[jslatts]

This is dead on. Almost every mountain bike ride I go on gets me into a state of flow where I'm not thinking, just doing. It does happen when I run as well, but generally external conditions have to trigger it (awesome music, beautiful day, great views, etc). This feeling is usually accompanied by a general feeling of happiness and punctuated by occasional thoughts of how great and lucky I am to be alive and able to participate in these activities.

I never considered that euphoric feeling during exercise to be the "runners high". I always thought it was the euphoric and satisfied feeling I have _after_ exercise that is the high. I pretty much always feel great afterwards unless I really over exerted myself.