Question:
Can riding hard cause the digestive tract to go into turmoil?
Background:
I have been bike commuting for 4 years. My commute is ~40 miles round trip. I average above 20mph which for me is sustained 70%-90% effort for 2 hours (1 hour each way). I ride 2-3 days per week.
Result:
On days when I ride, I experience "fast bowels". By that I mean I must visit the stall at work every 2 hours. Also, I get above normal flatus. I wouldn't go so far as to invoke diarrhea, but it is definitely a disruption to my day (without mentioning the chaffing).
I have tinkered with the cause, and the only thing I change is the ride. My diet is not altered between riding and non-riding days.
Am I the only one, or is this a known side-effect of cycling?
Pet hypothesis:
On my riding days, my body's caloric demand obviously spikes. In an effort to fuel the high demand, my digestive tract goes into overdrive - trying to pull as much energy out as quickly as possible. The result is inefficiencies; food arrives in the lower digestive tract partially digested. The bacteria there goes to work on it which results in the described side-effects.