The history of the treadmill is long and gritty, with a strong association with labour. There’s evidence dating back thousands of years of animal and human-powered models being used to lift heavy weights.

But by far the darkest chapter in the treadmill’s history came in the 19th century, when it numbered among the cruellest forms of punishment available. If you thought your first day back at the gym was grim, wait until you hear this.

In 1817, an engineer called William Cubitt was inspired by the sight of prisoners sitting idle to create a new machine. He thought that his invention, the “tread-mill”, might “reform offenders by teaching them habits of industry.”

Cubitt may have come from a family of millwrights, but his invention was designed to “grind air” rather than corn, with resistance provided by a system of weights.

19th-century penal treadmills resembled large, wide wheels fitted with steps. Prisoners sentenced to “hard labour” would climb the steps repeatedly, causing the entire wheel to rotate.

Cubitt's treadmills were fitted with hand-held bars for support, and most were large enough to allow several men to climb at once. Some, like the treadmill at the Vagrants Prison in Coldbath Fields, were fitted with partitions so that prisoners were isolated and could see only the wall in front of them.

The penal treadmill was “the perfect punishment” by Victorian standards, according to academic Vybarr Cregan-Reid. The work the prisoners were doing was “literally pointless”. It was a useless but exhausting task that fitted with Victorian ideals about atonement achieved through hard work.