When the muscles contract, they pull on the bones, causing them to move.
(they; pull; on the bones; T:When the muscles contract) Context(they pull,List([27, 36))):(they; pull on the bones causing; them to move) Context(they pull causing,List([27, 58))):(them; to move; )
they pull,List([27, 36)) they pull causing,List([27, 58))
they they them
pull pull on the bones causing to move
on the bones T:When the muscles contract
them to move