That is what's most important. After he runs 5K's or 10K's, my boyfriend often gets sick to his stomach. Get the best athletes in the world together and you have a collection of the worst doctors on the planet. We athletes think we know everything, and we'd each offer a different answer to your question. But believe me, the answer you want must come from a doctor.
Experts say it's possible for exercise to interfere with digestion.
Sometimes for a race we go that extra mile and put extra stress on our bodies. Your boyfriend should get a checkup. It might be tough to persuade him to go, because athletes think they know it all. Then I found they knew more than my trainers. For example, many athletes foolishly practice dehydration.