When i do squats after 5 sets, not always but im runniong to the toilet to throw up.Heavy squats in my opinion are the hardest exercise in the whole bodybuilding routine but that no exscuse not to train legs avoid suats by all means but the leg press i find is the easyist exercise there is, leg extensions are not to hard on the body or are leg curls.
There is one guy at my x gym who had an incredible upperbody 20 inch plus arms huge chest and back and no legs he looked redicously unproportioned in saying that i have no respect for upper bodybuilders.