I've found that fairly ineffective with my condition (delayed sleep phase disorder). There's not much improvement at all when I'm working out regularly after work / on weekends to when I'm only doing it occasionally.

But then again, I'm fairly active at work (have to go up and down stairs between my office and the lab dozens of times a day, standing lab work, walking out to the warehouse to get parts, etc. which actually adds up to quite a lot, even if it's not very strenuous) so maybe if I just sat at a desk all day it would be a lot worse.