Decent read, lots of medical references, and all good information. Only thing is, he (and you) are suggesting barbell training for people with lumbar pain. NONE of his references specifically cite BARBELL training, and they certainly don't support loaded full squats, they cite resistance exercise. Barbell training, specifically putting a bar on your back(across you shoulders or chest) GREATLY increases both compressive and shear forces in your lumbar spine, and is VERY dangerous for someone with lumbar pathology.
Now, as a "wise" man told me today, hopefully no one is actually implementing medical/rehab advice that they found on a golf forum. I truly hope that anyone experiencing back pain consults with their MD before starting an exercise program, and then they seek out professional therapy from a licensed Physical Therapist who will help them regain mobility and , most importantly, STABILITY in the area, and only then begin to strengthen.
And now I think we may be officially "off topic". :~(