What defines isometric contraction?

Isometric contraction is characterized by a static contraction where there is no change in joint angle, meaning that the muscle is activated and generating tension, but the overall length of the muscle remains the same. This type of contraction occurs when force is applied against an immovable object, or when a muscle stabilizes a joint without movement, maintaining posture or holding a position.

In activities such as pushing against a wall or holding a weight in a fixed position, the muscle maintains its length despite the force being exerted, leading to stability without actual motion. This distinguishes isometric contractions from other types, which involve changes in muscle length either through shortening or lengthening.