When I switched from Curves to 24 Hour Fitness I used to get lightheaded, I assume from the more intense exercise. But it was only when I was exercising, not when I was just standing.

I've only come close to fainting once in my life, and that was when I gave blood. I felt naucious (sp) after they were finished, and while walking to the bathroom with my eyes open everything went black. I remember my eyes being open and being unable to find the knob on the door! Someone opened the door for me and laid me on the floor. I threw up and then felt better.