( These ( ( ( need ( no stimulus ) ) ( to contract ) ) . ) )
(ROOT (S (NP (DT These)) (VP (VBP need) (NP (DT no) (NN stimulus)) (PP (TO to) (NP (NN contract)))) (. .)))
These need no stimulus to contract.
(ROOT (S (NP (NNS Muscles)) (VP (VBP need) (NP (NN stimulus)) (PP (TO to) (NP (NN contract)))) (. .)))