Treadmill

A treadmill is a device for walking or running, while staying in the same place. Before there was steam power, such treadmills were used to power machines. That way, the work of animals or people could be used in the machines. Such treadmills were also used as a form of punishment in prisons.

A horse grinds olives in a treadmill in the Atlas Mountains

Donkey-powered grinding mill, in Oxaca, Mexico

Sportspeople are being tested on a treadmill