From: pjswan@engin.umich.edu (Peter Swanson)
Subject: Re: Unusual strength, IS:Mother Lifts Car Off Child. Uh huh.
Date: Sat, 09 Jan 93 02:24:04 EST
Organization: University of Michigan Engineering, Ann Arbor

In article <28265@dog.ee.lbl.gov> TWChan@lbl.gov (Terry Chan) writes:
>RE my one of my posts on a mother lifting a car off a child:
>
>sngoetze@cip.informatik.uni-erlangen.de (Sebastian Goetze) writes:
>  +The story (told about 3 years ago) went something like this:
> 
>   [Details deleted] 
>  
>  +This seems quite reasonable to me, since I recall from my Physiology
>  +classes, that we usually only use about a sixth of our muscle
>  +strength. Additional sixth are added if we are under stress, *really*
>  +want to, ... are in danger of life. The bones in your leg can carry
>  +about 2 tons, so there's no real limit here. Since her adrenalin level
>  +was probably raised way above normal (child in danger, her expecting
>  +one...) she could probably do it.
>
>Well, I think this is the sort of idea faint recollection that
>gives the story some credibility.  Your leg bones can hold
>2 tons?  What about the rest of you (e.g., joints, tendons,
>ligaments, bladder, etc.)?
>  

I heard a similar story about the Hulk, either Lou Ferrigno
or Hulk Hogan: he saw the parking brake slip on a (medium size)
car while his 2 year old son was playing in the driveway behind it.
Rather than grabbing the kid and letting the car roll into the street
like any rational person, he ran behind the moving car and stopped it
with muscle power alone.  He ended up in the hospital with a severely
strained back and torn ligaments.

The limiting factor (in my experience of lifting very heavy things)
is what you are using to hold on to the car with, not your legs and
back.

At the point where your knees lock, your legs achieve infinite mechanical
advantage.  Nothing short of bone-crushing weight can make you bend your
knees, and your bones are structurally strongest along their long axis.
As long as you don't bend your knees too much, your legs can lift
astounding weights.  I've heard that this is how black belts break
bricks rather than their hands and feet.  This is also how vise-grip
pliers work: if you keep your legs nearly straight, you can get a lot
of leverage with very little effort.

Your back is strongest when you keep it straight, since it is then
under compression and minimal stress is put on the muscles and ligaments.
I've never lifted anything so heavy that it strained my back, when
I kept it straight.

My limits have always been in my arms and hands.  Unless you use your
shoulders, you can only lift as much as you can grip.  My grip is
about 220 pounds per hand.  I once moved a 800 pound wooden rowboat
with my father which we had to lift with our fingertips, and I felt it
in my forearms for a week but there was no serious damage.  Bear in mind
that this is using techiques that minimize strain, rather than
exercising the muscle which is the goal of weightlifting.  (There's
no way I could do 400 pound arm curls!)

I don't think it would be a problem to lift the rear axle of a compact
car (say, under 2,000 pounds) until the wheels were off the ground.
A 70's vintage 4,000 pound Motown Behemoth would be out of the question.
The biggest problem for me is getting a good handhold without squatting
too far.  Keep in mind that the vast majority of the weight of a car
is in the front, and that the weight shifts to the other wheels as you
lift it.

That is, unless you're the macho type that lifts things
with your bladder.

Pete "former property mangler^H^H^H^Hager" Swanson
-- 
| Peter J. Swanson                   |  pjswan@caen.engin.umich.edu        |
| PhD Pre-Candidate                  |  controls specialist                |
| Electrical Engineering:Systems     | Fortunately, ah keep muh feathuhs   |
| University of Michigan             | numbahd for just such ahn emergency.|
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