When our bones are used, and our muscles pull and push our bones- the bones are stimulated to build up their density&#150; the building 
(our bones; are used; ) (our muscles; pull; ) (our muscles; push; our bones) (the bones; are stimulated; to build up their density&#150; T:When our bones are used, and our muscles pull and push our bones) (the bones; to build up; their density&#150)
our bones our muscles our muscles the bones the bones
are used pull push are stimulated to build up
our bones
to build up their density&#150 T:When our bones are used, and our muscles pull and push our bones
their density&#150