Oda Field - stomach cramps

Only did 2 runs at Oda Field last night. The plan was 1,200; 1,000; 800; 600; 400; 200. I just missed the start of the 1,200 but ran it midfield. I had an OK run in the 1,000 (but forgot my watch - no time), then my stomach started feeling bad in the 800, but I ran OK, but I knew the 600 would be tough. Somehow I figured going out even harder would make me forget the stomach pain, so I raced to the front in the 600, but at exactly the 400m mark I had to pull out. I couldn't line up for the last two. Not sure why I had the pain, I hadn't eaten since 1pm. Maybe I had drunk too much water near the race time.