Physical principles of swimming



de Valois wrote:
> Sorry, but don't you exhale when you swim? And that means you're sinking.

It doesn't mean I'm sinking, because (1) I don't exhale that completely, and more importantly, (2) I
inhale again before gravity has time to overcome the inertia of my body. Nor did I mean to imply
that I sink like a rock, when my lungs are empty. I sink slowly. Several feet underwater, my speed
would increase as the gases in my body compress, but on the surface, the effect of exhaling while
swimming is negligable.

> 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.

He actually wanted to know how to float. I tried to explain that. In any case, exhaling while
swimming is not going to make someone sink. Buoyancy does not fluctuate violently.

martin
 
On Thu, 25 Sep 2003 14:43:01 +0000 (UTC), Ross Bogue <[email protected]> wrote:
>
>
>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.

I think it was Martin and I that had a rather Lengthy discussion on this topic a while back.
The end result was similar to what you have stated above. Depending on body build adn body
leaness a person will float or sink. The heaviest components in teh body are minerals etc.
The lightest are lungs/Air cavities. FEmales have a tendancy to have fewer minerals and
higher fat percentile. During the last discussion I did a spreadsheet based on some
percentiles I picked up. Although fat makes a bit of difference in overall buoyancy it takes
a considerable amount aka 10lbs or so to make a real noticeable buoyancy change. OTOH
minerals etc make a huge difference. Add a couple of lbs of bone and you sink much quicker
than removing ten lbs of fat.

>
>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.

My particular situation is I float with about 2/3-full lungs. I sink with anything much
less. As in your case my legs go pool bottom right off and my vertical floating position is
with about
1/2-3/4in(1.27-1.905CM). I have a difficult time trying to just float.

~Matt

>
>
>
>Ross
 
> 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.

As mentionned, people float because "average people" are on average (during a full breezing cycle)
less dense than water. But one should mention that water density can change. Salt water is much
denser than drinking water. So it will be easier to float on denser water (not to mention in the
Dead Sea!).

But floating is not swimming.

Interestingly, swimmers tend to have - on average, during a full stroke cycle - more body volume out
of the water that their mere buoyancy would allow.

This means that they are using their precious force to get some of their body volume over the
waterline.

There has been huge discussions to know if this is a waste of energy, of it this is a sound strategy
to go faster. One could reasonnably argue that you could reduce drag by "swimming high", as
recommanded by many coaches, by kicking and through "Miller's torque". But other (like TI) could
argue that every Newton (or Watt) used to press water downward could be better used to press it
backward and produce propulsion. Not seen lots of studies on the subject (for example: correlation
between swimming high (= average % of body volume above water level during the stroke cycle) and
performance).

Any ideas about it?

-- Olivier
 
Hello, I propose the following experiment: go to the pool and allow yourself to sink to the botton,
who here can actually sink to the botton, and stay there, without having to move the arms? Without
having to waste energy? I tried it today, and I couldn't stay in the botton. Conclusion, human body
floats! If I am full of air or not is irrelevant, as I intend to have air-full lungs to as long as I
can live! ;)

Test made with one subject: me! Awaiting further results!

Nelson


MJuric wrote in message news:<[email protected]>...
> On Thu, 25 Sep 2003 14:43:01 +0000 (UTC), Ross Bogue <[email protected]> wrote:
> >
> >
> >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.
>
> I think it was Martin and I that had a rather Lengthy discussion on this topic a while back.
> The end result was similar to what you have stated above. Depending on body build adn body
> leaness a person will float or sink. The heaviest components in teh body are minerals etc.
> The lightest are lungs/Air cavities. FEmales have a tendancy to have fewer minerals and
> higher fat percentile. During the last discussion I did a spreadsheet based on some
> percentiles I picked up. Although fat makes a bit of difference in overall buoyancy it takes
> a considerable amount aka 10lbs or so to make a real noticeable buoyancy change. OTOH
> minerals etc make a huge difference. Add a couple of lbs of bone and you sink much quicker
> than removing ten lbs of fat.
>
> >
> >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.
>
> My particular situation is I float with about 2/3-full lungs. I sink with anything much
> less. As in your case my legs go pool bottom right off and my vertical floating position is
> with about
> 1/2-3/4in(1.27-1.905CM). I have a difficult time trying to just float.
>
>
> ~Matt
>
> >
> >
> >
> >Ross
> >
> >
 
On 30 Sep 2003 16:58:14 -0700, [email protected] (nelson) wrote:

>Hello, I propose the following experiment: go to the pool and allow yourself to sink to the botton,
>who here can actually sink to the botton, and stay there, without having to move the arms? Without
>having to waste energy? I tried it today, and I couldn't stay in the botton. Conclusion, human body
>floats! If I am full of air or not is irrelevant, as I intend to have air-full lungs to as long as
>I can live! ;)
>
> Test made with one subject: me! Awaiting further results!
>
> Nelson

Been done several thousand times. I did this as a game as a child and still do it today.
Many times I have contests with my daughter to see who can stay under water the longest. I
usually win, not only because I can hold my breath longer (Even with a partial lung full)
but because I don't have to waste any energy flailing around to stay under water. I can sit
motionless at the bottom of the pool for extended period of times. I can even walk along
the bottom of the pool. There is no question that most/nearly all human bodies sink. And
before you bring up the loating dead body thing. Most dead bodies sink, if air is not
trapped in the lungs. A true drowning victum (Lungs full of water) lays at the bottom of
whatever body of water until the body begins to decompose. This decomposition process
creates gasses that fill cavities in the body and the body eventually rises to the surface.
This is why you read in the news that divers were looking for a body, not boaters. This is
also why you here in the news that the body was found down river three days later. Not
because it floated down river for three days but because it finally rose to the surface. As
you have demonstrated some bodies are less dense and do float even with expelling air as
much as they can. Note however that air is still left in the lungs, air a drowning victom
would not have. There are many factors as previously stated that dictate a floater vs a
sinker. IMO the number one factor is frame build and bone density. The number two factor is
body fat percentage. Show me a short, stocky, lean male and I lay odds on the fact that he
can sit on the bottom of the pool with a partial lung full of air. OTOH show me a tall,
fat, tiny framed (I.E. slim ankles wrist etc) female with osteoperosis and I'll show you a
someone that won't hit the bottom without rocks in her pockets. A few numbers to help with
the math. Water density is appr
1g/cc I use .9937g/cc for various reasons. Protein I.E. Muscle without water or fat or glycogen etc.
1.34g/cc. Minerals I.E. Bones etc
3.038g/cc and fat .9007 g/CC. The average male lung capacity is 5800. (Females 20-25% less) The
percentile of the body that these make up varies somewhat widely depending on source. I used
73.8% water, 19.4% protein, and 6.8% minerals. Fat will be determined by how fat the person
is. From the above numbers you can set up a spread sheet and mess around with variables to
find out what the body density is. Mine came out fairly close for me. This shows me with a
density of .9832 with full lungs neutral buoyancy around 5050cc lungs or expelling 750CC and
heading to the bottom and staying their with anything less. Of course playing with the
numbers makes for interesting results.

~Matt
>
>
>
>
>
>
>MJuric wrote in message news:<[email protected]>...
>> On Thu, 25 Sep 2003 14:43:01 +0000 (UTC), Ross Bogue <[email protected]> wrote:
>> >
>> >
>> >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.
>>
>> I think it was Martin and I that had a rather Lengthy discussion on this topic a while back.
>> The end result was similar to what you have stated above. Depending on body build adn body
>> leaness a person will float or sink. The heaviest components in teh body are minerals etc.
>> The lightest are lungs/Air cavities. FEmales have a tendancy to have fewer minerals and
>> higher fat percentile. During the last discussion I did a spreadsheet based on some
>> percentiles I picked up. Although fat makes a bit of difference in overall buoyancy it takes
>> a considerable amount aka 10lbs or so to make a real noticeable buoyancy change. OTOH
>> minerals etc make a huge difference. Add a couple of lbs of bone and you sink much quicker
>> than removing ten lbs of fat.
>>
>> >
>> >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.
>>
>> My particular situation is I float with about 2/3-full lungs. I sink with anything much
>> less. As in your case my legs go pool bottom right off and my vertical floating position is
>> with about
>> 1/2-3/4in(1.27-1.905CM). I have a difficult time trying to just float.
>>
>>
>> ~Matt
>>
>> >
>> >
>> >
>> >Ross
>> >
>> >
>
 
The specific gravity of an average human body is as close to 1.0 (that of water) as it makes no
difference. Some people float. Some do not. Either way, in open water, eventually you are going to
find your head and or face in the water and so you need to exert effort to stay on top.

nelson left this mess on 30 Sep 2003 16:58:14 -0700 for The Way to clean up:
>
>Hello, I propose the following experiment: go to the pool and allow yourself to sink to the botton,
>who here can actually sink to the botton, and stay there, without having to move the arms? Without
>having to waste energy? I tried it today, and I couldn't stay in the botton. Conclusion, human body
>floats! If I am full of air or not is irrelevant, as I intend to have air-full lungs to as long as
>I can live! ;)
>
> Test made with one subject: me! Awaiting further results!
>
> Nelson
>
>
>
>
>
>
>MJuric wrote in message news:<[email protected]>...
>> On Thu, 25 Sep 2003 14:43:01 +0000 (UTC), Ross Bogue <[email protected]> wrote:
>> >
>> >
>> >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.
>>
>> I think it was Martin and I that had a rather Lengthy discussion on this topic a while back.
>> The end result was similar to what you have stated above. Depending on body build adn body
>> leaness a person will float or sink. The heaviest components in teh body are minerals etc.
>> The lightest are lungs/Air cavities. FEmales have a tendancy to have fewer minerals and
>> higher fat percentile. During the last discussion I did a spreadsheet based on some
>> percentiles I picked up. Although fat makes a bit of difference in overall buoyancy it takes
>> a considerable amount aka 10lbs or so to make a real noticeable buoyancy change. OTOH
>> minerals etc make a huge difference. Add a couple of lbs of bone and you sink much quicker
>> than removing ten lbs of fat.
>>
>> >
>> >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.
>>
>> My particular situation is I float with about 2/3-full lungs. I sink with anything much
>> less. As in your case my legs go pool bottom right off and my vertical floating position is
>> with about
>> 1/2-3/4in(1.27-1.905CM). I have a difficult time trying to just float.
>>
>>
>> ~Matt
>>
>> >
>> >
>> >
>> >Ross
>> >
>> >
>> >

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003
 
MJuric wrote in message news:<[email protected]>...
> On 30 Sep 2003 16:58:14 -0700, [email protected] (nelson) wrote:
>
> >Hello, I propose the following experiment: go to the pool and allow yourself to sink to the
> >botton, who here can actually sink to the botton, and stay there, without having to move the
> >arms? Without having to waste energy? I tried it today, and I couldn't stay in the botton.
> >Conclusion, human body floats! If I am full of air or not is irrelevant, as I intend to have
> >air-full lungs to as long as I can live! ;)
> >
> > Test made with one subject: me! Awaiting further results!
> >
> > Nelson
>
> Been done several thousand times. I did this as a game as a child and still do it today.
> Many times I have contests with my daughter to see who can stay under water the longest. I
> usually win, not only because I can hold my breath longer (Even with a partial lung full)
> but because I don't have to waste any energy flailing around to stay under water. I can sit
> motionless at the bottom of the pool for extended period of times. I can even walk along the
> bottom of the pool. There is no question that most/nearly all human bodies sink. And before
> you bring up the loating dead body thing. <...>

Nice lesson, thanks! But, I haven't the intention of bring the dead body in it. I want live accounts
as the one you gave above. Does your daughter can walk in the botton too? Can you lie down touching
the botton of the pool? Montionless? Etc... It is also not a context of who can stay longer in the
botton, but just of who can stand, walk, sit, lie, etc.... Completely submersed

Nelson
 
On 1 Oct 2003 11:41:46 -0700, [email protected] (nelson) wrote:

>MJuric wrote in message news:<[email protected]>...
>> On 30 Sep 2003 16:58:14 -0700, [email protected] (nelson) wrote:
>>
>> >Hello, I propose the following experiment: go to the pool and allow yourself to sink to the
>> >botton, who here can actually sink to the botton, and stay there, without having to move the
>> >arms? Without having to waste energy? I tried it today, and I couldn't stay in the botton.
>> >Conclusion, human body floats! If I am full of air or not is irrelevant, as I intend to have
>> >air-full lungs to as long as I can live! ;)
>> >
>> > Test made with one subject: me! Awaiting further results!
>> >
>> > Nelson
>>
>> Been done several thousand times. I did this as a game as a child and still do it today.
>> Many times I have contests with my daughter to see who can stay under water the longest. I
>> usually win, not only because I can hold my breath longer (Even with a partial lung full)
>> but because I don't have to waste any energy flailing around to stay under water. I can sit
>> motionless at the bottom of the pool for extended period of times. I can even walk along the
>> bottom of the pool. There is no question that most/nearly all human bodies sink. And before
>> you bring up the loating dead body thing. <...>
>
>Nice lesson, thanks! But, I haven't the intention of bring the dead body in it. I want live
>accounts as the one you gave above. Does your daughter can walk in the botton too?

No she cannot. She's well ... Abit on the pudgy side and she's a female and a prepubecent<SP> one at
that. I'm figuring the fact that she is younger would give her slightly less dense bone mass (more
cartilage)

> Can you lie down touching the botton of the pool? Montionless? Etc...

Yes. Actually I find it very relaxing to sit at the bottom of a quit pool with my eyes closed
motionless. Almost like a sensory depravation tank if the pool is warm enough.

>It is also not a context of who can stay longer in the botton, but just of who can stand, walk,
>sit, lie, etc.... Completely submersed

The way I stay on the bottom of the pool is by letting out an amount of air. If I were to
completely expell all of my air I would not be able to stay submerged for a very long
period of time. I introduced the time issue as a variable to help with the idea of how much
air I need to expell before I sink. As stated before its probably around 1/3 of my lung
capacity expelled before I sink. This leaves plenty for me to hold my breath for quite a
period of time.

~Matt

>
> Nelson
 
"nelson" <[email protected]> wrote in message
news:[email protected]...
> MJuric wrote in message news:<[email protected]>...
> > On 30 Sep 2003 16:58:14 -0700, [email protected] (nelson) wrote:
> >
> > >Hello, I propose the following experiment: go to the pool and allow yourself to sink to the
> > >botton, who here can actually sink to the botton, and stay there, without having to move the
> > >arms? Without having to waste energy? I tried it today, and I couldn't stay in the botton.
> > >Conclusion, human body floats! If I am full of air or not is irrelevant, as I intend to have
> > >air-full lungs to as long as I can live! ;)
> > >
> > > Test made with one subject: me! Awaiting further results!
> > >
> > > Nelson
> >
> > Been done several thousand times. I did this as a game as a child and still do it today. Many
> > times I have contests with my daughter to see who can stay under water the longest. I usually
> > win, not only because I can hold my breath longer (Even with a partial lung full) but because I
> > don't have to waste any energy flailing around to stay under water. I can sit motionless at the
> > bottom of the pool for extended period of times. I can even walk along the bottom of the pool.
> > There is no question that most/nearly all human bodies sink. And before you bring up the loating
> > dead body thing. <...>
>
> Nice lesson, thanks! But, I haven't the intention of bring the dead body in it. I want live
> accounts as the one you gave above. Does your daughter can walk in the botton too? Can you lie
> down touching the botton of the pool? Montionless? Etc... It is also not a context of who can stay
> longer in the botton, but just of who can stand, walk, sit, lie, etc.... Completely submersed
>
> Nelson

in my case, I float. The fat in my butt and my boobs, and some of it in other places, it's like
wearing a 10mm wetsuit with padding added in strategic places. Bottom of the pool ... I'd need about
20 pounds of lead in my pockets to stay there.
 
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