Runner's Bowel Syndrome

When a person runs faster or longer than they're accustomed to, they might have sharp, sudden urges to defecate. The defecation is usually diarrheal, and the runner feels greatly relieved afterwards.

(2 Men are running in the woods.)

Man #1 - I can't believe we've ran for 10 miles!

Man #2 - Neither can I. But can we stop soon? I think I might be catching Runner's Bowel Syndrome.