Aye, but said losses don't occur as a result of the motion (or the energy transfer) per se, which is what you have claimed now for, what, almost a decade? That is, in a frictionless environment with absolutely rigid limbs (and a fixed ankle joint), that little metal man will just pedal and pedal and pedal and pedal and pedal and pedal...

Let's see if I can further confuse you:

Picture a perfectly frictionless car coasting along a perfectly frictionless, perfectly flat track in a perfect vacuum...how long will it continue to coast? The answer, of course, is "forever", because there is no means by which the kinetic energy can leave the system. Now picture what happens when the same car encounters a series of roller-coaster hills that entail no net gain/loss in elevation but nonetheless bring it almost-but-not-quite to a complete stop at the top of each one, before it picks up speed again as it coasts down the other side. How long does it continue to coast in this situation? The answer, again, is "forever"...but the only way you can agree with that statement is to reject your prior claims, because the situation is exactly the same w/ respect to pedaling.

Who says I'm trying to teach him? :-)

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http://bikeblather.blogspot.com/

You lost him right there...in fact, you probably made his head explode...

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http://bikeblather.blogspot.com/

If you say so. Guess we have that perpetual motion machine afterall, even without the need to invoke perfectly rigid components. I must have been mistaken. So glad you chimed in.

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Frank,
An original Ironman and the Inventor of PowerCranks

I knew you were going to claim the exception of the perfectly rigid parts. If we eliminate your impossible exception my statement is correct.
No, I can agree with all of that.

The problem I am trying to discuss is whether there is any energy loss inherent in real materials trying to absorb or transfer the kinetic energy contained in another object. That is what the pedaling motion requires. Show us how you make that happen without loss please.

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Frank,
An original Ironman and the Inventor of PowerCranks

Ditto.

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Giovanni Ciriani
http://www.GlobusSHT.com

Please explain why without invoking the use of materials that exist only in the imagination.

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Frank,
An original Ironman and the Inventor of PowerCranks

Because the pedaling motion, the way we defined it here, has nothing to do with materials: we said it woud be the same either in a MMF, or in any other material. Energy loss can only happen either through transfer of work to an outside recipient (something absorbing force), or through development of heat (for instance a brake that transforms the force on the brake into heat). The MMF system interacts with the outside world only through the frame on which the cranks are rotating, and if you want through the hips. The forces the MMF system develops on the hip and on the crank axle are not translating. Therefore neither the equally opposing forces from the outside system are translating. Only a translating force (or turning torque) develops work. Ergo the outside system is not absorbing or subtractoing work from the MMF.

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Giovanni Ciriani
http://www.GlobusSHT.com

Because the pedaling motion, the way we defined it here, has nothing to do with materials: we said it woud be the same either in a MMF, or in any other material. Energy loss can only happen either through transfer of work to an outside recipient (something absorbing force), or through development of heat (for instance a brake that transforms the force on the brake into heat). The MMF system interacts with the outside world only through the frame on which the cranks are rotating, and if you want through the hips. The forces the MMF system develops on the hip and on the crank axle are not translating. Therefore neither the equally opposing forces from the outside system are translating. Only a translating force (or turning torque) develops work. Ergo the outside system is not absorbing or subtractoing work from the MMF.[/reply] Oh phooey. I am sorry, the MMF system, in my opinion, includes the rider and the wheels but it doesn't have to. All it has to include is the legs and the cranks. But, using the usual definition, the MMF model only interacts with the outside world through the wheels. The pedaling motion involves the reciprocal motion of the thigh and the rotary motion of the foot. The reciprocal motion of the thigh involves substantial kinetic energy variation during the motion. if you choose the constraint that the MMF cannot cannot absorb or subtract work from the MMF you are requiring the speed to be constant, which requires the rotation of the cranks to be constant. Therefore, if the materials cannot absorb the variation in energy seen in the thigh then the energy of the system is not constant which means energy is being created and destroyed. Under these circumstances, the model is violating the first law, an impossibility.

But, under the same constraints, if you allow the materials to absorb and return the energy to maintain the energy of the system as a constant it would be possible to keep the energy of the system constant so the first law would not be violated. However, this requires the materials to act as perfect springs, to return all the energy that it abbsorbs. Perfect springs do not exist in the real world (I am quite certain their existence would violate the 2nd law although I suspect that Tom A. would argue that since entropy is not decreased the law is not violated) so such absorbtion results in some energy loss in the real world, the amount of loss depends on the material.

If you use your MMF system, a system, if I read it right, that eliminates the chain and the wheels so no kinetic energy can be transferred to the outside, another problem develops. While the system cannot transfer energy "outside" the model that doesn't mean there are no losses, at least when you use real materials. The problem comes, again, from the variation in energy in the thigh. To avoid violating the 1st law the rotational speed of the pedals must vary considerably around the circle to keep the energy of the system constant. This simple transfer of energy, by itself, dictates, because of the second law, that there be an entropy increase or a decrease in the amount of energy available to do work, the rest being transferred to heat. This occurs again because acceleration requires force which, when using real world materials, material deformation.

You cannot describe an MMF system that uses real world materials that doesn't involve energy loss during the pedaling motion. The second law dictates this to be true. Any reasonable kinetic analysis comes to the same conclusion. The only question is the amount of the loss.

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Frank,
An original Ironman and the Inventor of PowerCranks

"How is it you feel comfortable using a model that doesn't allow any internal losses to analyze how large the internal losses, that must be there, really are?"

Andrew, Tom A, Giovanni, Lidl -- I understand where the inefficiencies of pedalling are. You've been using Newtonian mechanics in an inertial frame of reference, but relativity is where it's at. Newtonian mechanics are just an approximation. I mean, this has to be it; what else could it be? Just look at some of the basic formulas for relativity: the square of the speed figures prominently, so it fits right in. Why, even perfectly rigid elements distort when space itself warps, so we can all be right about that part. And actually, we can't really know how much the distortion is if you don't know how much space itself distorts. Don't try to tell me that the differences are minor when you don't know how big they are! How can you feel comfortable using a simplified Newtonian model that doesn't allow for the relativistic adjustments to analyze how large the relativistic adjustments, that must be there, really are? By process of elimination, the losses can be found in the difference between Newton's law and
Einstein's. Clearly you don't understand, because you are using a model that ignores reality. Einstein showed that Newton was wrong years ago; you are violating physics. Show me a thorough analysis in which you account for all losses using only relativistic mechanics; also perform numerous tests up to and including pedalling at the speed of light; also write the results in triplicate so I can utterly ignore their salient content more repeatedly; and generally do whatever I tell you to after I change my position when you're done. Good luck. And LOL.

And don't you try to tell me I'm wrong -- you know I'm onto something, and if you disagree, that would be recalcitrant.

Did a little more reading to see if I could find a little more support for my position. Found this.

http://wapedia.mobi/...ius-Duhem_inequality



It would seem that whenever a real material is deformed entropy must increase. Whenever a force is applied to a real material then both the pusher and the pushee must be deformed since there are no perfectly rigid real materials. Any acceleration (acceleration occurs only in the presence of force) of a real material (such as the reciprocating movement of the thigh when pedaling) must involve entropy increase. An entropy increase can be seen as an energy decrease (wikipedia article on entropy and energy dispersal). Or, in real world terms, the ability to do work is decreased through the production of heat energy.

Maybe we can soon move on and discuss how much energy is dissipated during the pedaling motion, not debate whether it occurs. While I doubt that will occur but hope springs eternal.

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Frank,
An original Ironman and the Inventor of PowerCranks

I also found this paper that goes to some of these issues.
Comment: The losses observed were most closely related to pedal speed. There are two different possible main contributors to this "pedal speed" loss IMHO. One has to do with the loss of muscle contractile efficiency as the contractile speed gets faster and faster. This has been brought up in this thread earlier and I will post the images that relate to this again. Note that the pedal speeds attained in the study are probably never more than 60% of the maximum for any individual so I don't see how these graphs can explain the curvelinear nature of the losses described in the above study.




Therefore, it would look like one must also invoke some additional losses to account for the entirety of the losses seen due to pedal speed. The most likely candidate in my opinion are the losses I have been talking about, hysterisis losses due to material deformation from continuous energy transfer throughout the system from the variation in energy in the thigh. Whether the increase in pedal speed is coming from increasing the crank length or increasing the cadence, either way the energy variation is increased and the losses I am talking about should increase with the square of the pedal speed.

Anyhow, these losses and the shapes of the curves must be explained if one hopes to understand what is going on. I submit that they are the result of several different losses but that the two biggest factors are muscle inefficiencies due to increased contractile speed and increased hysteresis losses. If you disagree you are welcome to put forth your own hypothesis to explain the data.

Anyhow, to suggest that pedaling losses are trivial in view of this data (73 to 290 watts) is ludicrous. All that can be contested is the source of those losses and how they can be best minimized, not whether losses exist or are they significant enough to worry about.

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Frank,
An original Ironman and the Inventor of PowerCranks

I have also been able to copy this figure from the paper showing the UNLOADED energy cost (losses) with pedal speed. 290 watts are being required just to make the cranks go around folks at high pedal speeds. Even at low pedal speeds, the energy requirement is not trivial.

Why does it vary the way it does? Since no work is being done, where is that energy going folks? Why is the delta efficiency curve leveling off while the energy cost curve is increasing slope? If you can answer all of those questions correctly you probably have a pretty good understanding of what is going on. Could one use this figure to make an argument for a "most efficient" pedal speed for racing? I think I could.

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Frank,
An original Ironman and the Inventor of PowerCranks

A few comments:

1) Are you now admitting that a frictionless, perfectly rigid stick figure pedaling in a vacuum would continue to pedal forever? If so, that is a reversal of what you have been claiming for the better part of a decade.

2) The data you posted demonstrates that you are still confusing physics with physiology. Until you understand the former you can't understand the latter, so let's stick with it for now (as Tom A. already suggested).

3) You should ignore the metabolic costs of unloaded pedaling. Again as already discussed in this thread, the fact that there is no external load means that we use our muscles differently than when there is one, making it an "apples-to-oranges" comparision. This is why A) the cost of unloadded pedaling is significantly greater than the y-intercept of the VO2-power relationship, and B) delta efficiency is considered the best measure of muscle efficiency.

4) Re. your last sentence in your post immediately preceeding this one: you don't need to measure/calculate the cost of unloaded pedaling or delta efficiency to determine the most efficient (not optimal) cadence. The latter is simply the cadence that results in the highest gross efficiency at a particular power; measurements/calculation in addition to/beyond gross efficiency are only necessary when attempting to determine mechanisms.

5) You've confused other issues/made other incorrect statements in these two most recent posts, but I don't have time to correct them all at the moment, and attempting to do so would only confuse you further.

Phooey. ;-)

Yes, for the purposes of this argument I will agree with that since we know that such a machine is impossible to build and it is not the scenario I am interested in discussing. So, can we forget the perfect stick figure and stick with the real world
I am? Perhaps you could enlighten me as to where I am confused. Is there a difference between physics watts and "metabolic" watts? Exactly what is that difference.
McDaniel's data has a couple of things in it that are bothering me. Perhaps you could help me to better understand. Papadapalous, Tom, you, and about everyone else on the other side of this argument agree that there are losses associated with unloaded pedaling but as soon as the chain is loaded those losses will disappear because they can now be transferred to the wheel. While MdDaniel's data doesn't address this directly why is it that I suspect that when they are pedaling the 195mm cranks at 100 rpm (something almost everyone can do unloaded) and needing 290 metabolic watts to do this trick, I suspect that each and everyone of them will have difficulty sustaining 290 watts at the wheel for any length of time as soon as the chain is loaded. And, if it is true that all this energy is transferred to the wheel as soon as the chain is loaded, how on earth could they ever ride at anything less than 290 watts when pedaling at 100 rpm on 195 mm cranks? I am sure they can but how do they do it? Any ideas?

Oh, and I find the delta efficiency numbers interesting. The delta (muscle) efficiency is still increasing, even at 100 rpm. Where would you think this puts them on the contractile efficiency with shortening velocity part of the curve? The delta efficiency numbers obtained are substantially higher than I have ever seen documented for a loaded cyclist, they are even higher than those recorded by Coyle in Lance. How do you explain this?
To which post are you referring. I presume the one in which I asked if one could predict from fig 4 where the optimum pedal speed would be? I simply asked if you thought you could. I guess your answer is "no" since you dodged the question by saying you don't have to, all you have to do is test it directly.
I guess you don't have time to even list them as to what they are, just leave the impression that . . .

Anyhow, you are probably right, your "corrections" would only confuse me more. (Actually, it is rare that you ever "correct" anyone, mostly what you do is simply pronounce them wrong then go away.) As I stated above, I am really confused as to how any of those riders would ever be able to ride at a light power when there is 290 watts of power in the legs just waiting to be automatically transferred to the chain and wheel as soon as it can be loaded, in view of what I have been told to be the truth earlier in this thread, and others. Again, help me here. I am trying to get as smart as you. I know it will be hard, but I am trying.

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Frank,
An original Ironman and the Inventor of PowerCranks

Well hot d***! It is about time!


No, we cannot, because it is that hypothetical scenario that allows the sources of the losses during pedaling to be quantified (using inverse dynamics).

I am? Perhaps you could enlighten me as to where I am confused.[/reply]
The fact that you insisted on dragging physiological data into the discussion demonstrates that you were (and apparently still are) unable to differentiate between the physics and the physiology (and as has been pointed out before, you need to understand the former to understand the latter). Once that is settled, then - and only then - can we move on (which is I am not responding to your other comments).

Metabolic watts.

Well, you are right, your answers only confuse me. So, you are telling me that you are using a model that doesn't allow any internal losses to be the basis for calculating real world internal losses using inverse dynamics? Exactly how is that done? Don't you think one might be able to choose a better model for this purpose than one that predetermines the answer to be zero?[/reply] I am? Perhaps you could enlighten me as to where I am confused.[/reply]
The fact that you insisted on dragging physiological data into the discussion demonstrates that you were (and apparently still are) unable to differentiate between the physics and the physiology (and as has been pointed out before, you need to understand the former to understand the latter). Once that is settled, then - and only then - can we move on (which is I am not responding to your other comments).[/reply] Exactly which physiological data did I insist on dragging into the discussion that is making it impossible to differentiate this stuff? I thank you so much for telling me I am getting it wrong but I need help understanding exactly what it is that I am getting wrong. Help me here. I am sure you can do it, after all doctor does mean teacher.

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Frank,
An original Ironman and the Inventor of PowerCranks

Exactly what are metabolic watts? I have never heard of this term before? Wonder what it could mean? Perhaps it is the watt equivalent in energy consumption needed to turn the legs unoaded (since it is impossible for them to generate any real watts since the bike is unloaded so can do no real work) so it is easier for the reader to compare apples and oranges. What do you think?

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Frank,
An original Ironman and the Inventor of PowerCranks

Somehow this thread remind me of this clip: http://www.youtube.com/watch?v=EbVKWCpNFhY

At some point... arguing further is just pointless.

You're right, the way that I stated it was confusing. What I should have said was that that hypothetical scenario has been repeatedly presented so that you will understand how the sources of various losses can be quantified (using inverse dynamics). Specifically, by recognizing that - in the absence of friction, limb bending, etc. - there is absolutely no energy lost in the interconversion of potential and kinetic energy, you would now be in a position to apply this correct understanding of the fundamental physics to the in vivo situation. However, despite your grudging acknowledgement that you have been wrong all along regarding the basic physics ("...for the sake of the present discussion..."), I still don't think you really get it.


Force pedal measurements + high speed film + knowledge of basic physics = ability to quantify the power "flow" through the ergometer + rider system. What such measurements reveal is that there is very little inefficiency "downstream" of when the limbs are set in motion - rather, essentially all of the inefficiency arises "upstream".




Martin's.

You guessed correctly: metabolic rate measured in watts. For comparison, standard resting metabolic rate for a 70 kg person would be ~80 W.