A
treadmill is a device generally for walking or running while staying in the same place. Treadmills were introduced before the development of powered
machines, to harness the power of animals or humans to do work, often a type of
mill that was operated by a person or animal treading steps of a
treadwheel to grind grain. In later times, treadmills were used as punishment devices for people sentenced to hard labour in prisons. The terms
treadmill and
treadwheel were used interchangeably for the power and punishment mechanisms.