A treadmills is stationary equipment that allows you to walk, run, or climb. Treadmills were created before powered devices were established to harness the power of animals or people to do tasks. Treadmills are a type of mill in which grain is ground by a person or animal pacing the treadwheel's steps. Treadmills were later used in prisons as a form of punishment for people sentenced to hard labor. Treadmill and treadwheel were equivalent terms for power and punishment devices.