Can I do anything about them not honoring a doctors order?

Yes of course. You can do a lot of things.

You can quit. You can get another job. You could complain on YA if you wanted to. There are a multitude of things you can do. What do you want to do? What are you willing to do?

The list is endless. What are you going to do. The choice is yours!

The first thing an attorney, judge or jury will wonder is if your back was in such pain why you choose to lift something you knew you should not. An employer can say this is your job despite the note and you can always say I cannot do that you see the note.

Then, if they fire you for not doing the job you refused to do because of a documented injury you have the option of suing for damages. But once you choose to do what they asked above your limitations repeatedly you made any such claim null. Because they will argue if you were so injured why did you agree to do that job instead of protesting and sitting down.

Because, let's face it, you are a grown up. If you choose to do something you know will hurt your body despite the situation and unless they hold a gun to your head, you are responsible for the damage resulting from that action.

check with a chiropractor to see if a realignment is good for you. They are not doctors and don't give medications but they will put your back back in place for you. Rest (just do light duty so it doesn't fall back out of place). It should take just a few appointments to get you going in the right direction. Doctors only know their specialty, realignments aren't their specialty. So set that appt with a chiropractor ASAP and stop missing work.

First you need to take advil (to bring down the swelling because that's what's hurting and stop the medication from the doctor) after eating and then use cold packs on it. Don't exercise at the jym. You need for it to heal. You might not be able to go to the jym again (for exercising your back) if your injury was bad since heavy exercise will make it hurt and put it out again.

The employer did not honor the slip. You had a doctor's note and still did what you were told not to? If I was in the shoe when I returned to work I would have first shown the boss the slip. Here is where you'll find your answer. If you showed the slip and the boss told you to do heavy duty and you did it? Where you fired because you did the heavy duty even after you went to the doctor and showed the slip to the BOSS? Please don't forget, YOU KNEW, YOU HAD THE SLIP....

Your problem is that you did not follow doctors orders either. You could have refused to do heavy lifting. You did not. Thus you can be held at fault also. You were not injured at work but at a gym which started your back problem. Proving your work caused all subsequent problems is going to be difficult.

You could sue for compensation but your job might go in an instant. Then you could sue for wrongful dismissal. See a solicitor for advice. Go to a specialist in industrial law and preferably one that will take the case on a no win no fee basis.