at a speed that is slow to those of us in middle age 
(ROOT (PP (IN at) (NP (NP (DT a) (NN speed)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ slow) (PP (IN to) (NP (NP (DT those)) (PP (IN of) (NP (PRP us))) (PP (IN in) (NP (JJ middle) (NN age))))))))))))
(ROOT (PP (IN ) (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (ADJP (JJ ) (PP (IN ) (NP (NP (DT )) (PP (IN ) (NP (PRP ))) (PP (IN ) (NP (JJ ) (NN ))))))))))))