During elbow extension, which statement best describes the relationship of the biceps and triceps?

• A. Both Biceps And Triceps Contract
• B. Biceps Contracts While Triceps Relaxed
• C. Triceps Contracts While Biceps Relaxed
• D. Neither Contracts

Answer: (C)

Elbow extension is produced by the opposing actions of an elbow extensor and its antagonist. The triceps brachii is the primary muscle that shortens to straighten the arm, pulling the forearm into extension. At the same time, the biceps brachii, a flexor, should relax or be passively lengthened so it does not oppose the movement. If the biceps were actively contracting, it would flex the elbow and oppose the triceps, hindering or blocking extension. In normal, controlled extension, you mainly see the triceps contracting while the biceps relaxes. (Some co-contraction can occur for stabilization, but the typical description for extending the elbow is the triceps contracting with the biceps relaxed.)