Like millions of other Americans, I don’t get enough exercise. I’m more keenly aware of that fact in the month of January, when every gym and athletic goods store ramps up their advertising efforts to take advantage of the New Year fitness fever. But that doesn’t mean I’ll do anything about it. Ultimately, it’s just not that important to me. For some people, the opposite is true – exercise is one of the most important things to them. Does that mean they have an exercise addiction? How do you know if you’re over-exercising?