Question

9. Which of the following statements is true for an eccentric muscular contraction.

1. The muscle lengthens.

2. The maximum possible tension generated by a muscle at a given joint position is

   smaller during an eccentric contraction when compared to an isometric contraction.

3. Shortening of m. triceps during elbow extension is an example of an eccentric

   contraction.

4. Requires an external force acting on the bone to which the muscle is attached.

Answer 1

Question 9.

Which of the following statements is true for an eccentric muscular contraction?

Answer: The muscle lengthens.

Explanation: During eccentric muscular contraction, the muscle length increases i.e. the muscle lengthens. Examples of this is the downward phase of biceps curls exercise during which the length of the biceps brachii muscle increases. This lengthening of the biceps brachii muscle slows down the extension of the elbow joint.

Muscular contraction are broadly of two types namely isotonic contraction and isometric contraction. In isotonic contraction, the tension in the muscle remains the same but the length of the muscle changes.

Isotonic contraction is further of two types namely concentric contraction and eccentric contraction. In isotonic concentric contraction, the tension in the muscle remains the same but the length of the muscle decreases. Example of isotonic concentric contraction is the upward phase of biceps curls exercise during which the length of the biceps brachii muscle decreases and the muscle becomes shortened. This pulls the forearm in the upward direction and causes flexion at the elbow joint. In isotonic eccentric contraction, the tension in the muscle remains the same but the length of the muscle increases. Example of isotonic eccentric muscular contraction is the downward phase of biceps curls exercise during which the length of the biceps brachii muscle increases which slows down the extension of the elbow and pulls the forearm in the downward direction.

Isometric contraction is the type of muscular contraction in which the contraction of the muscle but no change in the length of the muscle. Example of isometric contraction is the contraction of biceps brachii during biceps curls exercise when the individual is simply holding the weight still. There is tension in the biceps brachii muscle due to the weight of the dumbbells but there is no change in the length of the muscle. As there is no change in the length of the muscle, there is no flexion or extension of the elbow.

During eccentric contraction the tension remains the same(as it is an isotonic contraction) but the length of the muscle increases whereas during isotonic contraction tension increases in the muscle but the length of the muscle remains the same. Thus, the maximum possible tension generated by a muscle at a given joint is smaller during an eccentric contraction as compared to isometric contraction.

Shortening of muscle triceps during elbow extension is an example of eccentric contraction is an incorrect statement as during eccentric contraction the muscle length increases and the muscle lengthens. Shortening of the muscle occurs during concentric contraction.