Not a lot of people like the treadmill. Sure, there are runners who love running, but you’d be hard-pressed to find one who actually prefers the monotonous pounding of a treadmill to running outside on a trail or track. If you’ve ever found yourself wondering why on earth you’re going through the torture of running in place, it’s no coincidence — the treadmill’s original purpose was to be cruel and unusual punishment.

Back in the 1800s, the forerunner to the treadmill was invented so prison inmates could make themselves useful by turning a large paddlewheel by stepping on its spokes. The wheel would in turn pump out water, crush grain, or power a mill: the source of the name “treadmill.” Prisoners were often forced to spend up to six hours a day on the wheel, which was the equivalent of climbing about 5,000 to 14,000 feet.

The machines were eventually banned for being excessively cruel, but they made a comeback in the mid-20th century. Once the jogging craze hit the U.S. in the 1970s, treadmills became a very familiar part of the health and fitness landscape we know today. Check out the video to watch the evolution of the treadmill from torture device to… well, marketed torture device. Kidding. Sort of.