What is the definition of an isometric contraction?

An isometric contraction is defined as a contraction in which muscle fibers generate force without a change in muscle length. This means that the muscle is engaged and working hard, but it does not shorten or lengthen during the contraction.

Isometric contractions are often seen in activities where an individual holds a position against resistance, such as maintaining a plank position or holding a wall sit. These types of contractions are beneficial for building strength and stability without the movement associated with dynamic contractions where the muscle length changes.

The other definitions do not accurately capture the essence of isometric contractions. For example, a contraction that results in muscle lengthening corresponds to an eccentric contraction, which involves muscle fibers extending while under tension. A contraction characterized by rapid movement could refer to isotonic contractions, where muscles change length to produce movement. Similarly, a contraction that causes joint rotation would typically involve dynamic muscle contractions, either concentric or eccentric. Thus, the definition that most accurately describes an isometric contraction is one where there is no change in muscle length while tension is maintained.