Backs are tricky. I'm 6'1", but have an inseam of 31", which means all of my height is from my hip to my shoulders.... thats a lot of back! It doesn't help that I spent my better years moving pool tables and other types of vending machines up and down stairs before there was such a thing as a "stair climber". I can't count the number of times I've thrown out my back. I've been to doctors and chiropractors and had "therapy", and I have found one simple way that works for me. Stretching.
5 minutes of stretching every other day or so works wonders. I do only a couple. One, lay on the floor on your back, bring one knee to your chest (or as close as you can get for those chubby guys

) rotate it over your body keeping your shoulders flat on the floor 10-15 times. Once you get a bit more limber, extend your leg as your knee almost touches the floor for more stretch. Do the same for the other side.
Second is again on the floor on your back. Pull one knee up to your chest as much as you can keeping the other leg strait and on the floor. Hold it tight for a couple of seconds and release. Do 10-15 of these for each leg.
I've had my wife do these when she threw out her back and though she said she was sore she was up and running with in a day. Just picking my kids up when they were small could throw mine out, but now at 55 I have no fear of lifting kids or pretty much anything else. It's only a few minutes now and then but the benefits have been awesome.
Remember, I'm NOT a doctor, but this is what worked for me.