Final answer:
The brachioradialis muscle is primarily located in the forearm and works to flex the forearm, unlike the biceps brachii which resides in the arm.
Step-by-step explanation:
The muscle belly of the brachioradialis lies primarily in the forearm, unlike the biceps brachii which is located in the arm. The brachioradialis is capable of flexing the forearm quickly and can also help lift a load slowly. It is worth noting that the brachioradialis, along with the biceps brachii and brachialis, are all involved in the flexion of the forearm.
While the biceps brachii crosses both the shoulder and elbow joints, contributing to flexion and supination of the forearm as well as flexing the arm at the shoulder, the brachialis is located deep to the biceps brachii and adds power to forearm flexion. In contrast, the brachioradialis is part of the muscles that form the anterior compartment of the arm, specifically influencing the movement of the forearm.