Flexion of the elbow while holding a toothbrush uses which muscle as the primary mover?

Flexion of the elbow while holding a toothbrush uses which muscle as the primary mover?

• A. Brachioradialis
• B. Brachialis
• C. Biceps brachii
• D. Pronator teres

Answer: (B)

The muscle that does most of the work when you bend the elbow while gripping a toothbrush is the brachialis. This muscle sits deep to the biceps and attaches directly to the ulna, so it acts to flex the elbow with a strong, reliable pull regardless of how the forearm is rotated. When you brush your teeth, your forearm is typically pronated (palm facing down), which reduces the advantage of the biceps brachii (the primary elbow flexor when the forearm is supinated). The brachioradialis works best when the forearm is in a neutral position, so it isn’t the main driver in this pronated position. Pronator teres mainly pronates the forearm and only assists with elbow flexion, not as the primary mover.

The muscle that does most of the work when you bend the elbow while gripping a toothbrush is the brachialis. This muscle sits deep to the biceps and attaches directly to the ulna, so it acts to flex the elbow with a strong, reliable pull regardless of how the forearm is rotated. When you brush your teeth, your forearm is typically pronated (palm facing down), which reduces the advantage of the biceps brachii (the primary elbow flexor when the forearm is supinated). The brachioradialis works best when the forearm is in a neutral position, so it isn’t the main driver in this pronated position. Pronator teres mainly pronates the forearm and only assists with elbow flexion, not as the primary mover.