The Cyberspace Age. Healthy?

I would guess that the average American person, ages 5-30, sits in front of a computer screen, phone screen, television screen, or any other 'cyberspace related screen' for 4 to 5+ hours per day. I know I am guilty of far higher numbers all too often. What are the consequences of this? There must be a mix of both positive and negative effects. Were our bodies designed for this nearly constant atrophy of most of our muscles? Do we even realize as a national (and in turn global) community what this may mean for the average person's health? This topic needs to be studied more densely and far more often, being as that we are clearly in the midst of what I (along with many) like to refer to as "The Cyberspace Age."