I used to have a lot of back problems through my 20's and 30's. Then when I was around 40 I started to do daily training. I reckon most of us are quite strong physically but piss poor in the core (I was !). In the morning before breakfast I do 100 chinups, 100 situps and 100 pressups. It is dead quick, I do it while the kettle is boiling. I did this for about 4 years, and then I added some in the evening, I do 100 chinups, but it is 5 sets of 20 and they are calisthenic chinups so much more technical. Now I am 48 and I havent had any back problems for almost 10 years, in fact I am in much better nick now then when I was younger. I also train karate twice a week and also try and run or cycle twice a week if poss.
Daily training is the key, I havent missed a day in over 8 years, even when I broke my ribs, I found something I could do and didnt stop.
The other thing is stretching. I hate it, but I know it does me good so I suffer through it. I think that this is probably as important as the exercise as you start to get older.