What must we do if we want flexion?

• A. Inhibit or Turn Off the Antagonist
• B. Stimulate the Antagonist
• C. Strengthen the Agonist
• D. Contract Both Antagonist and Agonist

Answer: (A)

Flexion is produced when the muscles that bend a joint (the flexors) contract while the muscles that straighten it (the extensors) are quiet or inhibited. The crucial step is removing the opposing force from the antagonist so the flexor can shorten the joint angle without resistance. That’s why inhibiting the antagonist is the best action: it clears the way for the flexor to create the movement.

If you stimulated the antagonist, you’d promote the opposite movement (extension) rather than flexion. Strengthening the agonist helps, but without reducing the antagonist’s activity, flexion can be limited by opposing tension. Contracting both sides at once would cancel the movement. In nervous system terms, reciprocal inhibition coordinates this by activating the flexor while dampening the extensor to achieve smooth flexion.