I never swung an etrac so can't compare to AT pro, but I will say this, having swung an AT pro for about a year, it is not what I would recommend to someone who has a back problem. Great performing detector, but the weight and balance did put stress on my arm and back. I went to a really lightweight machine, but I would not pay over $1000 for a detector just because of the light weight and am not suggesting you do that, just a point of discussion (i.e., I moved away from the AT Pro primarily because of the weight and balance). There are other detectors out there in the same price range as the AT pro that weigh similar, perform similar, but are better balanced to take stress of the back and arm than the AT pro, I am not going to name them in a Garrett thread. If you already have the AT pro and it feels better than the etrac, go for it. If you have not purchased it yet, I highly recommend getting a demo unit and swinging it for a couple of sessions to see if your back indeed feels better than swinging the etrac, but I would be surprised. A swing harness, as suggested, is a good idea if you are really uncomfortable and I would recommend it even for the AT pro. I think even the AT max is a little lighter and better balanced than the AT pro and addresses some of the shortcomings, so that might be a better investment at this point.