Do you spend the other 23 hours in an 8x5 room with cement walls and nothing but a bed and a toilet?

23 hours involuntary solitary confinement is legit confirmed psychological torture. Self-inflicting that is either self-harm or else you are doing meaningful activities indoors and it's not the same thing at all.

But you have a choice to spend less than an hour outside.

Are you spending the other 23 hours sleeping or standing? Because that’s what solitary confinement is. You get to do nothing but sleep, walk around, or use the toilet.