Sure, working out can sometimes feel like a punishment. So it's not exactly surprising that, according to a new Ted Ed video, treadmills were actually created for that very purpose. We knew it. As the video explains, conditions for prisoners were pretty horrific in England in the 1800s. If they weren't executed or deported, prisoners spent their days totally alone in gross cells. So, in response to a social movement to help improve prisoners' lives, prisons started implementing the use of some truly torture-like exercise machines. Originally, these took on a more Stairmaster-ish appearance: A giant spinning paddlewheel with spokes for prisoners to step on. As it turned, prisoners had to keep stepping, or they'd fall off. But all their work wasn't wasted — the paddlewheel turned gears that then did things like pump water and crush grain. They also powered mills, which is where the term "treadmill" first came from. So, treadmills were helpful and kept prisoners moving — but maybe too much. The video says that prisoners spent approximately six hours a day on those things, equivalent to walking up to 14,000 feet per day. That, combined with a poor diet, often left them with injuries or breakdowns. Luckily, the original treadmills were pretty much done away with by the end of the 19th century. Then, a more modern version (closer to the ones we subject ourselves to now) first appeared in the 1950s. And after the jogging craze of the '70s cemented treadmills' popularity as fitness machines, here we are. So, even though a half hour of intervals can feel pretty rough in the early a.m., just be glad you're free to follow it with a protein-packed snack (and maybe a nap?) if you so choose.