The agonist muscle is the main muscle that creates movement at a joint.
The agonist muscle is also called the “primary mover.” During tummy time, a baby pushes up from the floor with their arms and extends their elbows. In this case the, elbow extenders or triceps brachii are the agonists!
![A baby in a red sweater pushes up with straight arms in tummy time. A label for the agonist muscle points to the back of the upper arm.](https://mykidsplace.zone/wp-content/uploads/2021/03/Agonist-Muscle-Example-1024x1024.png)