which muscle would be a prime mover of knee extension?
SHARE SHARE TWEET EMAIL. To get the workout results you want, you need to know which muscle is acting as the agonist during an exercise. An agonistic muscle -- also called a prime mover -- is the main muscle used to perform a certain movement. A left-leg extension is a movement that uses the quadriceps -- the front thigh muscle -- as the agonist. You can do a left-leg extension, which is a single-joint movement, with anything that provides resistance.