A shoulder flexion apparatus tones and strengthens the shoulder muscles, including the anterior deltoid muscles. The apparatus may provide a resistance having a downward force vector. The resistance may be applied to a user via a cable guided by one or more pulleys to the user. In one or more embodiments, a guide assembly may be provided to quickly and easily reposition the cable and the force vector of the resistance that the cable provides. The guide assembly thus allows rapid switching between shoulder exercises to tone and strengthen the shoulder muscles. The apparatus may comprise one or more sections corresponding to the left and right side of the user's body. In this manner, the sections may independently provide resistance to each of the user's shoulders.