I found the same thing... "not a good choice for most endurance athletes" ... before posting. That's why I did. My doc knows how much I ride and my lifestyle. We play soccer together. I even made a point of reminding him exactly how many miles and at what pace I ride while he was filling out the perscription. He said it shouldn't be a problem. I'm supposed to take it for three weeks and go back, so I guess I'll know more after a few days and a few hard rides.