Hyperextensions are a type of exercise that works the muscles of the lower back, glutes, and hamstrings. If you are looking for synonyms for the word "hyperextensions," you might consider terms like "back extensions," "Romanian deadlifts," or "good mornings." These exercises are all similar in that they target the same muscle groups as hyperextensions and are often included in strength training and bodybuilding routines. While the specific movements may differ slightly, all of these exercises focus on strengthening the posterior chain (backside of the body) and can help improve posture, reduce back pain, and increase athletic performance.