A rowing machine is a piece of cardio equipment that simulates rowing a boat. It works the back and leg muscles in unison. Crossfit implements this tool in many of its workouts. You can find this machine in most big public gyms and Crossfit gyms. Unlike other cardio equipment, the rowing machine is extremely light. It also has wheels on the front and the ability to stand upright for storage. It is very easy to pick one end up and roll it around and store in the upright position. This would be a perfect cardio tool for a home gym.