And motor units can basically work together to carry out a motion in a coordinated and smooth fashion. So many different motor units can work together to create smooth and coordinated motion. If a certain activity requires a small force, a small number of motor units are actually used. On the other hand, if the activity requires a relatively large force when for example, we're lifting some type of heavy object, many motor neurons are actually used. Now, typically small muscles like the muscles found in our fingers require few motor units while large muscles like the muscles in our legs require a larger number of motor units. So let's take a look at the following diagram to see what we mean by a motor unit.