For centuries, treadmills in the form of treadwheels have been used for punishment or to generate power for grinding grain or pump water. The forerunner of today’s treadmill for exercise and medical therapy was invented in 1952 at the University of Washington to diagnose heart disease.
A treadmill is basically a conveyor belt stretched between 2 rollers with a firm surface underneath the upper layer of the belt with the supporting surface cushioned to reduce the impact of walking or running. Very cheap treadmills are often not powered, as you walk with the deck at an incline, it moves underneath you.
Typically though, on a modern exercise treadmill, the treadmill belt is moving with the help of a motor attached to one of the rollers. The speed of the treadmill belt can be adjusted, with 12 MPH the fastest setting found, while the incline of the running deck can be as steep as 15pct on some treadmills.
Treadmills offer both advantages and disadvantages. Weather is no longer an issue and the cushioned running deck is easier on the joints. Also, with a variety of programs, training can be accurately controlled.
Conversely, without wind resistance, it easier to run on a treadmill by as much as 5pct and some runners develop poor running mechanics.