by Cassie Arnold

Exercising on a treadmill often feels like torture, and that’s not exactly a coincidence.

In 1818, an English civil engineer named Sir William Cubitt devised a machine called the “tread-wheel” to reform stubborn and idle convicts.

Prisoners would step on the 24 spokes of a large paddle wheel, climbing it like a modern StairMaster. As the spokes turned, the gears were used to pump water or crush grain. (Hence the eventual name treadmill.) In grueling eight-hour shifts, prisoners would climb the equivalent of 7,200 feet. The exertion, combined with poor diets, often led to injury and illness (as well as rock-hard glutes), but that didn’t stop penitentiaries all over Britain and the United States from buying the machines. In 1824, prison guard James Hardie credited the device with taming New York’s more defiant inmates. He wrote that it was the treadmill’s “monotonous steadiness, and not its severity, which constitutes its terror."

Over the years, American wardens gradually stopped using the treadmill in favor of other backbreaking tasks, such as picking cotton, breaking rocks, or laying bricks. In England, the treadmill persisted until the late 19th century, when it was abandoned for being too cruel. The machine was all but lost to history. But when Dr. Kenneth Cooper demonstrated the health benefits of aerobic exercise in the 1960s, the treadmill made a triumphant return. Today, well-paid personal trainers have happily taken the place of prison wardens.