Long distance runners have nothing on an office worker when it comes to stamina. Any cube sitter worth his weight in endurance can withstand maintaining the same “resting” position for up to three hours before even having to get up to use the facility (going to the bathroom is, after all, extremely frowned upon in the gulag).
The only problem with this very specific sort of skill is that, when you rise from your desk at last, your body tends to get a position shock from the act of actually being permitted to straighten itself into a standing pose. Thus, soreness and poor circulation are part of what your job pays you for. Like a reverse version of a coal miner, it is an over-engagement of inactivity that will fuck you up in an office setting.