Cadence and muscle mass

Dan wrote:

> his own internal losses of 75 watts. The internal losses are
primarily due
> to friction inside the body.

No. If you were losing 75 watts due to internal friction, walking would
feel like slogging through water or pedalling a rusty bike. The heat
production is due overwhelmingly to chemical processes. Have you ever
tried to power a 75 watt light bulb via a bicycle generator? Move your
arm back and forth, or move it with the other arm, you will see they
move freely.


> I don't recall seeing many good
> cyclists with huge football legs.


Anton Tkac

among many others. But with today's drug testing, we may never see his
like again..

"41" <[email protected]> wrote in message news:<[email protected]>...
> Dan wrote:
>
> > his own internal losses of 75 watts. The internal losses are
> primarily due
> > to friction inside the body.
>
> No.
<cut>
Abolutely No.

Glucose catabolism reckons to be about 38% efficient at best (under
optimal, aerobic conditions) see:

http://www.rwc.uc.edu/koehler/biophys/8e.html

for a good statement of how this is arrived at. This sets a maximal
biochemical effieciency of 38%. The reality is much less as this is
only half the story.

The ATP produced in glucose catabolism is then used to drive muscle
contraction which is again much less than 100% efficient, as any
chemical process must be. I can't quote any figures for this and
would be interested if anyone can point me to a useful source.

The mechanical losses in the system (body) are just about
insignificant by comparison.

>
> Anton Tkac
>
> among many others. But with today's drug testing, we may never see his
> like again..

Andrew Webster

"Dan" <[email protected]> wrote in message
news:[email protected]...
>I was thumbing through "Biomechanics and Motor Control of Human
>Movement" by
> David A. Winter. In this book there is a part where they discuss
> bicycle
> ergonometry. The author refers to a study by Abbot, Bigland & Ritchie
> (1952)
> in which they linked two cyclists on trainers. The first cyclist
> pedaled in
> a forward motion with his cranks linked by a chain to a second cyclist
> (facing the other way) who resisted in a back-pedaling motion. They
> measured
> the work done by each cyclist and the work transmitted through the
> chain.
> They found that the first cyclist was burning an average of 300 watts,
> the
> chain was transmitting 225 watts and the resisting cyclist was burning
> 150
> watts - half that of the first cyclist. The discussion is about
> internal as
> opposed to external work or power. They say that the first cyclist
> must
> overcome the internal losses of both cyclists.
>
> The back pedaling cyclist is dissipating the 225 watts coming through
> the
> chain by using 150 watts of muscular effort and 75 watts of internal
> losses.
> The forward peddler has to supply the 225 watts to the chain plus
> overcome
> his own internal losses of 75 watts. The internal losses are primarily
> due
> to friction inside the body.
>
> This brought to mind the TDF where it seems that LA by keeping a high
> cadence managed to beat JU who used a lower cadence. The large muscles
> required for a big guy to crank along at a low cadence seem to be less
> efficient than a small guy using less muscular force in a higher
> cadence.
> Picture a completely relaxed Arnold Schwarzenegger lying on a table
> and
> taking one of his feet and moving it through a cycling motion - hard
> work
> flexing all those big muscles. Then do the same with Jennifer Garner,
> this
> would be way more fun and much easier. I don't recall seeing many good
> cyclists with huge football legs.

It comes down to sustainable power to drag and power to weight ratios
where a leaner build is generally better.

>
> There must also be an upper limit on cadence where the high speed
> causes
> viscous or fluid friction losses to counter balance any gain from low
> muscle
> effort.
>
> Any thoughts?

Its more complicted. Increased leg mass requires more energy.....

http://www.ncbi.nlm.nih.gov/entrez/...ubmed&dopt=Abstract&list_uids=8789570Increase in cadence is not quite so simple ..........http://www.ncbi.nlm.nih.gov/entrez/...db=pubmed&dopt=Abstract&list_uids=8775571Phil Holman

On 11 Mar 2005 22:46:25 -0800, "41" <[email protected]>
wrote:

>Dan wrote:
>
>> his own internal losses of 75 watts. The internal losses are
>primarily due
>> to friction inside the body.
>
>No. If you were losing 75 watts due to internal friction, walking would
>feel like slogging through water or pedalling a rusty bike. The heat
>production is due overwhelmingly to chemical processes. Have you ever
>tried to power a 75 watt light bulb via a bicycle generator? Move your
>arm back and forth, or move it with the other arm, you will see they
>move freely.
>
>
>> I don't recall seeing many good
>> cyclists with huge football legs.
>
>
>Anton Tkac
>
>among many others. But with today's drug testing, we may never see his
>like again..

Dear 41,

Actually, there is some heat generated--how could it be
otherwise? Bees deliberately heat up their hives by wing
buzzing.

But much of the 75 watt loss is due to, well, dead weight.

Clip the feet of a dead rider (obtained either as road kill
or from a friendly local mortuary) onto the pedals of this
contraption, and you'll have to keep accelerating everything
from the deceased's hip joints down in a constant, awkward
motion that takes a lot of effort--it's not the same as a
pair of lead weights going in nice circle around the crank.

Thrashing three-hinge flesh-and-bone connecting rods takes
effort. We're just so used to it that we don't realize it,
any more than we notice how much horsepower is needed to
leave the parking space until the engine dies and we have to
push the car out by hand.

Carl Fogel

[email protected] (Andrew Webster) writes:

> "41" <[email protected]> wrote in message news:<[email protected]>...
>> Dan wrote:
>>
>> > his own internal losses of 75 watts. The internal losses are
>> primarily due
>> > to friction inside the body.
>>
>> No.
> <cut>
> Abolutely No.
>
> Glucose catabolism reckons to be about 38% efficient at best (under
> optimal, aerobic conditions) see:
>
> http://www.rwc.uc.edu/koehler/biophys/8e.html
>
> for a good statement of how this is arrived at. This sets a maximal
> biochemical effieciency of 38%. The reality is much less as this is
> only half the story.
>
> The ATP produced in glucose catabolism is then used to drive muscle
> contraction which is again much less than 100% efficient, as any
> chemical process must be. I can't quote any figures for this and
> would be interested if anyone can point me to a useful source.

I think sorting out the various chemical and mechanical efficiencies
of muscle is still an area of active research. These folks here:

http://www.biophysj.org/cgi/content/abstract/79/2/945

Looked at the efficiency of converting ATP to mechanical work in
single muscle fibers and got values varying between about 20-40
percent. A single muscle fiber, while small, still has lots of
mechanical elements to it.

These guys here:

http://jeb.biologists.org/cgi/content/abstract/204/23/4125

looked at the overall efficiency of muscle from glucose or ffa and got
an efficiency of 14-16 percent (this includes the number you mention
above.)

I don't think anyone has been able to measure the chemo-mechanical
transduction efficiency of isolated myosin-actin complexes, but I may
be wrong.

P.S. don't worry that some studies use insect muscle. Insect and
human muscle were created to have only minor differances.

"Philip Holman" <[email protected]> wrote in message
news:[email protected]...
>
> "Dan" <[email protected]> wrote in message
> news:[email protected]...
>>I was thumbing through "Biomechanics and Motor Control of Human
>>Movement" by
>> David A. Winter. In this book there is a part where they discuss
>> bicycle
>> ergonometry. The author refers to a study by Abbot, Bigland & Ritchie
>> (1952)
>> in which they linked two cyclists on trainers. The first cyclist
>> pedaled in
>> a forward motion with his cranks linked by a chain to a second
>> cyclist
>> (facing the other way) who resisted in a back-pedaling motion. They
>> measured
>> the work done by each cyclist and the work transmitted through the
>> chain.
>> They found that the first cyclist was burning an average of 300
>> watts, the
>> chain was transmitting 225 watts and the resisting cyclist was
>> burning 150
>> watts - half that of the first cyclist. The discussion is about
>> internal as
>> opposed to external work or power. They say that the first cyclist
>> must
>> overcome the internal losses of both cyclists.
>>
>> The back pedaling cyclist is dissipating the 225 watts coming through
>> the
>> chain by using 150 watts of muscular effort and 75 watts of internal
>> losses.
>> The forward peddler has to supply the 225 watts to the chain plus
>> overcome
>> his own internal losses of 75 watts. The internal losses are
>> primarily due
>> to friction inside the body.
>>
>> This brought to mind the TDF where it seems that LA by keeping a high
>> cadence managed to beat JU who used a lower cadence. The large
>> muscles
>> required for a big guy to crank along at a low cadence seem to be
>> less
>> efficient than a small guy using less muscular force in a higher
>> cadence.
>> Picture a completely relaxed Arnold Schwarzenegger lying on a table
>> and
>> taking one of his feet and moving it through a cycling motion - hard
>> work
>> flexing all those big muscles. Then do the same with Jennifer Garner,
>> this
>> would be way more fun and much easier. I don't recall seeing many
>> good
>> cyclists with huge football legs.
>
> It comes down to sustainable power to drag and power to weight ratios
> where a leaner build is generally better.
>
>>
>> There must also be an upper limit on cadence where the high speed
>> causes
>> viscous or fluid friction losses to counter balance any gain from low
>> muscle
>> effort.
>>
>> Any thoughts?

I'll try this post again; the urls were hosed.

It's more complicted. Increased leg mass requires more energy.....

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8789570

Increase in cadence is not quite so simple ..........

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8775571

Phil Holman

"41" <[email protected]> wrote in message
news:[email protected]...
> Dan wrote:
>
> > his own internal losses of 75 watts. The internal losses are
> primarily due
> > to friction inside the body.
>
> No. If you were losing 75 watts due to internal friction, walking would
> feel like slogging through water or pedalling a rusty bike. The heat
> production is due overwhelmingly to chemical processes. Have you ever
> tried to power a 75 watt light bulb via a bicycle generator? Move your
> arm back and forth, or move it with the other arm, you will see they
> move freely.

I am no expert (I doubt any of you will argue with me on that) but I am sure
that you are right in that there are losses in chemical processes. The
article that I referred to makes the point that if there were no internal
losses, walking or even running on a level course would be a coast. Running
and cycling certainly heats me up but I can't tell you how much of that heat
comes from friction and how much from inefficient chemical reactions.

Could the frictional losses be different in a tense muscle as opposed to a
relaxed one?

>
>
> > I don't recall seeing many good
> > cyclists with huge football legs.
>
>
> Anton Tkac
>
> among many others. But with today's drug testing, we may never see his
> like again..
>

"Philip Holman" <[email protected]> wrote in message
news:[email protected]...
>
> "Dan" <[email protected]> wrote in message
> news:[email protected]...
> >I was thumbing through "Biomechanics and Motor Control of Human
> >Movement" by
> > David A. Winter. In this book there is a part where they discuss
> > bicycle
> > ergonometry. The author refers to a study by Abbot, Bigland & Ritchie
> > (1952)
> > in which they linked two cyclists on trainers. The first cyclist
> > pedaled in
> > a forward motion with his cranks linked by a chain to a second cyclist
> > (facing the other way) who resisted in a back-pedaling motion. They
> > measured
> > the work done by each cyclist and the work transmitted through the
> > chain.
> > They found that the first cyclist was burning an average of 300 watts,
> > the
> > chain was transmitting 225 watts and the resisting cyclist was burning
> > 150
> > watts - half that of the first cyclist. The discussion is about
> > internal as
> > opposed to external work or power. They say that the first cyclist
> > must
> > overcome the internal losses of both cyclists.
> >
> > The back pedaling cyclist is dissipating the 225 watts coming through
> > the
> > chain by using 150 watts of muscular effort and 75 watts of internal
> > losses.
> > The forward peddler has to supply the 225 watts to the chain plus
> > overcome
> > his own internal losses of 75 watts. The internal losses are primarily
> > due
> > to friction inside the body.
> >
> > This brought to mind the TDF where it seems that LA by keeping a high
> > cadence managed to beat JU who used a lower cadence. The large muscles
> > required for a big guy to crank along at a low cadence seem to be less
> > efficient than a small guy using less muscular force in a higher
> > cadence.
> > Picture a completely relaxed Arnold Schwarzenegger lying on a table
> > and
> > taking one of his feet and moving it through a cycling motion - hard
> > work
> > flexing all those big muscles. Then do the same with Jennifer Garner,
> > this
> > would be way more fun and much easier. I don't recall seeing many good
> > cyclists with huge football legs.
>
> It comes down to sustainable power to drag and power to weight ratios
> where a leaner build is generally better.
>
> >
> > There must also be an upper limit on cadence where the high speed
> > causes
> > viscous or fluid friction losses to counter balance any gain from low
> > muscle
> > effort.
> >
> > Any thoughts?
>
> Its more complicted. Increased leg mass requires more energy.....
>
>
http://www.ncbi.nlm.nih.gov/entrez/...ubmed&dopt=Abstract&list_uids=8789570Increase
in cadence is not quite so simple
...........http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubm
ed&dopt=Abstract&list_uids=8775571Phil Holman
>

The study that I cited was a bit dated, though only a few years older than
me. I suppose that I was trying to leap to unfounded conclusions. My
engineering mind likes to ponder matters of cycling efficiency while
cranking along - it seems to be the primary variable. Maybe I am trying to
justify skinny legs.

Dan wrote:

> ...
> Picture a completely relaxed Arnold Schwarzenegger lying on a table
> and taking one of his feet and moving it through a cycling motion...

No thanks.

> ...Then do the same with Jennifer Garner, this would be way more fun and much easier...

Agreed, and a much more pleasant mental image, to boot.

--
Tom Sherman – Earth (Illinois)

"Dan" <[email protected]> writes:

> "41" <[email protected]> wrote in message
> news:[email protected]...
>> Dan wrote:
>>
>> > his own internal losses of 75 watts. The internal losses are
>> > primarily due to friction inside the body.
>>
>> No. If you were losing 75 watts due to internal friction, walking
>> would feel like slogging through water or pedalling a rusty
>> bike. The heat production is due overwhelmingly to chemical
>> processes. Have you ever tried to power a 75 watt light bulb via a
>> bicycle generator? Move your arm back and forth, or move it with
>> the other arm, you will see they move freely.
>
> I am no expert (I doubt any of you will argue with me on that) but I
> am sure that you are right in that there are losses in chemical
> processes. The article that I referred to makes the point that if
> there were no internal losses, walking or even running on a level
> course would be a coast. Running and cycling certainly heats me up
> but I can't tell you how much of that heat comes from friction and
> how much from inefficient chemical reactions.

These would be better characterized as metabolic functions rather than
chemical reaction. Also, while some of the "heat" is real, much of it
is illusory. The capillaries in our skin dilate to facilitate cooling
and and our skin feels hot, which is in turn perceived through the
nerve endiungs in our skin. This actually offers some regulatory
feedback on how hard we are exerting ourselves, another type of
proprioception.

http://en.wikipedia.org/wiki/Proprioception

> Could the frictional losses be different in a tense muscle as
> opposed to a relaxed one?

The losses within muscles are not from friction but from hysteresis

http://en.wikipedia.org/wiki/Hysteresis

and also from antagonism- muscles pulling against each other across a
joint. Muscles operate by contraction, and almost all skeletal
muscles are arranged in opposing pairs. When one muscle (the agonist)
contracts to move a joint, it must stretch the opposing muscle (the
antagonist)- if the antagonist is tensed, the agonist has to work
harder. Ever try to straighten your leg out when you have a charley
horse in the hamstring? The muscle spasm causing the cramp is very
hard, sometimes impossible, to overcome with the opposing muscles of
the quadriceps.

http://en.wikipedia.org/wiki/Muscles

There is some friction in joints, but healthy joints are very very low
friction structures, between the cartilege and the synovial fluid.

http://en.wikipedia.org/wiki/Joints

Tim McNamara <[email protected]> writes:

> "Dan" <[email protected]> writes:
>
>> "41" <[email protected]> wrote in message
>> news:[email protected]...
>>> Dan wrote:
>>>
>>> > his own internal losses of 75 watts. The internal losses are
>>> > primarily due to friction inside the body.
>>>
>>> No. If you were losing 75 watts due to internal friction, walking
>>> would feel like slogging through water or pedalling a rusty
>>> bike. The heat production is due overwhelmingly to chemical
>>> processes. Have you ever tried to power a 75 watt light bulb via a
>>> bicycle generator? Move your arm back and forth, or move it with
>>> the other arm, you will see they move freely.
>>
>> I am no expert (I doubt any of you will argue with me on that) but I
>> am sure that you are right in that there are losses in chemical
>> processes. The article that I referred to makes the point that if
>> there were no internal losses, walking or even running on a level
>> course would be a coast. Running and cycling certainly heats me up
>> but I can't tell you how much of that heat comes from friction and
>> how much from inefficient chemical reactions.
>
> These would be better characterized as metabolic functions rather than
> chemical reaction. Also, while some of the "heat" is real, much of it
> is illusory. The capillaries in our skin dilate to facilitate cooling
> and and our skin feels hot, which is in turn perceived through the
> nerve endiungs in our skin. This actually offers some regulatory
> feedback on how hard we are exerting ourselves...
[snip]

Whether one calls them "metabolic functions" or "chemical reactions"
they are the same thing. The heat released by converting a pound of
sugar to CO2 and water is the same regardless if it happens in your
body or if you light it with a match.

Malignant hyperthermia is a complication of general anesthesia in
which the metabolic processes in the muscles proceed uncontrolled. It
provides a nice illustration that the "heat" is "real." These folks
get quite hot.

http://en.wikipedia.org/wiki/Malignant_hyperthermia

Shivering generates heat too, which makes it a nice thing to do when
you are cold.

On Sat, 12 Mar 2005 21:56:38 -0600, Jim Smith
<[email protected]> wrote:

[snip]

>Shivering generates heat too, which makes it a nice thing to do when
>you are cold.

Dear Jim,

I don't know if birds or educated fleas do it, but bees do
it:

http://www.bumblebee.org/body.htm

The neat trick is that they somehow uncouple the muscles
from their wings for shivering, somewhat like an escape
artist dislocating his shoulder to take off his jacket.

Of course, we don't even have to shiver to produce
heat--just get half a dozen fellows to sit around a poker
table in a basement for a few hours and see what half a ton
of warm-blooded meat that mysteriously maintains a
hundred-degree internal temperature does to the thermostat.

Carl Fogel

On Fri, 11 Mar 2005 13:42:53 -0800, "Dan"
<[email protected]> wrote:

>I was thumbing through "Biomechanics and Motor Control of Human Movement" by
>David A. Winter. In this book there is a part where they discuss bicycle
>ergonometry. The author refers to a study by Abbot, Bigland & Ritchie (1952)
>in which they linked two cyclists on trainers. The first cyclist pedaled in
>a forward motion with his cranks linked by a chain to a second cyclist
>(facing the other way) who resisted in a back-pedaling motion. They measured
>the work done by each cyclist and the work transmitted through the chain.
>They found that the first cyclist was burning an average of 300 watts, the
>chain was transmitting 225 watts and the resisting cyclist was burning 150
>watts - half that of the first cyclist. The discussion is about internal as
>opposed to external work or power. They say that the first cyclist must
>overcome the internal losses of both cyclists.
>
>The back pedaling cyclist is dissipating the 225 watts coming through the
>chain by using 150 watts of muscular effort and 75 watts of internal losses.
>The forward peddler has to supply the 225 watts to the chain plus overcome
>his own internal losses of 75 watts. The internal losses are primarily due
>to friction inside the body.
>
>This brought to mind the TDF where it seems that LA by keeping a high
>cadence managed to beat JU who used a lower cadence. The large muscles
>required for a big guy to crank along at a low cadence seem to be less
>efficient than a small guy using less muscular force in a higher cadence.
>Picture a completely relaxed Arnold Schwarzenegger lying on a table and
>taking one of his feet and moving it through a cycling motion - hard work
>flexing all those big muscles. Then do the same with Jennifer Garner, this
>would be way more fun and much easier. I don't recall seeing many good
>cyclists with huge football legs.
>
>There must also be an upper limit on cadence where the high speed causes
>viscous or fluid friction losses to counter balance any gain from low muscle
>effort.
>
>Any thoughts?

Dear Dan,

Below is a summary of a long-ago "Ring of Truth" program
that addressed part of your question in terms of jelly
doughnuts and the Tour de France. (It turns out that Homer
Simpson is training for the Tour.)

Basically, most of our output is wasted in the form of heat.

The internal mechanical friction that you have in mind is
probably present, but not really a limiting factor.

Accelerating bigger masses rapidly is simply much
harder--think of the wing beat rate of a hummingbird versus
a vulture, or the heartbeat of an elephant versus a shrew.

Similarly, rapidly bending and straightening heavy limbs
takes more effort. Strap a two-pound exercise weight on each
knee and you'll feel the difference.

Carl Fogel

[begin summary]

The Tour de France--In terms of jelly donuts

Like jelly donuts? How about 30 a day? Well, that's the
number of donuts you would have to eat to get enough
calories to compete for just "one day" during the Tour de
France.

Traveling approximately 2000 miles in 23 days, a Tour de
France cyclist like Lance Armstrong typically eats the
equivalent of 30-32 jelly donuts per day in calories,
according to physicist Philip Morrison of MIT. Morrison
conducted an investigation of the Tour de France for his
1987 PBS documentary series "The Ring of Truth." (In
comparison, a normal adult male eats the equivalent of 12
jelly donuts a day, assuming that each jelly donut is about
250 calories.)

So where do all those donuts go? During a typical day's
race, Morrison says, a biker burns off about 1 or 2 jelly
donuts worth of energy in overcoming friction and
manipulating his bike. Propelling the bike forward in a
typical day's race requires only about 6 jelly donuts of
energy.

Where do the remaining 25 donuts of energy get spent? You
guessed right--it's wasted--in the form of heat. Now, the
human body is a relatively efficient machine. But like all
machines, it unavoidably generates heat which cannot be
employed to perform useful work. This heat--20-25 donuts'
worth, according to Morrison--is mainly carried away in the
form of sweat created by exertion.

Competitors drink about 4 gallons of water a day, and this
water evaporates from their bodies to carry away the heat.
What keeps them cool enough to endure the race, says
Morrison, is the streaming wind that hits their face.

[end summary]

http://www.eurekalert.org/pub_releases/1999-07/AIoP-TTdF-220799.php

[email protected] writes:

> I don't know if birds or educated fleas do it, but bees do
> it:
>
> http://www.bumblebee.org/body.htm

Nice. That be cool.

Tim McNamara wrote:
> "Dan" <[email protected]> writes:
>
> > "41" <[email protected]> wrote in message

> >> bike. The heat production is due overwhelmi ngly to chemical
> >> processes. Have you ever tried to power a 75 watt light bulb via a

> These would be better characterized as metabolic functions rather
than
> chemical reaction. Also, while some of the "heat" is real, much of
it
> is illusory.

Resting, about 100 watts is real. This is why skin-to-skin warming in a
sleeping bag is effective for hypothermia victims.

Metabolism is a system of chemical reactions acting to provide the
energy and materials for biological and physiological processes. One
can be more precise and say a system of biochemical reactions, since
they are not what one typically finds in simple test tube systems. But
they are chemical reactions nevertheless.

> The losses within muscles are not from friction but from hysteresis

One finds all sorts of losses, including friction, which occurs
whenever two macroscopic things slide against each other: muscles
against fascia against skin and bone, and, since not all muscle fibres
contract all exactly alike simultaneously, between muscle fibres; etc.
However, these are all completely insignificant, which is why we don't
feel like we're slogging through water or pedalling a rusty chain when
we move. Hysteresis is not insignificant but there is more energy
recovery than most people think, elastic energy being stored in
tendons, ligaments, and even muscles. The amount stored versus the
amount lost due to hysteresis and antagonism is variable, having much
to do with muscle "tone"; sometimes we have a spring in our step, other
times we have to drag ourselves along, one foot in front of the other.
When running or cimbing hills, one also gets to store energy in the
gravitational field.

Dan wrote:
> "41" <[email protected]> wrote in message
> news:[email protected]...
> > Dan wrote:
> >
> > > his own internal losses of 75 watts. The internal losses are
> > primarily due
> > > to friction inside the body.
> >
> > No. If you were losing 75 watts due to internal friction, walking
would
> > feel like slogging through water or pedalling a rusty bike. The
heat
> > production is due overwhelmingly to chemical processes. Have you
ever
> > tried to power a 75 watt light bulb via a bicycle generator? Move
your
> > arm back and forth, or move it with the other arm, you will see
they
> > move freely.
>
> I am no expert (I doubt any of you will argue with me on that) but I
am sure
> that you are right in tha t there are losses in chemical processes.
The
> article that I referred to makes the point that if there were no
internal
> losses, walking or even running on a level course would be a coast.
Running
> and cycling certainly heats me up but I can't tell y ou how much of
that heat
> comes from friction and how much from inefficient chemical reactions.

The author you cite, Winter, is a knowledgeable fellow. Surely
somewhere in that or one of his many other publications, he mentions
that the losses due to friction are entirely insignificant. Essentially
none of your heat comes from friction. You can test this by having
having someone bend your leg or your arm repeatedly, to see if they
heat up any from friction. You will find that all of the new heat comes
from contact with their hand, not at the site of passive muscle
movement.

> Could the frictional losses be different in a tense muscle as opposed
to a
> relaxed one?

Barely, or rather hardly. Friction is a function of the characteristics
of the material interface, and the normal force. The material interface
does not change, but the various normal forces could be increased some
amount by tensing the muscle. However, the coefficients of friction
(the relevant property of the interface) are so miniscule that any such
change in the normal force will still have an insignificant net effect.

One needs a certain "tone" ("tension") in a muscle for it to be able to
effectively store elastic energy. In e.g. running, elastic storage of
energy in muscles, tendons and ligaments is crucial to efficient
motion. Of far less if any importance in bicycling.
g

"41" <[email protected]> writes:

> Metabolism is a system of chemical reactions acting to provide the
> energy and materials for biological and physiological processes. One
> can be more precise and say a system of biochemical reactions, since
> they are not what one typically finds in simple test tube systems. But
> they are chemical reactions nevertheless.

There is a nice chart online which gives an overview of some of the
main pathways. You can zoom in on an area of interest, down to links
to references to specific enzymes.

http://www.expasy.org/cgi-bin/show_thumbnails.pl

They also have one with some cellular processes thrown in:

http://www.expasy.org/cgi-bin/show_thumbnails.pl?2

Sigma has a nice chart available as a pdf which scales nicely up to
wall size:

http://www.sigmaaldrich.com/Area_of...xplorer/Key_Resources/Metabolic_Pathways.html

--
Turtles all the way down.

On Sat, 12 Mar 2005 23:06:43 -0600, Jim Smith
<[email protected]> wrote:

>[email protected] writes:
>
>> I don't know if birds or educated fleas do it, but bees do
>> it:
>>
>> http://www.bumblebee.org/body.htm
>
> Nice. That be cool.
>

Dear Jim,

I've looked for an explanation of the anatomy, but gotten
nowhere.

The "uncoupling" may even be a misunderstanding--the bees
might not be uncoupling their wings from their muscles, but
just uncoupling their large fore wings from their smaller
rear wings and vibrating the smaller wings.

Esch probably explains whatever happens, but his paper is on
a pay per view basis.

Bzzzzzzz!

Carl Fogel

"41" <[email protected]> wrote in message
news:[email protected]...
>
> Dan wrote:
> > "41" <[email protected]> wrote in message
> > news:[email protected]...
> > > Dan wrote:
> > >
> > > > his own internal losses of 75 watts. The internal losses are
> > > primarily due
> > > > to friction inside the body.
> > >
> > > No. If you were losing 75 watts due to internal friction, walking
> would
> > > feel like slogging through water or pedalling a rusty bike. The
> heat
> > > production is due overwhelmingly to chemical processes. Have you
> ever
> > > tried to power a 75 watt light bulb via a bicycle generator? Move
> your
> > > arm back and forth, or move it with the other arm, you will see
> they
> > > move freely.
> >
> > I am no expert (I doubt any of you will argue with me on that) but I
> am sure
> > that you are right in tha t there are losses in chemical processes.
> The
> > article that I referred to makes the point that if there were no
> internal
> > losses, walking or even running on a level course would be a coast.
> Running
> > and cycling certainly heats me up but I can't tell y ou how much of
> that heat
> > comes from friction and how much from inefficient chemical reactions.
>
> The author you cite, Winter, is a knowledgeable fellow. Surely
> somewhere in that or one of his many other publications, he mentions
> that the losses due to friction are entirely insignificant. Essentially
> none of your heat comes from friction. You can test this by having
> having someone bend your leg or your arm repeatedly, to see if they
> heat up any from friction. You will find that all of the new heat comes
> from contact with their hand, not at the site of passive muscle
> movement.
>
> > Could the frictional losses be different in a tense muscle as opposed
> to a
> > relaxed one?
>
> Barely, or rather hardly. Friction is a function of the characteristics
> of the material interface, and the normal force. The material interface
> does not change, but the various normal forces could be increased some
> amount by tensing the muscle. However, the coefficients of friction
> (the relevant property of the interface) are so miniscule that any such
> change in the normal force will still have an insignificant net effect.
>
> One needs a certain "tone" ("tension") in a muscle for it to be able to
> effectively store elastic energy. In e.g. running, elastic storage of
> energy in muscles, tendons and ligaments is crucial to efficient
> motion. Of far less if any importance in bicycling.
> g
>

OK, I did a little bit of homework - I read farther along in the book. The
author is discussing mechanical work and energy only. He notes that there
are metabolic losses but the book isn't about metabolics, it's about
ergonomics. metabolic loss isn't actually work.

He breaks down the total work into internal and external. External makes the
bike go, internal is lost. He breaks the internal energy loss into four
types.

* Cocontractions - muscles at the same joint working against each other. He
points out that if more than one muscle works at a joint, they end up
working to some degree against each other.
* Isometric contractions against gravity - even coasting on a bike requires
some work just to keep the sack of bones and gristle in position.
* Generation of energy at one joint and absorption at another - similar to
cocontractions but two body segments working against each other.
* Jerky movements - I did a lot of this in high school - I still have
nightmares about my actions at dances. We have all seen new riders who are
working way too hard because they do not move smoothly on the bike.
I suppose a very good and efficient rider has learned to minimize all of the
above. The pulling rider in the experiment was generating 300 watts, 75 or
25% of which wasn't helping him win the race. If he can learn to cut that
25% by even a few percent, he may have the winning margin. This is where I
started with this in comparing LA and JU - maybe LA is more efficient.