Thank you for your input on these things. I don't know what "prolotherapy" is, so I'll have to do a net search on that one. That psoas muscle you speak of, (which I believe is refered to as the "hip flexor" muscles) are the reason why I perform the the stretch with one knee at a time pulled into my chest while laying on the floor. This stretch keeps that muscle flexible.
Now as far as the spine and supporting muscles of it NOT being designed for a lot of bending goes, well that is precisely why dead lifts aren't really a great exercise for long term overall lower back and spine health/strength. The only thing I know for certain my friend is that when I herniated my L5 disc and I was in my mid 20's, the doctor told me that the injury wasn't bad enough to warrant surgery even though i was in a lot of pain, but that I will need to get a desk job by the time I'm 35 yrs old. But I proved him wrong because I used the couple stretches I've mentioned along with back hyper extensions to rehabilitate my lower back. And I haven't even needed to visit a chiropractor now in over ten years like I used to. I perform standard barbell squats without pain, and without a problem, and I also continue to perform the back hyper extensions too. But NO dead lifts for me. That would be inviting back injury.
What I learned over the years is that muscle spasms are a major cause of back pain, and they can last for a couple hours to a couple months at a time. If your back muscles, ( or any muscles for that matter) are not flexible, then you will definitely be much more prone to muscle spasms. Stretching has allowed me to avoid the pain and muscle spasms that I experienced for years after I herniated my L5 disc. Before I began stretching, I couldn't even sit down on the toilet for ten minutes to defecate, without having major pain from merely trying to stand up again. All that is history now for me, and I never had back surgery.
One other thing that I neglected to mention: I walk a lot in my work place since the factory building that I work in is literally one half mile long. And the walking also helps to keep the lower back muscles loose and flexible. I know this because if I take a long four day weekend off from work, and I don't go for a daily walk, my back feels considerable tighter than usual. So walking every day helps too.