When the arm is bent at the elbow, the biceps contracts while the triceps
- A. contracts at the same time
- B. contracts even more strongly
- C. relaxes
- D. detaches from the bone
Explanation
Muscles can only pull, so the flexor biceps and the extensor triceps work as antagonists: one contracts while the other relaxes, and they swap roles when the arm is straightened. Both contracting together would lock the joint.
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