I haven't raced that soon after a colonoscopy. I think the bigger concern would be if they remove some polyps, which might irritate the colon. Otherwise, regular diet plus possibly some lactobacillus acidophilus (can be gotten through many brands of yogurt or pills) should get you back to normal in a couple days.
ACTIVE is the leader in online event registrations from 5k running races and marathons to softball leagues and local events. ACTIVE also makes it easy to learn and prepare for all the things you love to do with expert resources, training plans and fitness calculators.