It depends on the prison and how secure their maximum security facility is.
Some Maximum Security Prisons such as the ADX Florence prison the prisoners in their have to stay in their prison cells for 23 hours out of the day with just one hour outside in a rec cage for recreation.
So yes basically they stay locked down for 24 hours per day and when they do come out of their prison cell they're handcuffed and escorted to the rec cage by about 3 guards for one hour and then returned to their cells.
The cells at ADX Florence contain the shower inside the cell itself so they don't have to leave the cell to even take a shower.
The prisoners at ADX Florence are fed through slots in the door so they don't even come out to eat.
Other prisons may let the prisoners leave their cells for most of the day to do some work on a work program within the facility even if it is maximum security.
It just depends on the prisons.