Too many sets! The first set, and how deeply you attack/affect the leg fibres, sets the tone for the whole work out. I don't mean HIT, but you should go for maybe 2 big exercises - squats, hacks, leg presses, etc and rotate them weekly - and do 3 'good sets' apiece, so that you need the stair railing when you leave. I find that if you can't rip'em apart in that number of sets, you better re-assess your training -ie. poundage, ROM, feel. Best