy expenditure, muscle energy
The chemical energy muscles burn to make force and movement. It is what makes a human tired, and what a motor's electricity bill doesn't capture.
A muscle burns energy (from ATP) whenever it is excited, not only when it does work: holding a weight still, or two muscles pulling against each other in co-contraction, costs energy and moves nothing. The cost rises with how strongly a muscle is activated, how much of it is used, and how fast it shortens; doing work on the body adds more. Models of it, built from experiments on real muscle, let a simulation estimate how much energy a movement would take and how tiring it would be.
This is part of why people move the way they do. Walking speed, the length of a step, and a fighter’s relaxed guard between punches all keep energy use down, and a fighter who wastes energy tires before the last round.
In this project
Muscles instead of motors did not measure metabolic cost yet. The muscle bodies give the numbers it needs (every muscle’s activation, length and speed), so it can be added later.