The brachialis is the muscle which runs beneath the biceps, and like its more famous next door neighbour, is responsible for the flexion of the arm (although to a lesser degree).

The arm flexor muscles are typically trained in two ways. Firstly, they receive sufficient engagement during many rowing and pull up exercises which require the arms to flex, although these are widely seen as merely back exercises. Secondly, various arm curling exercises are effective choices for isolating the arm flexors.