T. rex biomechanics

[ptnorton <ptnorton@suscom-maine.net>]

I've read all the papers by Hutchinson and Alexander relating to the hip and 
leg biomechanics of T. rex, but still have what is probably a relatively 
basic question. This is no fault of their fine work by any means; they just 
didn't address this specific point.

If a T. rex was standing still and had to rotate its upper body downward in 
order to pick something off the ground (either with it arms or its mouth), 
would the muscles that were subsequently called upon to elevate the delicate 
little guy's upper body back towards horizontal equilibrium be the same 
muscles that generated dynamical running forces by flexing (i.e., pulling 
backwards) the femur? In the free body biomechanical diagrams I've been 
playing with recently it appears that, given the overall architecture of T. 
rex, both actions would essentially rely on the same muscle groups.

Anyone have any thoughts on this?

PTJN