The symptom of peeing a lot during physical exertion is caused by a lack of sodium; often because the sodium that would be holding the water in has been sweated out. When that water can't be held in, whatever isn't sweated out will be peed out. Sodium helps the water stay in the system. Adding some sodium amount into your bottles will help you hold more water in and allow the water to be useful. It'll taste a little gross until you get used to it, but try adding some lemon juice and some table salt into your bottle before...