He sat up, trying to free himself.
( He ( ( ( ( sat up ) , ) ( trying ( to ( free himself ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VBD sat) (PRT (RP up)) (, ,) (S (VP (VBG trying) (S (VP (TO to) (VP (VB free) (NP (PRP himself)))))))) (. .)))
He was trying to break free while sitting up.
( He ( ( was ( trying ( to ( break ( ( free while ) ( sitting up ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VBD was) (VP (VBG trying) (S (VP (TO to) (VP (VB break) (NP (NP (JJ free) (NN while)) (VP (VBG sitting) (PRT (RP up))))))))) (. .)))