3 days and about 100 e-mails ago I wrote...
Now I have tried it. I encourage imitations. Results:
- It's easy. The necessary effort is pretty low. All that remains is to pull one's legs (no pun intended!) forward quickly enough (rather than to pull the entire body forward and the legs backward against the ground).
- To get really fast, one needs big preacetabular iliac blades, big cnemial crests and big muscles in between; this is what determines top speed. Tyrannosaurus has that, much more so than I, of course. I haven't tried to get at my top speed (but I did run), largely because I was afraid of falling on my nose, but that shouldn't be a problem when a reasonable tail is present.
- It slowly begins to hurt. Needed are robust joints -- shock-absorbing cartilage comes in handy, as does the arctometatarsus that can withstand stronger impacts than my ankles.
- Getting around curves is not very easy, but should be when a reasonable tail is present.
- To brake quickly is a problem; I can brake easily by rearing up again, but such a vertical posture is precluded to theropods. The knee-extending musculature and the feet are stressed a lot. An obvious solution is to let the prey do the braking, as suggested by the famous bite-strength study of Allosaurus. Cheetahs also brake (partly) by throwing their prey to the ground.
- I was unable to determine whether kangaroo-style achilles tendons could save energy, as I remained plantigrade. My shoes are too small in front, so my toes hurt. :-)
Too bad I didn't get any numbers out of that. :-)