engaging enough to keep you from shifting in your chair too often 
(ROOT (S (ADJP (VBG engaging) (RB enough) (S (VP (TO to) (VP (VB keep) (NP (PRP you)) (PP (IN from) (S (VP (VBG shifting) (PP (IN in) (NP (PRP$ your) (NN chair))) (ADVP (RB too) (RB often)))))))))))
(ROOT (S (ADJP (VBG ) (RB ) (S (VP (TO ) (VP (VB ) (NP (PRP )) (PP (IN ) (S (VP (VBG ) (PP (IN ) (NP (PRP$ ) (NN ))) (ADVP (RB ) (RB )))))))))))