True story time....
I attended Colorado State U in the 80s. During that time there was a Master of Science student who designed a study which was supposed to gather evidence regarding any relationship between exercise and bowel transit time.
BTT is relative because, in theory, the longer digested food remains in your GI tract, your chances for getting cancer increase.
Evidence from that study indicated that exercise conducted at age predicted heart rate levels does decrease BTT, thus reducing the time food remains in your gut and therefore decreasing your chances for GI related cancer.
The subjects were asked to swallow whole peanuts, then wait for the peanut to show up in their poo.