I started running a couple of years ago and for the last 18 months have been entering occasional races.
After every race, without fail, I go down with a cough/cold that wipes me out for 2 weeks - have had some of the worst colds of my life since I became "fit"
I'm assuming it's something to do with the increased exertion affecting my immune system, as training runs don't seem to have the same effect, but what can I do to prevent it?