What is the most ergonomic backpack?

According to Dr. Holly Klopfer, DPT (a physical therapist in San Francisco, California), the most ergonomic backpack are Ivar packs. Doing a quick google search on ergonomic backpacks, here's a quote from Dr. Klopfer, DPT: "Ivar is the most comfortable and ergonomically correct backpack I have seen. Typical backpacks are terrible for your back. All the weight in the pack sits on your lower back. This is not only uncomfortable, but it's also unhealthy. Ivar's shelf design substantially improves weight distribution of your stuff, making it more comfortable and better for your spine." So, Ivar Backpacks seems to be an ergonomic pack, as validated by the above doctor's quote and other feedback on the ivarpack.com website. Other backpacks with ergonomic qualities might be JanSport's Odyssey pack, with the rubber honeycomb feature in their shoulder straps. Makes the straps squishy on your shoulders which is a little more comfortable. But still, when you load your stuff into The Odyssey pack, all the contents falls to the bottom and sits on your lower back. This is the key difference in an Ivar. The patented shelf design evenly distributes the weight among the shelves. I actually own both an Ivar Urban and a JanSport Odyssey. Both are great packs, but the Ivar is definitely designed for ergonomics over the JanSport.