What Does Hitting the Wall Mean?

When we start exercise, our stress response kicks in and so the drenlin and the nor drenlin that i spoke of earlier suddenly send little signals to say to the body, start producing energy. The consequence is that we send the glucus that was stored in the liver into the blood stream. And then it kind of stays there because we achieve a new level of balance. It's higher than it was, but it stills constant. Only if we go for hours without replenishing that that first starts to be under strain. When that happens, and this is a sure sensation familiar to everyone, we start getting light headed, tunnel vision, maybe a little bit sweaty, weak.