Re: T. rex biomechanics

[Martin Baeker <martin.baeker@tu-bs.de>]

> 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.

If you just think of muscle groups (i.e., if you lump all femur
extensors into one big pseudo-muscle, like Hutchinson did in the
Nature paper with Garcia), you are right, I think. However, since
there are several muscles involved, it is not too clear that it would
not be some other *specific* muscle in the femur extensor group that
might be involved. In addition, there might also be antagonists
coming into play to stabilise things. Simple experiment: Sit down on a
chair and slowly get up. Note (by putting your hands there) that both
your femur flexors and extensors are involved (i.e., muscles on the
front and the back of your femur are creating tensile forces). To
understand exactly how a Trex raises its upper body would require to
look at all these muscle groups. There are some papers by Hutchinson
on detailed muscle group studies of T rex, but so far, I think, nobody
has looked in detail at this particular movement.

Hope this helps,

Martin.


                   Priv.-Doz. Dr. Martin BÃker
                   Institut fÃr Werkstoffe
                   Technische UniversitÃt Braunschweig
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                   38106 Braunschweig
                   Germany
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                   e-mail <martin.baeker@tu-bs.de>