Liberty Mutual/UPS Albany was a big proponent of work hardening. It works. I would start at 2 hours, work up to 4 hours a day 5 days a week. In between using the treadmill and machines, I would carry boxes with different weights inside down/up the stairs(on the second floor)-on a handcart-and walking various distances depending on the weight. If the secretaries needed a box carried, I would do it.
Liberty/UPS bought me a membership to the Y, while I am waiting for surgery. My case manager has always fought these in court, but actually asked me if I wanted one. I have proven myself to him. He knows I am not 'working the system'. I go 4-5 days week. I am in better shape now, then when I was 20. I have a 2 pak!!!!! I can almost see the next 2. Almost a 4-pak!! I've never had abs. I wasn't fat, just never defined.
Work hardening isn't for everyone. It all depends on the injury. Back injuries should be mandatory.