A pull up itself is what is known as a compound exercise which means it physically engages lots of different muscle groups by the action of carrying it out. You are going to challenge and use smaller supportive as well as larger muscle groups including your latissimus dorsi (commonly referred to as lats) as well as your biceps. The large multi-joint moves that you can carry out on a pull up bar mean you are using and stabilising many muscles from a simple series of exercises. If your Pull Up bar additionally converts to allow you to do Triceps Dips and Hanging Leg Raises, you can literally work your entire upper body, arms and core with a Pull Up bar.\r