Question

The muscular contraction in which the tension remains the same and the mechanical work is also done is called
A) Isotonic contraction
B) Tetanus
C) Isometric contraction
D) Single muscle twitch

Answer 1

Hint: As we know muscle contraction is the process of activation of tension-generating sites within the muscle fibers. Muscle contraction does not necessarily mean muscle shortening because muscle tension can be generated without the changes in muscle length. The termination of muscle contraction is followed by muscle relaxation, which is basically a return of the muscle fibers to their low tension-generating state.

Complete answer:
Isotonic contractions maintain a constant tension in the muscle as the muscle changes its length. This phenomenon can occur only when a muscle's maximal force of contraction exceeds the total load on the muscle. Isotonic muscle contractions can be either concentric in which the muscle shortens or can be eccentric where the muscle lengthens.
A tetanic contraction is a sustained muscle contraction which is produced when the motor nerve that innervates a skeletal muscle emits an action potentials at a very high rate
In isometric contraction instead of allowing the muscle to lengthen or shorten, it is held at a constant length. In this case the weight of the object would be pulling downward, but hands and arms would be opposing this motion with equal force going upwards.
A fasciculation which is also called as a muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, which involves the fine muscle fibers.

Therefore we can say that the correct answer is option A) which is Isotonic contraction.

Note:
Muscle contractions can be described based on the two variables which are length and tension. If the muscle length shortens then the contraction is concentric whereas if the muscle length lengthens then the contraction is eccentric. Therefore, we can say that neither length nor the tension is likely to remain the same in muscles that contract during the locomotor activity.