Blonde Girl Taking Pictures On The Treadmill

A treadmill is an exercise machine for running or walking while staying in one place. The word treadmill traditionally refers to a type of mill which was operated by a person or animal treading steps of a wheel to grind grain (treadwheel)
The machine provides a moving platform with a wide conveyor belt and an electric motor or a flywheel. The belt moves to the rear allowing a person to walk or run an equal, and necessarily opposite, velocity. The rate at which the belt moves is the rate of walking or running. Thus, the speed of running may be controlled and measured. The more expensive, heavy-duty versions are motor-driven (usually by an electric motor). The simpler, lighter, and less expensive versions passively resist the motion, moving only when the walker pushes the belt with their feet. The latter are known as "manual treadmills".