Why does it happen? It feels like my Appendix is trying to make a break for freedom, I often just ride through it.
I've kept my fluid intake as low as possible and don't gulp it down either. could it be the Energy drink I am using?
From what I can remember no-one really knows much about it, I can only suggest that you do some reading up and try and find a solution that works for you. The technical term is: exercise related transient abdominal pain
I saw a tip in Mens Fitness for fending off stitch; they suggested that you breathe in such a way as to exhale as far as you possibly can, then inhale as far as you possibly can. I forget what they called it, but it definitely works for me when I'm running.