[Sad Panda]

Here's what happens (and if I'm wrong, someone please correct me. I'm just doing this off the top of my head, so I don't expect to be 100% right about all of the details):

THC is fat-soluable, meaning you can't pee it out like you can with alcohol. Granted, some of it may remain in your bloodstream, but usually is only detectable for about 30 minutes (or so). The majority of it gets stored in your fat cells as it is broken down into another substance (I forget the name).

When you excersise, you raise your metabolism. The process of converting THC to the other substance happens quicker. This is why eating a lot when you're baked sobers you up. Eating also raises your metabolism, but not by nearly as much as excersise.

Basically, excersise just speeds up the body's natural process of getting rid of THC and all the stuff it gets broken down into, as well as your body's metabolites that break it down (these metabolites are what drug tests test for...just a natural product of your body, but one that only gets made to break down THC).

Anyway, for a casual smoker like yourself, you would be clean five weeks after you last smoked whether you excersised or not.