Jason, how do you deal with the physical compaction of the spine with those drop loads on your shoulders? Or does the act of passing through to the ground, actually involves extension of body alignment such that it naturally averts the compaction the spine?
I can't really answer that on any technical level, but it just doesn't seem to be a problem for me at this point. Early on, when I first started doing this, and had to really work at relaxing my lower back (due to the back injuries), I would definitely feel that my lower back was being strained (not in a bad way, more like worked hard) when I would consciously relax my lower back/spine and do things. That fatigue seems to have passed and I guess that my body has just adjusted and gotten stronger. I would think at this point if it were going to impact my spine in a negative way, I'd be feeling it by now, but the exact opposite has been the case. My lower back feels better and stronger now than it has at any point in the last 15-20 years.
My guess, and this is only a guess, is that it has a similar effect as focused lower back stretching, inversion, etc, in that it allows increased blood flow into that area of my back, which helps. I also think that the compaction gets regulated by the body as you get better at relaxing those big muscles and letting the less prominent muscles get stronger and handle the load. It probably wouldn't be good to just jump in and try relaxing your lower back with a big load on your shoulders, but much like any sort of weight training, you build up and increase and get stronger as a result.