Which type of mover is MOST powerful during the contraction?

An agonist mover is most powerful during contraction.

Explanation:

An agonist muscle is the main working or the prime mover. It is the muscle that undergoes strain, shortens and contracts. Antagonist muscles aid in relaxation.

Agonistic prime movers are the main muscles that facilitate movement. along with synergist muscles, agonists primarily involves in muscle contraction. this also initiates joint range of motion by contracting. These muscles especially aid in concentric contraction where shortening takes place.

For example, during a biceps curl, the biceps muscle acts agonistic, shortens and aids in contraction; whereas the triceps lengthens and aids in relaxation.