Somebody care to highlight data that supports this? I'm acquainted enough with the notion that the ideal pack load rest on your hips, but I was under the impression that the purpose of a backpack (in particular the shoulder and sternum straps) was to orient the load's center of gravity as close to the body as possible. This seems like, while it puts the weight on your hips, the center of gravity is further out from your own, creating additional effective strain than you might get.