So what would western medical texts refer to the lower dantien? it is actually describing several muscular structures working together, correct? Or is it actually it's own unique "muscular ball"?
So my anatomy for martial artists spent much more time talking about pressure points and the nervous system than the musculature.
This post on rum soaked fist
is probably better than what I would have said in terms of muscles, however it does little to explain the ball of movement you can see in Forrest or others demo's, even if they discuss the ball like pressurization.