Muscle physiology: force-velocity relation: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Muscle physiology: force-velocity relation

Sample item

In an isolated skeletal muscle lifting different loads, shortening velocity falls as the load increases. At what load is mechanical power output (force x velocity) greatest?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. About one third of the maximum isometric force

Power is the product of force and velocity. At zero load velocity is maximal but force is nil; at maximal isometric load force is greatest but velocity is zero. Power is therefore zero at both extremes and peaks at an intermediate load of roughly 30 to 40 percent of maximum force.

Option by option

  • A. Zero load, where velocity is maximal

    At zero load no force is produced, so power is zero.

  • B. The maximum isometric load, where force is greatest

    At maximum isometric load there is no shortening, so no external work is done and power is zero.

  • C. About one third of the maximum isometric force (correct)

    Correct. Intermediate loads give the largest force-velocity product.

  • D. About 90 percent of the maximum isometric force

    At 90 percent of maximum force velocity is very low, so power is again low.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, About one third of the maximum isometric force. Power is the product of force and velocity.

Why is "Zero load, where velocity is maximal" not the answer?

At zero load no force is produced, so power is zero.

Why is "The maximum isometric load, where force is greatest" not the answer?

At maximum isometric load there is no shortening, so no external work is done and power is zero.

Why is "About 90 percent of the maximum isometric force" not the answer?

At 90 percent of maximum force velocity is very low, so power is again low.

What concept does this question test?

It tests Muscle physiology: force-velocity relation in Physiology. At zero load velocity is maximal but force is nil; at maximal isometric load force is greatest but velocity is zero. Power is therefore zero at both extremes and peaks at an intermediate load of roughly 30 to 40 percent of maximum force.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Muscle physiology: force-velocity relation?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.