The piece of gym equipment with a moving belt that lets you walk or run while staying in place is a treadmill. Its belt travels beneath the user, usually toward the rear, while the deck remains fixed, creating the sensation of moving forward without changing location.
Modern treadmills are commonly powered by an electric motor, although manual models move when the user pushes the belt with their feet. Speed can be selected and measured precisely, making treadmills useful for exercise, running practice, rehabilitation, and controlled fitness testing. Medical versions can be connected to equipment that monitors heart rhythm, blood pressure, or oxygen use.
The word treadmill originally referred to treadwheels powered by people or animals to perform work, such as grinding grain. In the 19th century, treadmills were also used as prison hard-labor devices. The exercise-machine version emerged much later: a clinical treadmill for heart and lung testing was developed at the University of Washington in 1952, while home models became more practical in the late 1960s.