What type of muscle action generates tension in the muscle without lengthening or shortening it?

The type of muscle action that generates tension without lengthening or shortening the muscle is known as isometric or static muscle action. In an isometric contraction, the muscle exerts force against an immovable object or maintains a position against resistance without changing its length. This is commonly seen in exercises where you hold a position, such as a plank or wall sit, where muscle fibers are activated, but there is no visible movement of the joint.

Concentric actions involve muscle shortening to produce movement, while eccentric actions occur when muscles lengthen under tension, typically during the lowering phase of a movement. Plyometric actions combine strength and speed, involving dynamic muscle contractions in rapid succession. Thus, isometric actions are unique in that they focus solely on maintaining tension without any change in muscle length or joint angle.