How to avoid back pain as we age

I recently heard a radio interview with a doctor who was discussing a number of age related health issues. He said that as people get older they tend to only stand up and sit down (the two positions we are in most of our waking life) so the muscles in the back tend to shrink and harden. Then when the person does something, turns a certain way or picks up something and over extends the muscles, the person ends up with back pain.
We need to remind our young people to continue stretching and moving their bodies (like they did when getting ready for sports or gym class in high school.) Stretching keeps the muscles long and flexible. Also they say "long muscles are lean muscles" (stretched and toned muscles tend to not collect fat.)

So many people have back problems nowadays, we need to warn the next generation how to avoid it as they get older.