When the extensor digitorum contracts, which action occurs?

The extensor digitorum is a muscle located in the posterior compartment of the forearm, primarily responsible for extending the fingers (digits) at the metacarpophalangeal joints and to some extent at the interphalangeal joints. When this muscle contracts, it results in digit extension, which is the primary action associated with it.

In addition, while the extensor digitorum primarily targets the fingers, its contraction can also assist in extending the wrist, though this action is typically a secondary effect rather than the muscle's primary function. The muscle works alongside other extensors of the wrist to facilitate this extension, which is why both digit extension and wrist extension can occur simultaneously during its contraction.

Elbow extension is not a direct action of the extensor digitorum; however, because the movement of the forearm and fingers may influence the overall positioning during activities, it can assist in this action through the kinetic chain. Therefore, when considering the contributions of the extensor digitorum—particularly its primary role in digit extension alongside the potential for secondary effects on wrist and elbow extension—it is accurate to conclude that the contraction of extensor digitorum results in both digit and wrist extension, hence the inclusion of both actions is justified