This is the racetrack.
Every 2 hours, you're allowed ("allowed" is good – the wardens lurk around with whips….) to walk the length of the corridor and then back to bed.
Not as easy as it sounds.
Given that when they replaced the crook bits with titanium, they also buggered around with the thigh muscles and made some stuff disappear totally, so that your foot flops around with a mind of its own and you have to force it straight as well as concentrating on which crutch to use for which step.
And not look down.
Or fall over.
And avoid the other 30 or so folks in various states of perambulatory disrepair who are doing the same thing……