Question

Skeletal muscles are recruited to lift loads. If the force generated in the muscle due to contraction is not sufficient to lift the load, it is known as _________ contraction.

• A. Isometric
• B. Isotonic
• C. Isokinetic
• D. Isoinertial

Hint:

When a muscle contracts but cannot lift a load, the length stays fixed. This “fixed length under tension” condition is the defining feature of isometric contraction.

Answer 1

The Correct Option is A

To determine the correct contraction type, we must analyze how muscles behave under varying loads. When a muscle contracts, it can either change its length or remain the same length, depending on the external force. If the muscle produces enough force to lift or move a load, it undergoes \emph{isotonic contraction}, where the muscle length changes while the tension remains relatively constant. However, when the load is too heavy, the muscle still attempts to contract and generate force, but the force is not enough to overcome gravity or resistance. In such a case, the muscle \emph{does not change its length}, even though it is actively contracting. This type of contraction is known as \emph{isometric contraction}. A common example is pushing against an immovable object or holding a heavy weight that you cannot lift—your muscles produce tension, but no movement occurs. Options like \emph{isokinetic contraction} refer to contractions performed at constant velocity using specialized equipment, and \emph{isoinertial contraction} involves constant resistance. Neither of these describes the inability to lift a load. Therefore, the correct and most appropriate term for the scenario where force is generated but insufficient to produce movement is \emph{isometric contraction}. Thus, the correct answer is (A) Isometric.