Muscle · Upper arm

Brachioradialis

Musculus brachioradialis

The long muscle that forms the fleshy ridge on the thumb side of the forearm. It is an elbow flexor that is oddly filed with the extensors — it sits in the back compartment and is supplied by the radial nerve, but it pulls the forearm forward rather than back. It is at its strongest with the thumb pointing up, the neutral hammer-holding position, which is exactly the grip used for carrying a bag or swinging a tool, so it takes a heavy share of everyday load.