With everyone I believe the movement is more important than the load. Build quality, and the quantity will come. This is simply more true for people with relevant injuries than for entirely healthy people, especially since entirely healthy people are vanishingly rare. Almost everyone's got something wrong with them, it's merely a matter of degree.
Getting people to begin is the first big issue. But if they do begin then at some point later on it gets hard, getting them past this is not easy. At some point come the grindy reps and the prospect of being buried under the weight. Everyone thinks about weaseling out at this point, whether they have previous injuries or not. "Kyle actually I'd like to work on cardio for a while... also I'm getting a twinge just here... and... well training is kinda expensive... and..."
The barbell works. But it's not easy. But then, as we were told in the army: the easy way is always mined.
