Re: Mamenchisaurus Posture Paper

[Roger Seymour <roger.seymour@adelaide.edu.au>]

Thanks, Kris, for letting me know when water was replaced with air in
g-suits.  I knews that pilots didn't slosh around in wet-g-suits
anymore.  Interestingly, you say that it is the arterial blood column
that is more important than blood pooling in pilots.  I found the same
thing in snakes where the vertical distance between the heart and brain
was twice as important as blood pooling and venous return from the tail:
116.    Seymour, R.S. and J.O. Arndt.  2004.  Independent effects of
heart-head distance and caudal blood pooling on blood pressure
regulation in aquatic and terrestrial snakes.  J. Exp. Biol. 207:
1305-1311.
Alan Hargens suggests that the tight skin on giraffe legs might operate
like a g-suit and facilitate venous return.  I think that he is
correct.  G-suits on sauropod legs might have helped too, but wouldn't
help the problem with the long neck.

MariusRomanus@aol.com wrote:
> 
> In a message dated 6/1/2005 3:49:42 PM Alaskan Standard Time,
> roger.seymour@adelaide.edu.au writes:
> >> That's why they put pilots in water-filled "g-suits"--to eliminate the
> effects of "g". <<
> 
> Not to nit pick, but when I was flying jets for the USAF, we weren't using
> "water-filled" g suits. The are air-filled suits. And these jets I speak of,
> though only trainers, have the highest onset of g's of any aircraft flown 
> today.
> Not that this matters, since I've been in F-16's as well, and it's still
> air-filled, not water-filled. The bladders, located in the legs, inflate with 
> air
> during the onset of g loading, constricting bloodflow to the lower 
> extremeties.
> Of course, you still need some serious leg strength in order to fly these
> suckers. Even with the g suit, you need to be able to constrict your leg 
> muscles
> like there's no tomorrow. If not, you blackout as blood rushes away from your
> brain, and into your feet.
> 
> Oddly enough, there were experiments back in the early 1940s with
> water-filled g suits. However the cumbersome water-filled suits couldn't 
> match the
> performance of suits with air-filled bladders. The problem was that it was 
> believed
> venous return was the major problem of withstanding g loading. It turned out
> that it was arterial pressure. So, the hypertensive effect brought on by
> air-bladder inflation, which works to counter blackout, resulted in the 
> simplified
> air-bladder suit used from WWII to the present.
> 
> Kris
> http://hometown.aol.com/saurierlagen/Paleo-Photography.html

-- 
Roger S. Seymour
Environmental Biology (Darling Building D418)
School of Earth and Environmental Sciences
University of Adelaide
Adelaide, SA 5005, Australia
Phone:  61-8-8303-5596
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email:  roger.seymour@adelaide.edu.au