The rhomboideus is a muscle located in the upper back that helps to retract and stabilize the shoulder blade. Synonyms for this muscle include rhomboid, rhomboid minor, and rhomboid major. The rhomboid minor is the smaller portion of the muscle while the rhomboid major is the larger portion. Other muscles that work in conjunction with the rhomboideus include the trapezius and serratus anterior. Strengthening exercises for the rhomboideus can improve posture and help to prevent shoulder injuries. Popular exercises include rowing, scapular retractions, and reverse flys. It is important to properly warm up before performing any exercises to avoid injury.