Has anyone experienced cronic abdominal cramping during (specically x-c) races? I'm talking cramping that doesn't go away, but gets worse as the race progresses and forces the runner to slow down to the point of adding 3+ minutes to their 5k race time. It doesn't happen every time, but has happened multiple times over the course of the past few years. Also, it never has happened during the track season, nor is it a problem during practice. Any advice on what might be causing this, how to prevent it, or how to deal with it when it does happens would be appreciated.