ACSM
010-111 · Question #13
010-111 Question #13: Real Exam Question with Answer & Explanation
The correct answer is B. Isotonic eccentric. When a constant external load causes a muscle to lengthen despite maximal effort, the contraction is classified as isotonic eccentric. The barbell weight remains unchanged (isotonic) while the elbow flexors lengthen as the joint moves into extension (eccentric).
Question
A subject with elbows held at 90 degrees of flexion is handed a 150 lb (68.1kg) barbell. Even though he exerts maximal tension, the barbell causes the joint angle to increase to 170 degrees. Which one of the following describes the muscle action during the extension?
Options
- AIsotonic concentric
- BIsotonic eccentric
- CIsokinetic concentric
- DIsokinetic eccentric
Explanation
When a constant external load causes a muscle to lengthen despite maximal effort, the contraction is classified as isotonic eccentric. The barbell weight remains unchanged (isotonic) while the elbow flexors lengthen as the joint moves into extension (eccentric).
Common mistakes.
- A. Concentric contraction requires the muscle to shorten and the joint angle to decrease toward flexion, the opposite of what is described.
- C. Isokinetic contractions require a constant velocity maintained by a specialized dynamometer; a free barbell cannot produce isokinetic conditions.
- D. Isokinetic classification requires constant-velocity equipment regardless of contraction direction; it cannot occur with free weights.
Concept tested. Isotonic eccentric muscle contraction identification
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