What does it mean if I have a really arched back like my gamer friends?

Don't know. These two concepts may not be related at all. You may have inherited an arched back or be known as a "swayback" which really is a normal condition when one has more curve in the small (sway) of the back than others. "gamers" are not known to have more arched backs that I have heard....If you have discomfort or concerns see your doctor for an exam and more information.