What would be really cool was if you were in good shape (as some others here are as well) but also put your foot down appropriately. You know, kind of an "I'm in good shape but I'm not stupid" sort of thing.
I guarantee your job requirements do not say that you need to be able to lift 150, 200 lbs. We should be able to perform according to our job description. Beyond that, that's what machines and extra sets of muscles are for. IANAPM. I am not a people mover. I have never had a back injury at work, but one day when I was holding up a load probably twice my body weight, I just decided that was the last time. And it was.
Get your peers involved and change the atmosphere. Go help people when you see they're about to do something they shouldn't be doing and say, "Take care of your back, you need more help for this. Let me get a couple more people; BRB." Etc. Pretty soon people will get on board with not single-handedly lifting, pushing, pulling, dragging and scooting awkward loads 100, 200, 300, 400 lbs. The number of times people are doing these things and there isn't even an emergency of any kind...nah, that is just dumb.
It is not okay for a workplace to not have the proper tools to move the loads that need to be moved and to rely upon knowing that we gluttons for punishment will simply martyr on, serving as the people-moving machines that the employer didn't want to spend money on.
You could choose to use your strong physique for lots of other people's good, if you wanted to...Be a strong one who demands a change. Then, along with your exercise/health routines, you'll have a chance of your back being good for a long time.