Earlier in the week, I read a comment that someone was having back pain from heavy camera and lenses.  I know someone suggested a shoulder strap, but I found a couple of things that might help, one is belt harness, so you have to be careful if your belt is just a decoration,

      http://www.engadget.com/2009/11/02/spider-camera-holster-system-lands-for-r..

     and another

     http://cottoncarrier.com/

     Of course outside of these two contraptions you might order a hot tub, which is more expensive for sure, or of course hire a camera bearer, "bwanna say had me that camera there", "Oh I know it's not mine, but I am only gonna use it for a few shots since I don't have a 400mm lens".