the problems i see are two fold, though i'm sure there's more science-reasoning out there:
1) you're taking something that makes you less aware of pain you're feeling, pain which may be your body's way of saying "this particulary move/way of doing this, doesn't feel right." that's a set-up for injury.
2) lifting heavy things is designed to provoke a short term inflammation (not chronic!). you're blunting that effect, and thereby blunting the point of the exercise.
basically, if something hurts too much when you do it, you probably should figure out a different way of doing it. pain is a signalling system for your body, and not something to be ignored.
"dean ornish and dr. davis think the palmitic acid our bodies use for fuel while we sleep is poison if we eat it. zero-carbers like charles washington think the oldest fuel in our evolutionary history – glucose - used by organisms a billion years ago and without which the brains of modern mammals cannot survive for more than a few minutes – is an unnatural toxin if you eat it. both views ignore basic facts of medical physiology and defy evolutionary history." - kurt harris