Summary of “This Is the Effect Working Out Has on Your Bones”

Every year, about 10 percent of our oldest bone matter is expelled from the body and replaced by fresh bone, and exercise and sports can make that incoming fresh bone denser and stronger than it’d be if we just sat on the couch, says Michael Econs, a physician and member of the American Society for Bone and Mineral Research and a professor at the Indiana University School of Medicine.
Many articles will tell you this effect is all about “Building bone,” but calling it “Building bone” makes it sound like building muscle, and the effect isn’t quite that straightforward.
There’s an age cutoff by which bones can’t grow larger.
“‘If you think about it in terms of building a bridge that you can’t touch for 80 or 90 years, you want to build in a self-repair mechanism,’ he says, ‘so if you have a micro-crack, can come in and dig out the bad or old bone and lay down new, fresh bone.
Age-related bone loss percentage will be lower, and it’ll have a lower effect on the bone’s strength overall.
Nearly all studies and talk focus on elderly men and postmenopausal women, so when an organization such as the US Department of Health and Human Services says regular exercise increases bone density, the advice tends to be interpreted as “The sky’s the limit” and extrapolated to all ages and populations, giving false hope to people who want to turn their scraggly toothpick arm bones into those like the Croods’.
Dig a little further into that 2008 Committee Report, and you see that talk of bone gains is not about net gains-ending up with bones larger than when you started-but about stemming the loss of bone, or breaking even.
You work out to maintain what bone you have by adulthood, not to keep growing it bigger like a muscle.

The orginal article.