The constant thud underneath your feet, the constrained space, and the monotony of going nowhere fast. It feels like hours have gone by, but it's only been eleven minutes, and you wonder, "Why am I torturing myself? This thing has got to be considered  a cruel and unusual punishment." Actually, that's exactly  what it is, or was. You see, in the 1800s, treadmills were created  to punish English prisoners. At the time, the English prison system was abysmally bad. Execution and deportation were often the punishments of choice, and those who were locked away faced hours of solitude in filthy cells. So social movements led by religious groups, philanthropies, and celebrities, like Charles Dickens, sought to change these dire conditions and help reform the prisoners. When their movement succeeded, entire prisons were remodeled and new forms of rehabilitation, such as the treadmill, were introduced. Here's how the original version, invented in 1818 by English engineer  Sir William Cubitt, worked. Prisoners stepped on 24 spokes of a large paddle wheel. As the wheel turned, the prisoner was forced  to keep stepping up or risk falling off, similar to modern stepper machines. Meanwhile, the rotation made gears pump out water, crush grain, or power mills, which is where the name  "treadmill" originated. These devices were seen as a fantastic way of whipping prisoners into shape, and that added benefit of powering mills helped to rebuild a British economy decimated by the Napoleonic Wars. It was a win for all concerned, except the prisoners. It's estimated that, on average, prisoners spent six  or so hours a day on treadmills, the equivalent of climbing 5,000 to 14,000 feet. 14,000 feet is roughly  Mount Everest's halfway point. Imagine doing that five days a week with little food. Cubitt's idea quickly spread across the British Empire and America. Within a decade of its creation, over 50 English prisons  boasted a treadmill, and America, a similar amount. Unsurprisingly, the exertion combined with poor nutrition saw many prisoners suffer breakdowns and injuries, not that prison guards seemed to care. In 1824, New York prison guard James Hardie credited the device with taming his more  boisterous inmates, writing that the "monotonous steadiness, and not  its severity...constitutes its terror," a quote many still agree with. And treadmills lasted in England until the late 19th century, when they were banned for being excessively cruel under the Prison's Act of 1898. But of course the torture device returned with a vengeance, this time targeting  the unsuspecting public. In 1911, a treadmill patent  was registered in the U.S., and by 1952, the forerunner for  today's modern treadmill had been created. When the jogging craze  hit the U.S. in the 1970s, the treadmill was thrust  back into the limelight as an easy and convenient  way to improve aerobic fitness, and lose unwanted pounds, which, to be fair,  it's pretty good at doing. And the machine  has maintained its popularity since. So the next time you voluntarily subject yourself to what was once a cruel and unusual punishment, just be glad you can control when you'll hop off.