When I was a kid my mom would get really upset about how heavy our backpacks were for school, because she thought it was going to cause us back issues. Was kind of a long walk home, especially jr. high and high school 'til we turned 16.
Now in college I carry heavy books, a laptop (with charger, external HD and all that) and just whatever. It's pretty heavy, and I like walking around to the different buildings when the weather's nice and there's the time between classes for a little extra exercise. It does hurt my back though. Sometimes I wish I brought my giant like hiking backpack instead of this smaller one, because it has the belt strap and tons more padding to make it comfortable. That belt strap helps a lot, keeping the weight distributed better.
yeah.