Question

select the correct answer.
how do your arm muscles work to lift a mug of coffee to your lips?

a. the biceps muscle contracts while the triceps muscle relaxes. only then can the forearm move up to lift the mug.

b. the muscle tendons in your arms stretch to their limit as a result of the flexibility exercises that lift the mug.

c. your muscles rapidly increase the speed at which they twitch to trigger your arm movement.

d. your biceps and triceps muscles first relax, and then the arm muscle raises the mug.

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Explanation:

To lift the mug, the biceps (flexor) contracts to bend the arm, while the triceps (extensor) relaxes. Option B is wrong as tendons don't stretch to lift; C is wrong as muscle twitch speed isn't the mechanism; D is wrong as muscles don't both relax first. Only A correctly describes the antagonistic muscle action.

Answer:

A. The biceps muscle contracts while the triceps muscle relaxes. Only then can the forearm move up to lift the mug.