Antagonist muscles are pairs of muscles that work against each other to create movement. When one muscle contracts, the other relaxes, allowing for smooth and controlled motion. For example, during a bicep curl, the biceps contract to lift the weight, while the triceps act as the antagonist, relaxing to enable the movement. This relationship is essential for maintaining balance and stability in the body. Antagonist muscles help prevent injuries by ensuring that movements are coordinated and controlled. Proper functioning of these muscle pairs is crucial for activities ranging from simple tasks to complex athletic performances.