Muscle Lengths in Elbow Extension

Steps:

• Identify biceps as elbow flexor: it lengthens maximally when elbow is extended.
• Identify triceps as elbow extensor: it shortens minimally in full extension.
• Expect graph with biceps at peak length and triceps at trough length for straight arm.
• Match to option showing this inverse relationship at 180° elbow angle.

Why C is correct:

• C illustrates biceps at maximum extension length and triceps at minimum, aligning with anatomical lever mechanics where flexors stretch and extensors relax in full arm straightening.

Why the others are wrong:

• A shows both muscles shortened, incorrect for extension.
• B depicts biceps shortened, which occurs in flexion, not extension.
• D illustrates triceps lengthened, opposite of its role in extension.

Final answer: C