Hi. Thanks for your query. Noted the history and understood your concerns. Diarrhea after a bike marathon is not really known to occur due to strenuous exercise or so unless you have IBS that is irritable bowel syndrome. I would advise you the following: Send the sample of stool again. Watch for the source of water and foods may be an outside or stored foods or the preservative added food that can also cause similar problems. Identify the foods and beverages that instigate or enhance the problems as you are feeling queasy before passing watery diarrhea. Sometimes a course of an antibiotic, metronidazole and probiotics can help to solve the problems but needs a prescription of your Doctor. Take plenty of boiled and cooled water along with electrolyte solution to maintain hydration and electrolyte balance.