Physical principles of swimming



K

Kugar

Guest
I wish if someone could scientifically outline as to how do humans swim. Ultimately human body is
heavier than water so it cannot float but on the other hand if constant muscle action is needed to
float ( I am not talking about propulsion to swim from one point to the other) then the swimmer
should get tired pretty quick. I see people almost effortlessly and endlessly floating, makes me
wonder, how does it become possible to defy the rules of physics?

Any help would be greatly appreciated.

Matt
 
"Kugar" <Net*man*@yahoo.com> wrote in message news:[email protected]...
> I wish if someone could scientifically outline as to how do humans swim. Ultimately human body is
> heavier than water so it cannot float but on the other hand if constant muscle action is needed to
> float ( I am not talking about propulsion to swim from one point to the other) then the swimmer
> should get tired pretty quick. I see people almost effortlessly and endlessly floating, makes me
> wonder, how does it become possible to defy the rules of physics?
>
> Any help would be greatly appreciated.
>
> Matt

Human fat is lighter than water, so a person with any fat on them (which is most of us, in varying
degrees) will have a built in partial floating device. The other one is air in the lungs. A live
person always has certain amount of air in their lungs, which aids in floating. Only a cadaver with
no gases in lungs and less fat than what will offset the lean body-mass will sink. There are other
parts of humans that are also lighter than water, I'd have to read up to know which ones in
particular. It's been several years since I read the details.

So, a live human (fat and the air in the lungs) is lighter than the amount of water they displace by
their volume, so therefore, they float.
 
On Wed, 24 Sep 2003 20:53:23 -0700, "DaKitty" <[email protected]> wrote:

* *"Kugar" <Net*man*@yahoo.com> wrote in message *news:[email protected]...
*> I wish if someone could scientifically outline as to how do humans *> swim. Ultimately human body
is heavier than water so it cannot float *> but on the other hand if constant muscle action is
needed to float ( I *> am not talking about propulsion to swim from one point to the other) *> then
the swimmer should get tired pretty quick. I see people almost *> effortlessly and endlessly
floating, makes me wonder, how does it *> become possible to defy the rules of physics? *> *> Any
help would be greatly appreciated. *> *> Matt * *Human fat is lighter than water, so a person with
any fat on them (which is *most of us, in varying degrees) will have a built in partial floating
*device. The other one is air in the lungs. A live person always has certain *amount of air in their
lungs, which aids in floating. Only a cadaver with no *gases in lungs and less fat than what will
offset the lean body-mass will *sink. There are other parts of humans that are also lighter than
water, I'd *have to read up to know which ones in particular. It's been several years *since I read
the details. * *So, a live human (fat and the air in the lungs) is lighter than the amount *of water
they displace by their volume, so therefore, they float. * * * *

Thanks for your reply, you are right about the attributes of fat and air in the lungs but if these
components of human body were enough to keep us afloat then we did not need to learn swimming,
anybody could just jump into water and at least float and not drown. Since it is not so. There is
something that we learn to do other than constant muscle action to be able to float/swim/not drown.

What exactly is the scientific nature of the technique that we acquire?

Any help would be greatly appreciated.

Matt
 
Kugar wrote:
> Thanks for your reply, you are right about the attributes of fat and air in the lungs but if
> these components of human body were enough to keep us afloat then we did not need to learn
> swimming, anybody could just jump into water and at least float and not drown. Since it is not
> so. There is something that we learn to do other than constant muscle action to be able to
> float/swim/not drown.

But it *is* so. Almost every human body has positive buoyancy. However, it is not very much above
neutral, so if the typical person just jumps in the water, he/she will sink quite deep before
returning slowly to the surface. The time required is long enough that if the person doesn't know
he/she will resurface automatically, they will start to panic and flail about wildly until they
drown from exhaustion.

But swimming and floating are not the same thing. You can float without swimming, and you can swim
without floating.

> What exactly is the scientific nature of the technique that we acquire?

Newton's third law: "For every action, there is an equal and opposite reaction."

martin
 
Kugar wrote:

> I wish if someone could scientifically outline as to how do humans swim. Ultimately human body is
> heavier than water so it cannot float but on the other hand if constant muscle action is needed to
> float ( I am not talking about propulsion to swim from one point to the other) then the swimmer
> should get tired pretty quick. I see people almost effortlessly and endlessly floating, makes me
> wonder, how does it become possible to defy the rules of physics?
>
> Any help would be greatly appreciated.

It looks effortless because most human bodies do float.

martin
 
Kugar left this mess on Thu, 25 Sep 2003 07:18:07 -0500 for The Way to clean up:
>
>
>Thanks for your reply, you are right about the attributes of fat and air in the lungs but if these
>components of human body were enough to keep us afloat then we did not need to learn swimming,
>anybody could just jump into water and at least float and not drown. Since it is not so. There is
>something that we learn to do other than constant muscle action to be able to float/swim/not drown.
>
>What exactly is the scientific nature of the technique that we acquire?
>
>Any help would be greatly appreciated.

This is true, Matt. For any extended period of time, effort must be exerted (unless one is wearing a
flotation device) in order to stay above the water. Since the body is mostly water, a good starting
assumption is the buoyancy of a human is about the same as the buoyancy of water (for want of a
better way to phrase it).

But, many parts of the body, bone as an example, are heavier than water and so will sink. These are
offset nearly perfectly by the air cavities in our bodies: lungs, sinuses, to some degree the
digestive tract, and so on. But it's clearly not enough to float a body (except in very salty, heavy
water). Ergo, some muscle function is needed to compensate.

If you look at nearly any form of survival swimming, it seems to be an attempt to "climb a ladder",
in other words, lift the body out of the water.

This is very accurate. Water provides just enough resistance that these forms of floation work. And
that's your answer.

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003
 
"M.W. Smith" wrote:
> But it *is* so. Almost every human body has positive buoyancy...

...with lungs full of air, one might add.

Chief S.
 
This is starting to get silly.

Averaged over the entire body, human density is slightly less than water. Muscle sinks slightly,
bones sink faster, fat floats, full lungs really float, but the average is around 0.99 g/cc. That's
below 1.00 g/cc, so people float.

(Let's ignore the problem of people with heavy shoes and rocks in their pockets.)

There's some individual variation, but almost everybody will float if their lungs are reasonably
full of air. I've only heard of a handful of extremely lean individuals who didn't, and even then
there was some question of how full their lungs were. Even those few exceptions weren't so terribly
far from buoyant that they couldn't tread water easily.

The real question is how comfortably they can float. Some people ( mostly females with buoyant legs,
I believe) can float motionless on their backs for hours with their noses above water. I'm not one
of those. If I stay completely motionless, my legs actually sink slowly, so I naturally rotate to a
standing position with the top 1 cm of my head above water. If I then lean my head back and paddle
my hands slightly, I can keep my nose above water.

For most people, that's not enough above water to feel comfortable. So they must learn to
tread water.

Ross
 
Technically, Ross, the proper position for an unconscious swimmer is face down in the water,
shoulders slightly above.

You could look it up, if you don't believe me. This is the "rest" position of a human in water.

Ross Bogue left this mess on Thu, 25 Sep 2003 14:43:01 +0000 (UTC) for The Way to clean up:
>
>
>
>This is starting to get silly.
>
>Averaged over the entire body, human density is slightly less than water. Muscle sinks slightly,
>bones sink faster, fat floats, full lungs really float, but the average is around 0.99 g/cc. That's
>below 1.00 g/cc, so people float.
>
>(Let's ignore the problem of people with heavy shoes and rocks in their pockets.)
>
>There's some individual variation, but almost everybody will float if their lungs are reasonably
>full of air. I've only heard of a handful of extremely lean individuals who didn't, and even then
>there was some question of how full their lungs were. Even those few exceptions weren't so terribly
>far from buoyant that they couldn't tread water easily.
>
>The real question is how comfortably they can float. Some people ( mostly females with buoyant
>legs, I believe) can float motionless on their backs for hours with their noses above water. I'm
>not one of those. If I stay completely motionless, my legs actually sink slowly, so I naturally
>rotate to a standing position with the top 1 cm of my head above water. If I then lean my head back
>and paddle my hands slightly, I can keep my nose above water.
>
>For most people, that's not enough above water to feel comfortable. So they must learn to
>tread water.
>
>
>
>Ross
>
>
>

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003
 
"Kugar" <Net*man*@yahoo.com> wrote in message news:[email protected]...
> On Wed, 24 Sep 2003 20:53:23 -0700, "DaKitty" <[email protected]> wrote:
>
> * *"Kugar" <Net*man*@yahoo.com> wrote in message
> *news:[email protected]... *> I wish if someone could scientifically
> outline as to how do humans *> swim. Ultimately human body is heavier than water so it cannot
> float *> but on the other hand if constant muscle action is needed to float ( I *> am not talking
> about propulsion to swim from one point to the other) *> then the swimmer should get tired pretty
> quick. I see people almost *> effortlessly and endlessly floating, makes me wonder, how does it *>
> become possible to defy the rules of physics? *> *> Any help would be greatly appreciated. *> *>
> Matt * *Human fat is lighter than water, so a person with any fat on them (which
is
> *most of us, in varying degrees) will have a built in partial floating *device. The other one is
> air in the lungs. A live person always has
certain
> *amount of air in their lungs, which aids in floating. Only a cadaver with
no
> *gases in lungs and less fat than what will offset the lean body-mass will *sink. There are other
> parts of humans that are also lighter than water,
I'd
> *have to read up to know which ones in particular. It's been several years *since I read the
> details. * *So, a live human (fat and the air in the lungs) is lighter than the
amount
> *of water they displace by their volume, so therefore, they float. * * * *
>
> Thanks for your reply, you are right about the attributes of fat and air in the lungs but if these
> components of human body were enough to keep us afloat then we did not need to learn swimming,
> anybody could just jump into water and at least float and not drown.

Actually, it is so, have you ever seen babues swim, newborn babies tend to react just like most
mammals, you throw them in water, and they will swim. Human babies lose that 'instinct' after first
few months, so if we haven't started swimming by them, we will have to re-learn it later. It is when
we panic and start thrashing around, that we wind up with our herad under water, and inhale water
instrad of air, and drown. Once the lungs fill up with water, most of us lose the buoyancy.

> Since it is not so. There is something that we learn to do other than constant muscle action to be
> able to float/swim/not drown.
>
> What exactly is the scientific nature of the technique that we acquire?

We learn to take it easy, and not disturbe the natural balance thhat lets us float by thrashing
around. That balance is pretty delicate, so unless we go gently, we will get our head under water
for too long, and drown. We learn to not be vertical in the water with out arms above our head much,
because that will cause the head to get under water more often, and when we're thrasing, trying to
grab for thin air to pull us out of the water, we disturbe the floating balance just enough to
drown. We learn to relax in water, and we learn the balance and the body position that will keep our
head above the water.
 
"de Valois" <[email protected]> wrote in message news:[email protected]...
> Technically, Ross, the proper position for an unconscious swimmer is face
down
> in the water, shoulders slightly above.
>
> You could look it up, if you don't believe me. This is the "rest" position
of a
> human in water.

You're describing a "dead man's float"

Ross was talking about the kind of comfortable floating that actually allows a person to breathe.
 
"Chief Squawtendrawpet" <[email protected]> wrote in message news:[email protected]...
> "M.W. Smith" wrote:
> > But it *is* so. Almost every human body has positive buoyancy...
>
> ...with lungs full of air, one might add.
>
> Chief S.

yea, we mentioned that already.
 
"Ross Bogue" <[email protected]> wrote in message news:[email protected]...
>
>
> This is starting to get silly.
>
> Averaged over the entire body, human density is slightly less than water. Muscle sinks slightly,
> bones sink faster, fat floats, full lungs really float, but the average is around 0.99 g/cc.
> That's below 1.00 g/cc, so people float.
>
> (Let's ignore the problem of people with heavy shoes and rocks in their pockets.)
>
> There's some individual variation, but almost everybody will float if their lungs are reasonably
> full of air. I've only heard of a handful of extremely lean individuals who didn't, and even then
> there was some question of how full their lungs were. Even those few exceptions weren't so
> terribly far from buoyant that they couldn't tread water easily.
>
> The real question is how comfortably they can float. Some people ( mostly females with buoyant
> legs, I believe) can float motionless on their backs for hours with their noses above water.

Sounds like me :) One day I'll just turn into an Otter ;)

> I'm not one of those. If I stay completely motionless, my legs actually sink slowly, so I
> naturally rotate to a standing position with the top 1 cm of my head above water. If I then lean
> my head back and paddle my hands slightly, I can keep my nose above water.
>
> For most people, that's not enough above water to feel comfortable. So they must learn to
> tread water.
>
>
>
> Ross

very true!
 
In <[email protected]> de Valois wrote:
> Technically, Ross, the proper position for an unconscious swimmer is face down in the water,
> shoulders slightly above.

Yes, I know about the dead man's float. Point taken. It's a very restful position, and only requires
a little paddling when you want to lift your head to breathe. All the same comments (1% above water,
almost everyone can do it, etc.) apply.

Ross
 
de Valois wrote:

> Kugar left this mess on Thu, 25 Sep 2003 07:18:07 -0500 for The Way to clean up:
>
>>
>>Thanks for your reply, you are right about the attributes of fat and air in the lungs but if
>>these components of human body were enough to keep us afloat then we did not need to learn
>>swimming, anybody could just jump into water and at least float and not drown. Since it is not
>>so. There is something that we learn to do other than constant muscle action to be able to
>>float/swim/not drown.
>>
>>What exactly is the scientific nature of the technique that we acquire?
>>
>>Any help would be greatly appreciated.
>
>
> This is true, Matt. For any extended period of time, effort must be exerted (unless one is wearing
> a flotation device) in order to stay above the water.

It is not true. In my own case, I have nearly neutral buoyancy. If I empty my lungs as completely as
possible, I will slowly sink. Yet I can float for hours with no effort beyond normal breathing.

martin
 
When one inhales the body is actually less dense than the water, allowing a swimmer to float! Also
many people actually float even after exhaling all of their air. This is due to body type or body
composition.

"Kugar" <Net*man*@yahoo.com> wrote in message news:[email protected]...
> I wish if someone could scientifically outline as to how do humans swim. Ultimately human body is
> heavier than water so it cannot float but on the other hand if constant muscle action is needed to
> float ( I am not talking about propulsion to swim from one point to the other) then the swimmer
> should get tired pretty quick. I see people almost effortlessly and endlessly floating, makes me
> wonder, how does it become possible to defy the rules of physics?
>
> Any help would be greatly appreciated.
>
> Matt
 
On Fri, 26 Sep 2003 08:38:36 +0200, "M.W. Smith" *> This is true, Matt. For any extended period of
time, effort must be exerted *> (unless one is wearing a flotation device) in order to stay above
the water. * *It is not true. In my own case, I have nearly neutral buoyancy. If I *empty my lungs
as completely as possible, I will slowly sink. Yet I can *float for hours with no effort beyond
normal breathing. * *martin
____________________

Hi Martin:

Thanks for the response. I want to be able to do exactly what you are saying you can do it. How
should I achieve it?

Please advise.

Thanks

Matt
 
Kugar wrote:

> On Fri, 26 Sep 2003 08:38:36 +0200, "M.W. Smith" *> This is true, Matt. For any extended period of
> time, effort must be exerted *> (unless one is wearing a flotation device) in order to stay above
> the water. * *It is not true. In my own case, I have nearly neutral buoyancy. If I *empty my lungs
> as completely as possible, I will slowly sink. Yet I can *float for hours with no effort beyond
> normal breathing. * *martin
> ____________________
>
> Hi Martin:
>
> Thanks for the response. I want to be able to do exactly what you are saying you can do it. How
> should I achieve it?
>
> Please advise.

I was referring to floating on my back, but for most people, floating on the stomach is easier using
the "dead man's float," so called because it is the position dead bodies are usually found in, in
the water. Suppose you are standing in water up to your chest. Take a breath and hold it and simply
fall forward with your arms outstetched but limp. Relax your body completely and let it ben at the
waist. Your arms and legs hang limp. Your face is in the water, and your neck is
limp. There should be no tension or muscle contraction in your body at all.

You can exhale slowly, as you pass the halfway point of exhaling, *slowly* lift your hands and arms
several inches, and then make a sculling motion with your hands as if you are smoothing off a pile
of sand with each hand (or if you saw the movie "Karate Kid" the sculling motion is like the "Wax
off" motion demonstrated by Pat Morita?). As you make this sculling motion (one circuit), your hands
are pressing down slightly on the water. This downward pressure allows you to raise your head just
enough so that your mouth is above the surface. Then you finish exhaling and inhale your next
breath, and you drop back down into the relaxed, dead man's position. You then just keep repeating
this cycle every time you want to breath. Also, as you scull and lift your head, stick your butt up
a little, ie arch your back a little.

As you get comfortable with this you will begin to see how easy this sculling motion is. Then it is
time to add a little frog kick and continue the sculling permanently. Then you are treading water,
and you can keep your head up and breath normally with very little effort.

Floating on your back is just the opposite of the dead man's float. Again stating in water up to
your chest, take a breath and hold it and lean back, arching your back but other wise realaxing
completely (I emphsize that you must relax completely), letting your arms and legs be limp and sink.
Your neck must be completely relaxed. You must let your head sink back, even to the point that water
might splash over your face. When your body stabilizes in a float, exhale and inhale quickly as you
need to breath. Don't hold your breath very long each time you inhale. Try to breath as normally as
possible and notice how exhaling and inhaling affects your buoyancy.

martin
 
M.W. Smith left this mess on Fri, 26 Sep 2003 08:38:36 +0200 for The Way to clean up:
>
>de Valois wrote:
>
>>Kugar left this mess on Thu, 25 Sep 2003 07:18:07 -0500 for The Way to clean up:
>>
>>>
>>>Thanks for your reply, you are right about the attributes of fat and air in the lungs but if
>>>these components of human body were enough to keep us afloat then we did not need to learn
>>>swimming, anybody could just jump into water and at least float and not drown. Since it is not
>>>so. There is something that we learn to do other than constant muscle action to be able to
>>>float/swim/not drown.
>>>
>>>What exactly is the scientific nature of the technique that we acquire?
>>>
>>>Any help would be greatly appreciated.
>>
>>
>> This is true, Matt. For any extended period of time, effort must be exerted (unless one is
>> wearing a flotation device) in order to stay above the water.
>
>It is not true. In my own case, I have nearly neutral buoyancy. If I empty my lungs as completely
>as possible, I will slowly sink. Yet I can float for hours with no effort beyond normal breathing.
>

Sorry, but don't you exhale when you swim? And that means you're sinking. Now let's add the scenario
the OP put up there: the mechanics of swimming. We're NOT talking about a body at rest (so Ross,
your argument is specious here). We're talking about someone exerting effort to move thru the water.
He is inhaling and exhaling, therefore his buoyancy can fluctuate wildly, including being
momentarily sub-buoyant.

End of argument.

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003
 
"de Valois" <[email protected]> wrote in message news:[email protected]...
> M.W. Smith left this mess on Fri, 26 Sep 2003 08:38:36 +0200 for The Way
to
> clean up:
> >
> >de Valois wrote:
> >
> >>Kugar left this mess on Thu, 25 Sep 2003 07:18:07 -0500 for The Way to
clean up:
> >>
> >>>
> >>>Thanks for your reply, you are right about the attributes of fat and air in the lungs but if
> >>>these components of human body were enough to keep us afloat then we did not need to learn
> >>>swimming, anybody could just jump into water and at least float and not drown. Since it is not
> >>>so. There is something that we learn to do other than constant muscle action to be able to
> >>>float/swim/not drown.
> >>>
> >>>What exactly is the scientific nature of the technique that we acquire?
> >>>
> >>>Any help would be greatly appreciated.
> >>
> >>
> >> This is true, Matt. For any extended period of time, effort must be
exerted
> >> (unless one is wearing a flotation device) in order to stay above the
water.
> >
> >It is not true. In my own case, I have nearly neutral buoyancy. If I empty my lungs as completely
> >as possible, I will slowly sink. Yet I can float for hours with no effort beyond normal
> >breathing.
> >
>
> Sorry, but don't you exhale when you swim? And that means you're sinking.
Now
> let's add the scenario the OP put up there: the mechanics of swimming.
We're NOT
> talking about a body at rest (so Ross, your argument is specious here).
We're
> talking about someone exerting effort to move thru the water. He is
inhaling and
> exhaling, therefore his buoyancy can fluctuate wildly, including being momentarily sub-buoyant.
>
> End of argument.

not sure what your point is?
 
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