Is that trained or untrained? "Newbie gains" is a real thing, mostly caused by people going from a negative health state to a "normal" health state (or inactivity to basic activity).

I can see a rapid increase in untrained people but more marginal increases in trained people because of this.

I was under the impression newbie gains were more attributable to better neuromuscular and connective tissue adaptation rather than something that can lead to bone growth. You can gain like 2-4lbs of muscle per month in that phase, and a disproportionate amount of strength.

A 40% increase in bone density over 6 weeks sounds like someone’s DEXA scanner is broken. Bones just don’t change that quickly.

Is there a case of bone density being "too low" in some sense that can cause it to go up more quickly? Maybe it's not the bones themselves but something the DEXA scanner picks up that looks like bone growth?