wind up using them as punching bags 
(ROOT (S (VP (VB wind) (PRT (RP up)) (S (VP (VBG using) (NP (PRP them)) (PP (IN as) (NP (NN punching) (NNS bags))))))))
(ROOT (S (VP (VB ) (PRT (RP )) (S (VP (VBG ) (NP (PRP )) (PP (IN ) (NP (NN ) (NNS ))))))))