This TOJ was reading a book by Nassim Taleb called Antifragile: Things That Gain From Disorder. He's best known as a brilliant, contrarian financial risk manager. However, he's also one of those broad thinkers who looks to other fields for insights to shed light on his work and life, including his choice of exercise - power lifting.
While doing some research he ran across a an 2003 Science article by Gerard Karsenty, a cutting edge scientist, who believes that bones are not just like passive metal beams in a building, but are very metabolically active, producing a host of chemicals that work at a molecular talking to other organ systems in the body. It's likely that bones play a key role whether or not you're healthy, not just whether you have bone related maladies as you age like osteoporosis or arthritis, but even diabetes or loss of sexual function.
At the heart of Taleb's argument is that we, the civilized and industrialized welfare staters, have developed an aversion for stressors of all kinds, in particular physical stressors. And this has been detrimental to our health and well being. Ironically, as we age, we're supposed to be more careful in order to avoid injury, but what we really need to do is be more aware of our limitations then consistently challenge them.
This TOJ thinks Taleb is right on the money. We become fragile (decrepit) earlier in our lives than necessary because we don't do the physical activities that will keep us strong and robust. The bones are very complex and not as well understood by science as you'd think they'd be. But one thing they do know, though they can't fully explain how it works, is that if you stress your bones the "right" way, they get stronger.
Once they thought only young bones reacted this way to the mechanical loading from exercise. However, more and more research shows that everyone of all ages benefits from using gravity and/or additional weight to stimulate the bones to grow stronger. Check out this successful program for older women at Oregon State University called Better Bones and Balance.
You'll see that the OSU program includes exercises that involve stepping and jumping to place a brief mechanical stress on the bones. Here's an interesting article by C.H Turner and A.G. Robling that explains what might be going on. Worth noting from their research is that you'd don't need to overdo the jumps. In fact, the bones respond better when exercise sessions are split; they observed if you do are going to do 120 jumps in a day, you see a 50% increase in the osteogenic index, a measure of bone formation, if you split the jumps into two 60 jump sessions separated by an 8 hour rest.
We TOJs are anti-fragile. We do our bones a favor and take some calculated risks. We seek positive stressors. We're jumpy.