Biceps Exercise Guides – Photos and Instructions for Big Arms What people commonly refer to as the biceps are actually two distinct muscles: the biceps brachii and the brachialis. Both muscles run along the front of the upper arm, from the shoulder to the elbow. The biceps brachii is responsible for the ball-like “head” on your biceps; the brachalis is the larger of the two, located underneath the biceps brachii. Both muscles that make up the biceps help flex your elbow. In addition, the biceps brachii helps to supinate your forearm. This is very helpful in swinging a racquet in sports like racquetball and tennis.