Over the years, being a rep for a large camera company, I always carried a lot of gear and it was not unusual that my camera bag held 30 to 40 pounds and that was usually hanging from one of my shoulders.
I am not saying that was the only cause of my terrible and painful post surgery lumbar area because there were probably many things that contributed to that. But all that heavy camera gear on one or the other shoulder was a major contributor.
The article I am linking you to is very educational and written by someone who knows what carrying camera gear can do to the human body, whether it is on your shoulder or on your neck.
He stresses the benefits of lighter gear as well a a preferred method of carrying which would be more around one’s waist but does not discount backpacks as well.
My choice for around the waist is pretty much known. It is bags made by Cosyspeed. Other methods which relieve stresses on the spine are offerings from Scott Vest and Peak Design.
My three ways of carry: