The medial head is one of the three heads which comprise the triceps brachii, the muscle which is located to the rear of the upper arm. As shown on the muscle diagram, the medial head is located to the inner region of the arm.
The triceps are effectively targeted with exercises which involve the extension of the arm. As such, they can be isolated with the likes of skull crushers, French press and triceps pushdowns. Multi-joint alternatives include the close grip bench press, bench dips and triceps dips.