There's no real big difference for me, but it definitely makes it harder to push yourself most of the time when you'd rather be laying on the couch.

I think it's almost a waste of a smoke anyways, since any physical activity brings down your high. Why not wait until afterwords and enjoy it that much more?

If you're worried about it being bored, grab your mp3 player (granted you have one) and just go lift, run, whatever. Smoke afterwords and make it last longer than what it would be if you did before working out. ~