I have an friend who is an old school, weightlifter, wrestler, retired policeman form Poughkeepsie NY. He's in his early 70's now, and cant really walk around much.
(Spinal stenosis). BAck in the 80's, a chiro cracked his back literally, and caused a spinal cord injury that had him immobile / in hospital for almost a year.
Some of them are really quacks (*cough* Franco)...