Which type of muscle works in opposition to another muscle?

The type of muscle that works in opposition to another muscle is known as the antagonist. Antagonist muscles act to counteract the action of the agonist muscle, which is the muscle primarily responsible for producing a specific movement. When one muscle contracts to create movement, the antagonist relaxes or lengthens to allow that movement to occur.

For instance, during a bicep curl, the biceps brachii is the agonist that contracts to lift the forearm. At the same time, the triceps muscle acts as the antagonist, relaxing to allow for this movement. This coordinated action is crucial in maintaining control and balance in movements, enabling smooth and effective motion while preventing injury.