Question

In isometric contraction:
A. Tone changed but length same
B. Length changed but tone same
C. Length and tone both same
D. Length and tone both change

Answer 1

Hint: “Isometric” is a combination of two greek words, “isos” and “metria”. Isos means equal whereas metria is the extent. This type of contraction is also referred to as static contraction in which tension develops in muscles.

Complete answer:
Isometric contraction refers to contraction of muscles when both its ends are fixed by tendons. In this condition, the length of muscle remains the same but its tone increases. Examples include pushing your arm or hand against a rigid surface. The muscle will feel tension without any length change.
Other options which claim that in isometric muscle contraction, length and tone both remain same or length changed but tone same or length and tone both change are incorrect as all contractions involve either change in length or tone of a muscle.
Reduction in length of muscles without altering its tone occurs in case of isotonic muscle contractions which are the simplest type of contractions. During this, muscles contract without any attachment. Examples of isotonic contraction includes, bicep curls, squats, push-ups, stair climbing etc. whereas both length of muscle and tone changes in auxotonic contraction which includes almost all muscle contractions happening in day to day life.

So, the correct answer is option “A” that is in isometric contraction, tone changed but length remains the same.

Note: Muscle length refers to the change in length of a muscle whereas tone refers to the resistance of muscles against elongation or stretch. During muscle contraction, change in muscle length or tone occurs as a response to certain stimuli.