Originally Posted by Enthalpic
I agree it sounds more like a bug or food poisoning. Primarly because 5 hours later seems like too long of a delay for that type of problem. However, in the future for a ride that long use sport drink; not water.
OP you did 6 hours straight on a trainer? Talk about mental toughness!
My Tour Kit for Fast Across America by Bike says that "use of Sport Drinks only can lead to de-hydration".
I do not know any better. I avoided sport drinks because I wound up with contaminated water bottle on a long hot trip.
6 hours straight on trainer? No, I stopped one to two minutes every half hour to drink and eat.
I started this quest to see if I could do 100 miles in six hours at an acceptable HR. That worked, never got over HR 130. Used 85 RPM steady and averaged 16.7 MPH. That is why I drank so much water, to keep it cool. I guess too much water is not good. See the other respondents.