Thanks for the advice, Jobob. I do put GU2O in my 100 oz. Camelbak, so I'm getting electrolytes and calories. Then I have an Accelerade or Endurox when I get home, which helps a lot. Last year I was having horrible problems getting sick after rides- I'd come home and have a headache for 24 hours. I came to the realization that because of my body weight and the fact that I'm a big sweat-er anyway, I need to drink A LOT, and I need a constant source of calories and electrolytes for any ride over 30 miles, depending on the temperature. Not sure what's causing the cramping. I think I'm pretty deconditioned at the moment because of my knee injury, so a long ride in the heat just takes it all out of me.