One of my best girl friends used to be a personal trainer. My pants did not fit me quite the same way when we got back from our travels, so I called her. She told me to run for 30 minutes, do 3 sets of 10 lunges, and 3 planks held for 1 minute each, every day for 2 weeks.
I stuck to it, except on the days I did yoga or surfed more than 1 hour, I skipped running.
Lo and behold - my pants fit!!! They really fit!
I realize this has nothing to do with photography, but this worked so well I simply can't keep it to myself. Give it a try if you feel so inclined and let me know how it works for ya.
Or, you can just agree to ride your back well into your gray years and stay healthy that way, like this lovely Italian woman here.