During contraction when the length of muscle increases it is called:

Question

Accepted Answer

The correct option is (1):
Eccentric contraction is the correct answer. This type of muscle action occurs when the tension generated by the muscle is insufficient to overcome the external load, causing the muscle fibers to actively lengthen while contracting. In simpler terms, the muscle is resisting a force greater than its own, effectively acting as a "brake" to control the movement. A classic example is the controlled lowering of a weight during a bicep curl or the descent phase of a squat. Eccentric movements are crucially important as they allow muscles to handle higher loads, which is highly beneficial for strength gains, muscle hypertrophy, and enhancing tendon resilience for injury prevention.

The incorrect option is (2):
Concentric contraction is incorrect because it describes the muscle *shortening* while producing tension. In this scenario, the force generated by the muscle is greater than the external resistance, causing the joint angle to change and the body part to accelerate or lift. It is the direct opposite of the condition described in the question, where the muscle length is increasing. Concentric contractions are primarily associated with the power and speed aspects of a movement.

The incorrect option is (3):
Auxo-tonic contraction is a term used for a dynamic contraction where *both* the tension (force) and the length of the muscle are changing simultaneously. While an eccentric contraction technically falls under this broader category, the term 'Eccentric contraction' is the precise and universally accepted anatomical term for the specific action where a muscle is lengthening *while* under tension. Therefore, 'Auxo-tonic' is too general and is not the best fit for this fundamental definition.

The incorrect option is (4):
Static-Muscle contraction is another name for an Isometric contraction, which means 'equal measure' or 'equal length'. In an isometric contraction, the muscle produces tension but its total length does *not* change. This occurs when the force the muscle generates exactly matches the external load, such as holding a weight steady in mid-air or pushing against a fixed, immovable object. As the muscle's length remains constant, this option clearly contradicts the question's premise that the muscle length *increases*.