eating bananas during comps helps.. dont ask me how or why, but it works a treat! Last comp i rode, i cramped up soo bad took 2 fives, then ate a banana and waited bout 10mins, rode next section on a 2. Not great lol, but better than another 5. I find too that relaxing helps alot and try to flow more / less brake squeeze helps longevity before cramp sets in. good luck with it. i know its a curse for quite a lot of riders.