pulling up is more efficient mechanically



Ken Roberts wrote:
> [email protected] wrote
> > This kind of rubbish has been tested scientifically

>
> Please give me a hint: _What_ stuff has been tested scientifically?
>
> I might agree with you if I only knew what you were specifically talking
> about.
>
> Ken


This upward pulling rubbish of course.
Almost all the force of pedalling comes from downward pressure.
 
K

Ken Roberts

Guest
<[email protected]> wrote
> This upward pulling rubbish of course.


Well "lightening" or "unweighting" the upstroke might possibly be "rubbish"
by some standand. If so, then my point in this thread is that it's
mechanically more efficient rubbish.

> Almost all the force of pedalling comes from downward pressure.


In earlier posts on this thread, the numerical example I gave had 83% of
total work from downward pressure and 17% from upward lifting.

Sounds like 83% is not close enough to "Almost all" for you. So what do you
think is the "correct" percentage? (is it the same for all cyclists? casual
riders? pro racers?). And what's the _evidence_ for this more correct
percentage?

Ken
 
T

Tim McNamara

Guest
In article <X%[email protected]>,
"Ken Roberts" <[email protected]> wrote:

> <[email protected]> wrote
> > This upward pulling rubbish of course.

>
> Well "lightening" or "unweighting" the upstroke might possibly be "rubbish"
> by some standand. If so, then my point in this thread is that it's
> mechanically more efficient rubbish.
>
> > Almost all the force of pedalling comes from downward pressure.

>
> In earlier posts on this thread, the numerical example I gave had 83% of
> total work from downward pressure and 17% from upward lifting.
>
> Sounds like 83% is not close enough to "Almost all" for you. So what do you
> think is the "correct" percentage? (is it the same for all cyclists? casual
> riders? pro racers?). And what's the _evidence_ for this more correct
> percentage?


Buy yourself a copy of the third edition of _Bicycling Science_, by
Wilson with Papadopoulos, which summarizes the available research up to
a couple of years ago. Measured pedal force data on standard crank
(Okajima, 1983) arrangements has found that 100% of the forces moving
the pedals push down- not necessarily straight down but within 20-30
degrees of vertical. The book also includes Okajima's dynamic model of
the leg in cycling which you might find interesting.

Frank Day's PowerCranks, which use a clutch mechanism that forces the
rider to lift the rising leg on its own, are claimed to result in a 20%
increase in power in 7 months and 40% in 9 months. Those are result
claimed by Day, however. I do not know if independent verification has
been done.
 
On Nov 2, 7:42 pm, Tim McNamara <[email protected]> wrote:
> In article <X%[email protected]>,
> "Ken Roberts" <[email protected]> wrote:
>
>
>
>
>
> > <[email protected]> wrote
> > > This upward pulling rubbish of course.

>
> > Well "lightening" or "unweighting" the upstroke might possibly be "rubbish"
> > by some standand. If so, then my point in this thread is that it's
> > mechanically more efficient rubbish.

>
> > > Almost all the force of pedalling comes from downward pressure.

>
> > In earlier posts on this thread, the numerical example I gave had 83% of
> > total work from downward pressure and 17% from upward lifting.

>
> > Sounds like 83% is not close enough to "Almost all" for you. So what do you
> > think is the "correct" percentage? (is it the same for all cyclists? casual
> > riders? pro racers?). And what's the _evidence_ for this more correct
> > percentage?Buy yourself a copy of the third edition of _Bicycling Science_, by

> Wilson with Papadopoulos, which summarizes the available research up to
> a couple of years ago. Measured pedal force data on standard crank
> (Okajima, 1983) arrangements has found that 100% of the forces moving
> the pedals push down- not necessarily straight down but within 20-30
> degrees of vertical. The book also includes Okajima's dynamic model of
> the leg in cycling which you might find interesting.
>
> Frank Day's PowerCranks, which use a clutch mechanism that forces the
> rider to lift the rising leg on its own, are claimed to result in a 20%
> increase in power in 7 months and 40% in 9 months. Those are result
> claimed by Day, however. I do not know if independent verification has
> been done.- Hide quoted text -- Show quoted text -





Of course correct total unweighting or "pulling up" adds nothing to
upstroke pedal power, what it does is upset the balance of feet on
pedals/cranks and the weight of push down leg is added to the press
down power which would mean this force could be 110 % or more of the
downforce if unweighting had not been used. In the case of Powercranks
this added down force would be more as the weight of pedal and part of
crank would be added to the leg weight. So with normal crank use the
end result of total unweighting would be no negative force from rising
leg and increased force from down leg.
 
T

Tim McNamara

Guest
In article <[email protected]>,
[email protected] wrote:

> On Nov 2, 7:42 pm, Tim McNamara <[email protected]> wrote:
> > In article <X%[email protected]>,
> > "Ken Roberts" <[email protected]> wrote:
> >
> > > <[email protected]com> wrote
> > > > This upward pulling rubbish of course.

> >
> > > Well "lightening" or "unweighting" the upstroke might possibly be
> > > "rubbish" by some standand. If so, then my point in this thread
> > > is that it's mechanically more efficient rubbish.

> >
> > > > Almost all the force of pedalling comes from downward pressure.

> >
> > > In earlier posts on this thread, the numerical example I gave had
> > > 83% of total work from downward pressure and 17% from upward
> > > lifting.

> >
> > > Sounds like 83% is not close enough to "Almost all" for you. So
> > > what do you think is the "correct" percentage? (is it the same
> > > for all cyclists? casual riders? pro racers?). And what's the
> > > _evidence_ for this more correct percentage?

> >
> > Buy yourself a copy of the third edition of _Bicycling Science_, by
> > Wilson with Papadopoulos, which summarizes the available research
> > up to a couple of years ago. Measured pedal force data on standard
> > crank (Okajima, 1983) arrangements has found that 100% of the
> > forces moving the pedals push down- not necessarily straight down
> > but within 20-30 degrees of vertical. The book also includes
> > Okajima's dynamic model of the leg in cycling which you might find
> > interesting.
> >
> > Frank Day's PowerCranks, which use a clutch mechanism that forces
> > the rider to lift the rising leg on its own, are claimed to result
> > in a 20% increase in power in 7 months and 40% in 9 months. Those
> > are result claimed by Day, however. I do not know if independent
> > verification has been done.

>
> Of course correct total unweighting or "pulling up" adds nothing to
> upstroke pedal power, what it does is upset the balance of feet on
> pedals/cranks and the weight of push down leg is added to the press
> down power which would mean this force could be 110 % or more of the
> downforce if unweighting had not been used. In the case of
> Powercranks this added down force would be more as the weight of
> pedal and part of crank would be added to the leg weight. So with
> normal crank use the end result of total unweighting would be no
> negative force from rising leg and increased force from down leg.


Please get and use a newsreader so that I don't have to fix the
munged-up formatting to reply to your post. You can get one for free
practically any platform: www.newsreaders.com and it will be a *lot*
faster to use than Google Groups' execrable interface.

You're correct except for there is no *increased* force in the extending
leg in the situation you cite. There is an increased *net force* which
is a distinction worth making. However, Day's claims seem highly
optimistic. Phil Holman cited a study from 2003 that showed a 2%
improvement, IIRC. A bit lower than 20% to 40% and probably useless, a
2% improvement is probably inside the error of measurement.
 
K

Ken Roberts

Guest
Tim McNamara wrote
> Measured pedal force data on standard crank (Okajima, 1983)
> arrangements has found that 100% of the forces moving
> the pedals push down- not necessarily straight down but
> within 20-30 degrees of vertical.


But "pedal force" is not what my mechanical efficiency claim was about. My
claim was about force exerted by the hip flexion (and also some by knee
flexion) muscles on the _leg_, so the muscular force lifted a portion
("lightening", "unweighting") of the weight of the leg, and some force from
the pedal lifts the leg's remaining weight.

So downward force on the pedal during the upstroke is just what I should
expect to be measured, based on my explanation and numerical example.

The net force between pedal and foot in the upstroke is the vector sum of:
(a) weight of the leg; (b) upward lifting of the weight of leg by its own
muscles; (c) resistance or stiffness by the leg's down-push muscles not yet
relaxed from their previous big push. So
.. upstroke pedal force F = - (a) + (b) - (c)

Perhaps (a) the effective weight of the leg on the upstroke pedal can be
reliably estimated in advance of the performance and will remain stable
through the whole upstroke. But it's pretty hard to directly measure (c)
the resistance of the down-push muscles, and it changes during the upstroke.
So if you can measure only F and (a), but not (c), then you don't have a way
to estimate (b).

Therefore I'm surprised that some people are so sure they know that (b) is
small. Still looking forward to the evidence that, "this ... has been
tested scientically".

Ken

P.S. Given the nature of the unmeasurable data component, it's much easier
to use an inequality relationship to show that the Work of force (b) is
_large_ in at least one important study, and that's what I did recently in
the thread on "Coyle Kautz 1991" study.
 
T

Tim McNamara

Guest
In article
<[email protected]>,
"Ken Roberts" <[email protected]> wrote:

> Tim McNamara wrote
> > Measured pedal force data on standard crank (Okajima, 1983)
> > arrangements has found that 100% of the forces moving the pedals
> > push down- not necessarily straight down but within 20-30 degrees
> > of vertical.

>
> But "pedal force" is not what my mechanical efficiency claim was
> about. My claim was about force exerted by the hip flexion (and also
> some by knee flexion) muscles on the _leg_, so the muscular force
> lifted a portion ("lightening", "unweighting") of the weight of the
> leg, and some force from the pedal lifts the leg's remaining weight.
>
> So downward force on the pedal during the upstroke is just what I
> should expect to be measured, based on my explanation and numerical
> example.


Unfortunately your explanations have been sufficiently convoluted that
it's not easy to make out what your point is. It seems to change from
post to post. You initially tried to claim that pulling up is more
efficient than pushing down due to something about the force being
transmitted through the ankle and such. Now you're apparently saying
that lifting the ascending leg results in more net power to the
descending pedal. Well, yup, that'd be true but it's just not something
that happens much- only when you focus on it.

> The net force between pedal and foot in the upstroke is the vector
> sum of: (a) weight of the leg; (b) upward lifting of the weight of
> leg by its own muscles; (c) resistance or stiffness by the leg's
> down-push muscles not yet relaxed from their previous big push. So .
> upstroke pedal force F = - (a) + (b) - (c)


As the descending leg pushes down, the ascending leg is lifted by the
pedal. The upward lift is resisted by the weight of the leg and by the
viscous resistance of the muscles. It's unlikely that there's much by
way of "unrelaxed" muscles resisting the pedal stroke unless you are
having muscle spasms or some sort of neuromuscular malfunction. Muscles
relax pretty fast, especially in trained cyclists.

> Perhaps (a) the effective weight of the leg on the upstroke pedal can
> be reliably estimated in advance of the performance and will remain
> stable through the whole upstroke. But it's pretty hard to directly
> measure (c) the resistance of the down-push muscles, and it changes
> during the upstroke. So if you can measure only F and (a), but not
> (c), then you don't have a way to estimate (b).


Why? You use a strain gauge on the crank and measure the force of the
foot against the pedal. This has been done already, and I have already
cited where you can find the information.

> Therefore I'm surprised that some people are so sure they know that
> (b) is small. Still looking forward to the evidence that, "this ...
> has been tested scientically".


You've been told where you can find the evidence. (b) is vanishingly
small as in nonexistent according to the measurements. The exception
would be the Power Cranks which cannot provide lift to the ascending leg.

> P.S. Given the nature of the unmeasurable data component, it's much
> easier to use an inequality relationship to show that the Work of
> force (b) is _large_ in at least one important study, and that's what
> I did recently in the thread on "Coyle Kautz 1991" study.


What's unmeasureable about it? Strain gauges on the cranks will measure
the force magnitude and direction. Heck I think that you can measure
this at home with an SRM power meter and graph it out on your computer.
 
G

graham

Guest
"Ken Roberts" <[email protected]> wrote in message
news:[email protected]
>Snip<


> The net force between pedal and foot in the upstroke is the vector sum of:
> (a) weight of the leg; (b) upward lifting of the weight of leg by its own
> muscles; (c) resistance or stiffness by the leg's down-push muscles not
> yet relaxed from their previous big push. So
> . upstroke pedal force F = - (a) + (b) - (c)


As we appear to be counting the angels on the head of a pin then what about
the release of the eleastic forces that have built up in all the structures
that have helped to stabilise the body and transfer the force from the large
pushing muscles to the pedal. My view is that at the end of the stroke those
muscles will relax very quickly aided by these elastic forces. Sitting here
I just carried out a little experiment which you might like to repeat. Lift
your heel slightly off the floor and push down as hard as you can on the
ball of your foot then consciously release that effort as quickly as you can
and see what happens to your leg. Also notice all the reactions right up
through your core muscles, ligaments and tendons. There is far more going on
than your simple three term relationship represents.

Graham.
 
P

Peter Cole

Guest
Ken Roberts wrote:
> Tim McNamara wrote
>> Measured pedal force data on standard crank (Okajima, 1983)
>> arrangements has found that 100% of the forces moving
>> the pedals push down- not necessarily straight down but
>> within 20-30 degrees of vertical.

>
> But "pedal force" is not what my mechanical efficiency claim was about. My
> claim was about force exerted by the hip flexion (and also some by knee
> flexion) muscles on the _leg_, so the muscular force lifted a portion
> ("lightening", "unweighting") of the weight of the leg, and some force from
> the pedal lifts the leg's remaining weight.
>
> So downward force on the pedal during the upstroke is just what I should
> expect to be measured, based on my explanation and numerical example.
>
> The net force between pedal and foot in the upstroke is the vector sum of:
> (a) weight of the leg; (b) upward lifting of the weight of leg by its own
> muscles; (c) resistance or stiffness by the leg's down-push muscles not yet
> relaxed from their previous big push. So
> . upstroke pedal force F = - (a) + (b) - (c)
>
> Perhaps (a) the effective weight of the leg on the upstroke pedal can be
> reliably estimated in advance of the performance and will remain stable
> through the whole upstroke. But it's pretty hard to directly measure (c)
> the resistance of the down-push muscles, and it changes during the upstroke.
> So if you can measure only F and (a), but not (c), then you don't have a way
> to estimate (b).
>
> Therefore I'm surprised that some people are so sure they know that (b) is
> small. Still looking forward to the evidence that, "this ... has been
> tested scientically".
>
> Ken
>
> P.S. Given the nature of the unmeasurable data component, it's much easier
> to use an inequality relationship to show that the Work of force (b) is
> _large_ in at least one important study, and that's what I did recently in
> the thread on "Coyle Kautz 1991" study.
>
>


You are neglecting the power required to accelerate the leg mass during
the upstroke.

Check out fig 4 in:
<http://www.me.utexas.edu/~neptune/Papers/essr30(4).pdf>
 
M

Michael Press

Guest
In article <[email protected]>,
"graham" <[email protected]> wrote:

> "Ken Roberts" <[email protected]> wrote in message
> news:[email protected]
> >Snip<

>
> > The net force between pedal and foot in the upstroke is the vector sum of:
> > (a) weight of the leg; (b) upward lifting of the weight of leg by its own
> > muscles; (c) resistance or stiffness by the leg's down-push muscles not
> > yet relaxed from their previous big push. So
> > . upstroke pedal force F = - (a) + (b) - (c)

>
> As we appear to be counting the angels on the head of a pin then what about
> the release of the eleastic forces that have built up in all the structures
> that have helped to stabilise the body and transfer the force from the large
> pushing muscles to the pedal. My view is that at the end of the stroke those
> muscles will relax very quickly aided by these elastic forces. Sitting here
> I just carried out a little experiment which you might like to repeat. Lift
> your heel slightly off the floor and push down as hard as you can on the
> ball of your foot then consciously release that effort as quickly as you can
> and see what happens to your leg. Also notice all the reactions right up
> through your core muscles, ligaments and tendons. There is far more going on
> than your simple three term relationship represents.


I notice muscular follow through past the bottom of the
pedal stroke when turning at a high cadence. The
obvious symptom is bouncing in the saddle. Normally I
do not think about lifting my leg on the rising stroke.
At a high cadence I lift my leg to smooth the pedaling
motion. At lower cadence I go back to not thinking
about lifting my leg.

--
Michael Press
 
K

Ken Roberts

Guest
graham wrote
> My view is that at the end of the stroke those muscles will relax very
> quickly aided by these elastic forces.


That was not the conclusion of the Neptune Herzog 1999 study when they
actually made some careful measurements.

> ... notice all the reactions right up through your core muscles, ligaments
> and tendons. There is far more going on than your simple three term
> relationship represents.


Yes you're right. I focused on only enough factors to try to make it clear
why the data proposed by Tim McNamara were not inconsistent with the claim
that lotsa skilled riders do significant "unweighting" or "lightening" of
the upstroke pedal.

> we appear to be counting the angels on the head of a pin


The move of unweighting or lightening the upstroke could contribute 10-20%
of total power to the drivetrain for some riders. And the forces from
unrelaxed down-push muscles, as measured by Neptune + Herzog, were a lot
bigger than "angels".

Ken
 
K

Ken Roberts

Guest
Peter Cole wrote
> You are neglecting the power required to accelerate the leg mass during
> the upstroke.


You're right. I also neglected the kinetic energy from the mass of the lower
leg moving backward thru the bottom of the cycle.

I was trying to focus on the three kinds of force which result in
significant net Work thru the entire upstroke. I think the inertial forces
on the masses of the upper and lower legs net out to roughly zero Work (in
Joules) -- see Figure 2B in the reference below, which shows that Kinetic
Energy is the same the start (180 degrees) and the finish (360 degrees) of
the upstroke, with a peak at around 290 degrees.

> Check out fig 4 in:

http://www.me.utexas.edu/~neptune/Papers/essr30(4).pdf

Yes that figure is very helpful, thanks Peter.

The graph in the lower left in Figure 4 on page 163 is for "the combined
action of all other muscles included in the model (mostly flexors, which
explains why most of their power is produced in the upstroke)". Indeed the
graph shows those muscles producing substantial positive power, with peak
midway through the upstroke.

Several other points in the paper show how complicated the working of
different muscles is during pedaling, and how the relationship between
forces in the muscles and forces at the crank is not only complicated but
non-intuitive.

"Biomechanical Determinants of Pedaling Energetics: Internal and External
Work Are Not Independent". Steven A. Kautz + Richard R. Neptune. Exercise
Sport Science Review, vol. 30, no. 4, pp. 159-165, 2002.
 
P

Phil Holman

Guest
"Tim McNamara" <[email protected]> wrote in message
news:[email protected]
> In article <[email protected]>,
> [email protected] wrote:
>
>> On Nov 2, 7:42 pm, Tim McNamara <[email protected]> wrote:
>> > In article <X%[email protected]>,
>> > "Ken Roberts" <[email protected]> wrote:
>> >
>> > > <[email protected]> wrote
>> > > > This upward pulling rubbish of course.
>> >
>> > > Well "lightening" or "unweighting" the upstroke might possibly be
>> > > "rubbish" by some standand. If so, then my point in this thread
>> > > is that it's mechanically more efficient rubbish.
>> >
>> > > > Almost all the force of pedalling comes from downward pressure.
>> >
>> > > In earlier posts on this thread, the numerical example I gave had
>> > > 83% of total work from downward pressure and 17% from upward
>> > > lifting.
>> >
>> > > Sounds like 83% is not close enough to "Almost all" for you. So
>> > > what do you think is the "correct" percentage? (is it the same
>> > > for all cyclists? casual riders? pro racers?). And what's the
>> > > _evidence_ for this more correct percentage?
>> >
>> > Buy yourself a copy of the third edition of _Bicycling Science_, by
>> > Wilson with Papadopoulos, which summarizes the available research
>> > up to a couple of years ago. Measured pedal force data on standard
>> > crank (Okajima, 1983) arrangements has found that 100% of the
>> > forces moving the pedals push down- not necessarily straight down
>> > but within 20-30 degrees of vertical. The book also includes
>> > Okajima's dynamic model of the leg in cycling which you might find
>> > interesting.
>> >
>> > Frank Day's PowerCranks, which use a clutch mechanism that forces
>> > the rider to lift the rising leg on its own, are claimed to result
>> > in a 20% increase in power in 7 months and 40% in 9 months. Those
>> > are result claimed by Day, however. I do not know if independent
>> > verification has been done.

>>
>> Of course correct total unweighting or "pulling up" adds nothing to
>> upstroke pedal power, what it does is upset the balance of feet on
>> pedals/cranks and the weight of push down leg is added to the press
>> down power which would mean this force could be 110 % or more of the
>> downforce if unweighting had not been used. In the case of
>> Powercranks this added down force would be more as the weight of
>> pedal and part of crank would be added to the leg weight. So with
>> normal crank use the end result of total unweighting would be no
>> negative force from rising leg and increased force from down leg.

>
> Please get and use a newsreader so that I don't have to fix the
> munged-up formatting to reply to your post. You can get one for free
> practically any platform: www.newsreaders.com and it will be a *lot*
> faster to use than Google Groups' execrable interface.
>
> You're correct except for there is no *increased* force in the
> extending
> leg in the situation you cite. There is an increased *net force*
> which
> is a distinction worth making. However, Day's claims seem highly
> optimistic. Phil Holman cited a study from 2003 that showed a 2%
> improvement, IIRC. A bit lower than 20% to 40% and probably useless,
> a
> 2% improvement is probably inside the error of measurement.


Tim, the 2% improvement was in gross efficiency. If a rider improves
their efficiency from say, 20% to 22%, this can result in a power
increase of 2/20*100 = 10%.
The 2% improvement is statistically significant, i.e., the probability
of the 2% being an error or random improvement in the 6 PC subjects
versus the 6 controls is very small. 1 in 924 to be exact.

Phil H
 
K

Ken Roberts

Guest
Tim McNamara wrote
> What's unmeasureable about it? Strain gauges on
> the cranks will measure the force magnitude and direction.


Strain gauges measure the force to the pedal or the crank. They do not
measure the force exerted by the hip-flexion muscles, which is what I and
some other people are talking about in this thread -- and what some
scientific researchers have been working hard to try to estimate by clever
means.

(Unless somebody's got some new kind of strain gauge that can be surgically
attached to human tendon.)

Ken
 
T

Tim McNamara

Guest
In article
<[email protected]>,
"Ken Roberts" <[email protected]> wrote:

> Tim McNamara wrote
> > What's unmeasureable about it? Strain gauges on the cranks will
> > measure the force magnitude and direction.

>
> Strain gauges measure the force to the pedal or the crank. They do
> not measure the force exerted by the hip-flexion muscles, which is
> what I and some other people are talking about in this thread -- and
> what some scientific researchers have been working hard to try to
> estimate by clever means.
>
> (Unless somebody's got some new kind of strain gauge that can be
> surgically attached to human tendon.)


The force at the pedal is the force that counts. The rest of the stuff
you're on about is pretty much fine as frog's hair.