Question

17.when muscles work in pairs, the ____________ causes the primary movement, and the ____________ works against this movement.

Explanation:

In muscle pairs, the agonist (prime mover) contracts to cause the primary movement. The antagonist muscle relaxes initially but can also contract to oppose the movement (e.g., when extending the elbow, the triceps (agonist) contracts, and the biceps (antagonist) can oppose if needed).

Answer:

agonist; antagonist