As one muscle contracts the must relax.?

As one muscle contracts, its antagonistic muscle must relax for smooth and efficient movement.

When a muscle contracts, it generates tension and shortens, thereby moving a body part in a specific direction. For this movement to occur effectively, the opposing muscle (the antagonist) needs to relax and lengthen simultaneously. This coordinated action between opposing muscle groups allows for controlled and balanced movements.

For example, during bicep curls, the bicep (flexor) muscle contracts to bend the elbow joint, while the tricep (extensor) muscle relaxes to allow the elbow to flex. If the tricep did not relax, it would resist the bicep's contraction, making it difficult or impossible to complete the bicep curl.

This reciprocal relationship between opposing muscles not only allows for dynamic movements but also helps maintain postural stability and prevents muscle imbalances or strains.