Answer:
The treadmill
Explanation:
Two hundred years ago, the treadmill was invented in England as a prison rehabilitation device. It was meant to cause the incarcerated to suffer and learn from their sweat. It would mill a bit of corn or pump some water as a bonus. In the 19th century, prisoners sentenced to hard labour walked the treadmill for at least six hours daily, the equivalent of climbing 10-14,000 vertical feet. ... This way, the prisoners would be working for the benefit of wider society.
