The pedaling technique thread

[acoggan]

So, let me get this straight.

I make the assertion that skeletal muscle contracts with an energy efficiency of about 40%;
and the average cyclist has an overall energy efficiency of about 20%;
and that no scientist has ever been able to quantitfy where these losses occur between the muscle and the wheel.

And, all you, a published exercise physiologist, can add to the conversation is an ad hominem attack?

You really know how to make a fella feel secure in his argument. Thanks

1. Your assertion that muscle contracts with an efficiency of about 40% is incorrect.

2. Statements of fact are not ad hominem attacks.

 

[sciguy]

LOL. Might I remind you that I went to medical school. That 40% number was part of the basic physiology course in the first year. I would guess that means it is pretty well established.

Let me get this straight. You're contending that your recollection of a course you took nearly a half century trumps the web site you yourself linked to?

How about the information from this site http://www.tiem.utk.edu/~gross/bioed/webmodules/ATPEfficiency.htm or don't you trust what it has to say?

"Under standard conditions, Ereact = -686 kcal/mol and EATP = -7.3 kcal/mol. From the chemical reaction for the formation of ATP, we see that 36 molecules are formed. Therefore we calculate the efficiency as

In other words, only about 38.3% of the energy released from the reaction of glucose with oxygen is captured in ATP bonds."

So we're down to 38% of the initial energy content before a muscle fiber even starts to contract!

If it has changed I suspect someone like Dr. Coggan will come forward and give evidence to the contrary. Well, the 40% is the efficiency of converting energy into work in skeletal muscle. You are reading it wrong.

I would contend that it's you who is reading it wrong. Please provide a link to any site that clearly states that muscles have an efficiency of 40% in converting glucose to muscular work. This should be easy for you as it's so well know. Just for the record, what text did you use in your freshman physiology course that you remember oh so clearly?

Hugh

 

[FrankDay]

1. Your assertion that muscle contracts with an efficiency of about 40% is incorrect.

Then, enlighten the group as to what the correct number is. (Let's use optimal efficiency since, afterall, a muscle contracting isometrically has a mechanical efficiency of zero since no work is done) And, then after that, please quantify where the losses occur between that number to account for the 16-26% cycling efficiency found in the literature.

2. Statements of fact are not ad hominem attacks.

They can be..

An ad hominem (Latin for "to the man" or "to the person"[1]), short for argumentum ad hominem, means responding to arguments by attacking a person's character, rather than to the content of their arguments. When used inappropriately, it is a fallacy in which a claim or argument is dismissed on the basis of some irrelevant fact or supposition about the author or the person being criticized.[

 

[FrankDay]

Let me get this straight. You're contending that your recollection of a course you took nearly a half century trumps the web site you yourself linked to?

How about the information from this site http://www.tiem.utk.edu/~gross/bioed/webmodules/ATPEfficiency.htm or don't you trust what it has to say?

"Under standard conditions, Ereact = -686 kcal/mol and EATP = -7.3 kcal/mol. From the chemical reaction for the formation of ATP, we see that 36 molecules are formed. Therefore we calculate the efficiency as

In other words, only about 38.3% of the energy released from the reaction of glucose with oxygen is captured in ATP bonds."

So we're down to 38% of the initial energy content before a muscle fiber even starts to contract!

Or not

In the second procedure, stimulation began before stretching and continued during the first part of shortening. In this case, the efficiency attained values of approximately 35% in sartorius, 50% in EDL, and 40% in soleus. These values are in rough agreement with those measured in vivo during running.

I would contend that it's you who is reading it wrong. Please provide a link to any site that clearly states that muscles have an efficiency of 40% in converting glucose to muscular work. This should be easy for you as it's so well know. Just for the record, what text did you use in your freshman physiology course that you remember oh so clearly?

Hugh

But, for the sake of argument (discussion), lets assume your numbers are correct, that 40% efficiency in getting ATP and 68% efficiency in performing contraction, resulting in a max possible cycling efficiency of about 28%. Now, the published range of cycling efficiency ranges from 16 to 26%. Do you accept the efficiency of the average cyclist is 20%? Where are the losses between 28 and 20% occurring. If the rider could increase their efficiency from 20 to 28% that would give them a 40% increase in power. If the 16% efficiency rider could increase their efficiency to 28% that would result in a 75% increase in power all without improving the ability of the muscles. Are you willing to ignore these possible areas of improvement simply because they are seemingly smaller than what I felt (it really isn't as I feel many of the losses between the 40% I mentioned and what is possible cannot be overcome such that the max cycling efficiency we might expect possible would be in the 28-30% range.

So, lets discuss losses that are present that can be overcome. Do you disagree that a muscle contraction that causes a pedal force opposite to the direction of pedal movement is a preventable loss of cycling efficiency? You guys are too focused on this number is wrong and not at all focused on how, theoretically, pedaling technique could be improved to improve performance.

 

[JayKosta]

...
So, lets discuss losses that are present that can be overcome. Do you disagree that a muscle contraction that causes a pedal force opposite to the direction of pedal movement is a preventable loss of cycling efficiency?
...
and not at all focused on how, theoretically, pedaling technique could be improved to improve performance.

-----------------------------------------------------------
I think the important question is:

'HOW can maximum 'chain power' be produced in a 'race' type event, where efficiency is a secondary concern. But of course the efficiency must be adequate for successful completion of the event.
And, is there a 'pedaling technique' for this?
---

A related (but perhaps uninteresting question) is:

'What is the maximum amount of 'chain power' that can be produced per unit of ATP being used' ? And is there a 'pedaling technique' for this?

This is a measure of physiological efficiency to produce power and might only be of interest for extreme endurance events, since the rate of ATP usage might be low to give highest efficiency.

Jay Kosta
Endwell NY USA

 

[FrankDay]

-----------------------------------------------------------
I think the important question is:

'HOW can maximum 'chain power' be produced in a 'race' type event, where efficiency is a secondary concern. But of course the efficiency must be adequate for successful completion of the event.
And, is there a 'pedaling technique' for this?
---

A related (but perhaps uninteresting question) is:

'What is the maximum amount of 'chain power' that can be produced per unit of ATP being used' ? And is there a 'pedaling technique' for this?

This is a measure of physiological efficiency to produce power and might only be of interest for extreme endurance events, since the rate of ATP usage might be low to give highest efficiency.

Jay Kosta
Endwell NY USA

Yes, those are interesting questions. One cannot begin to address them until one understands the losses between the muscle and the wheel. My guess is that what is optimum for one situation will be pretty much optimum for every situation with small variations because efficiency affects how much energy is consumed at any given power (important for endurance events) and how much power one can generate at any given energy expenditure (important for short events). Everyone understands some of these efficiency losses and tries to minimize them. For instance, everyone knows that bearings need to be well oiled and smooth running to minimize bearing loss. Chains need to be clean and oiled and old chains replaced to minimize bearing loss. Tires need to be properly inflated and some materials cause less loss than others.

What we are trying to discuss here are the losses that occur between the muscle and the chain yet, it seems, that some simply don't want to discuss it because it goes beyond their difficulty level. It doesn't matter what the maximum efficiency of the contracting muscle if there are correctable losses between the muscle and the chain. The problem is we cannot correct them unless we understand what they are. How the heck can we understand these issues if the gurus simply refuse to discuss the issue and personally attack those who do. Oh well, it is the internet.

 

[JamesCun]

...is pretty well established...pretty well established...pretty well established...I have conjectured...better technique...I see potentially occurring in most people...If we assume

So, you made assumptions, conjectured something, made a product that fixes technique (with no evidence of what better technique is) and then tested in a very haphazard way the improvement seen, without any controls and no ability to demonstrate cause and effect.

Do I have that right?

 

[FrankDay]

So, you made assumptions, conjectured something, made a product that fixes technique (with no evidence of what better technique is) and then tested in a very ahphazard way the improvement seen, without any controls and no ability to demonstrate cause and effect.

Do I have that right?

No.

Would you like to address the issue of trying to quantify the losses between the muscle and the chain?

 

[JamesCun]

No.

Would you like to address the issue of trying to quantify the losses between the muscle and the chain?

My original question that you have avoided answering:

"What testing have you done in this area? If this is central to what can be improved, as a scientist, what have you done to study this topic?"

I'm assuming that your lack of an answer suggests that you haven't studied what happens to the power between the muscle and chain. Wouldn't that be a key concept to showing what a better pedaling technique is?

 

[JamesCun]

No.

Would you like to address the issue of trying to quantify the losses between the muscle and the chain?

Just to play along here. (the specific numbers are irrelevant for this portion of the discussion)

Does the efficiency of the muscle contraction, you state at 40%, represent a single motor unit, muscle group or limb segment? Or, is it the maximal force output that can be exerted through the skeletal system?

I'd assume that due to the orientation of different muscles, the muscle fibres and various joint angles/orientations and insertions, that muscle contraction has a much different impact on actual force output in all the different situations. Have you analyzed all the joint angles, and muscle attachments and determined the maximal force output in the pedalling cycle based on a given energy input?

 

[FrankDay]

My original question that you have avoided answering:

"What testing have you done in this area? If this is central to what can be improved, as a scientist, what have you done to study this topic?"

I'm assuming that your lack of an answer suggests that you haven't studied what happens to the power between the muscle and chain. Wouldn't that be a key concept to showing what a better pedaling technique is?

First, some of my thoughts are based upon well known principles. While it is true I graduated from medical school I also, before medical school, graduated from a rather well respected engineering school. The efficient transfer of power involves rather well understood engineering principles that go back many centuries, around the time I graduated from that well-known engineering school. Anyone well-versed in this area who looks at the pedaling dynamic of the average cyclist would know there is room for huge efficiency improvements. The fact that you are not well-versed in this area I don't find particularly compelling to cause me to modify my opinion.

What testing have I done in this area? Well, now that I have my hands on a pair of iCranks I have actually measured the pedaling technique to those who have trained a long time on my product, showing that the product actually does change the way people pedal given enough time. See the below technique done by pro triathlete Petr Vabrosek, after approximately 10 years on PowerCranks.

This pattern corresponds to the university studies that have demonstrated training with PowerCranks actually change the timing of the contraction of the various leg muscles. And corresponds to the university studies that have shown a cycling efficiency improvement after a period of time training on the PowerCranks. Further, I have measured the pedaling technique of those who have not trained on the product and notice it is substantially different from the PowerCranker being particularly deficient from 9 to 1 on the pedal circle.

So, my thoughts are based mostly upon theoretical considerations and these thoughts have been partially supported by independent studies.

Now, what testing have you done to discredit these thoughts so you can add to the debate (if that is what the wailing of the other side represents)? ... I thought so.

So, can you get off the personal attacks and stay on topic. If you have any data to suggest there are not large losses between the muscles and chain please put them forward. Or, if you have any data that supports the losses are large due to a different mechanism (and nothing can be done about them) than I have proposed please put those forward. Otherwise, you are wasting a lot of band width continuing on this tact.

 

[FrankDay]

Just to play along here. (the specific numbers are irrelevant for this portion of the discussion)

Does the efficiency of the muscle contraction, you state at 40%, represent a single motor unit, muscle group or limb segment? Or, is it the maximal force output that can be exerted through the skeletal system?

For the purposes of this discussion I am considering it to be the muscle group. That is what most of the experimental data is based upon and is the maximum efficiency seen only at a certain force and contraction velocity.

I'd assume that due to the orientation of different muscles, the muscle fibres and various joint angles/orientations and insertions, that muscle contraction has a much different impact on actual force output in all the different situations. Have you analyzed all the joint angles, and muscle attachments and determined the maximal force output in the pedalling cycle based on a given energy input?

No I haven't. I suspect that such considerations could result in some loss. However, what I have looked at is the resultant forces on the pedal of the various muscle contractions. Resultant forces opposite to the motion of the pedal seem to me to be particularly deleterious to a high cycling efficiency.

As I have said, if one doesn't understand all of the losses between the muscle and the chain one cannot know what can be mitigated and which cannot. For instance, there is some joint friction that cannot be eliminated but it might be reduced by lowering cadence (I don't know). I think it fair to say that muscle contraction against the direction of motion is probably not good. Or, that failure to use a muscle when its action would be particularly advantageous also seems not good. Why haven't the exercise physiologists looked into this? Where is Dr. Coggan when you need him?

 

[sciguy]

First, as a scientist, one must trust the work of other scientists.

and yet you seem to completely ignore the work of others on a regular basis.

But, for the sake of argument (discussion), lets assume your numbers are correct, that 40% efficiency in getting ATP and 68% efficiency in performing contraction, resulting in a max possible cycling efficiency of about 28%. Now, the published range of cycling efficiency ranges from 16 to 26%. Do you accept the efficiency of the average cyclist is 20%? Where are the losses between 28 and 20% occurring.

The variation in efficiency due to muscle fiber type has been pointed out to you many times in the past. I'll do it once more for the folks reading this thread.

We can thank Coyle EF1, Sidossis LS, Horowitz JF, Beltz JD back in 1992 for this study. http://www.ncbi.nlm.nih.gov/pubmed/1501563

It's especially interesting to see that their data shows efficiency would vary by a factor of 2 going from 100% type I fibers to 100% type 2 fibers. Since it's well established that athletes vary a good deal in their muscle fiber makeup and that fiber composition correlates strongly with efficiency we suddenly come to the conclusion that your concern regarding technique is very likely completely unfounded. Obviously you have a huge vested interest in getting people to believe there is a problem when in all likelihood there is none.

 

[sciguy]

Let me get this straight. You're contending that your recollection of a course you took nearly a half century trumps the web site you yourself linked to?

Please provide a link to any site that clearly states that muscles have an efficiency of 40% in converting glucose to muscular work. This should be easy for you as it's so well know. Just for the record, what text did you use in your freshman physiology course that you remember oh so clearly?

Hugh

Frank,

You as an trained engineer must realize that any process will be limited in its maximum efficiency by a primary step that reduces the efficiency of production of its fuel source. Come on, this is engineering 101 here.

How Efficient is Aerobic Respiration?

a. Difference in energy content between glucose and O2, and products CO2 and H2O is 686 kilocalories.
b. The ATP third phosphate bond has energy content of 7.3 kilocalories, 36 ATP are produced per glucose breakdown totaling 263 kilocalories.
c. Efficiency is 263/686 or 39%.
d. Sixty-one percent is lost as heat; in birds and mammals, this heat assists in maintaining body temperature.



I'm still waiting and no your link did not clearly state that muscles have an efficiency of 40% in converting glucose to muscular work. For all I could tell from the link you posted they were looking at the efficiency of ATP to work step. What it did show is that there is a huge variation in efficiency between different muscle groups in doing work as I and others have long contended. We know for example that the hip flexors are composed of predominantly fast twitch fibers and are therefore inherently less efficient than the glutes and quads of most athletes.

Hugh

 

[sciguy]

What testing have I done in this area? Well, now that I have my hands on a pair of iCranks I have actually measured the pedaling technique to those who have trained a long time on my product, showing that the product actually does change the way people pedal given enough time. See the below technique done by pro triathlete Petr Vabrosek, after approximately 10 years on PowerCranks.

OMG, this silly diagram again of Peter putting out less power than I would as a 60 year old just starting to warm up before the beginning of a workout. It would be a lot more instructive to see what he looks like outputting double or triple the power. It is interesting how asymmetric this long time Powercranker is pedaling. I thought Powercranks were supposed to eliminate asymmetries? Not sure where I heard that one?

Hugh

 

[acoggan]

Just to toss one more factoid into the mix: not all of the O2 consumed by the body as a whole during cycling goes to the muscles actually producing the external power. That is, there is an "overhead cost" due to increased respiration, cardiac work, use of stabilizing muscles, a possible Q10 effect in organs such as the liver, etc. What this means is that the contracting muscles themselves are even more efficient than the, say, 23/38 = 60% suggested by measurement of gross efficiency and recognition of energy losses in the production of ATP. IOW, our pedaling muscles have an efficiency that rivals, if not exceeds, that of highly-efficient electric motors.

Ain't evolution wonderful?

 

[acoggan]

They can be..

Again, statements of relevant facts are not ad hominem attacks (esp. when you're the one who constantly refers to your ancient history to bolster your arguments).

 

[FrankDay]

and yet you seem to completely ignore the work of others on a regular basis.



The variation in efficiency due to muscle fiber type has been pointed out to you many times in the past. I'll do it once more for the folks reading this thread.

We can thank Coyle EF1, Sidossis LS, Horowitz JF, Beltz JD back in 1992 for this study. http://www.ncbi.nlm.nih.gov/pubmed/1501563

It's especially interesting to see that their data shows efficiency would vary by a factor of 2 going from 100% type I fibers to 100% type 2 fibers. Since it's well established that athletes vary a good deal in their muscle fiber makeup and that fiber composition correlates strongly with efficiency we suddenly come to the conclusion that your concern regarding technique is very likely completely unfounded. Obviously you have a huge vested interest in getting people to believe there is a problem when in all likelihood there is none.

Ugh, that data involves gross and delta efficiency which includes the drop in efficiency between the muscle and the wheel. Since the current discussion solely about the drop in efficiency between the muscle and the pedal it really doesn't add anything to the discussion. Whatever the starting point of the muscle efficiency the question I am trying to discuss here is how can we minimize the drop in efficiency between the muscle and the pedal to maximize the performance of the cyclist.

 

[FrankDay]

Frank,

You as an trained engineer must realize that any process will be limited in its maximum efficiency by a primary step that reduces the efficiency of production of its fuel source. Come on, this is engineering 101 here.

How Efficient is Aerobic Respiration?

a. Difference in energy content between glucose and O2, and products CO2 and H2O is 686 kilocalories.
b. The ATP third phosphate bond has energy content of 7.3 kilocalories, 36 ATP are produced per glucose breakdown totaling 263 kilocalories.
c. Efficiency is 263/686 or 39%.
d. Sixty-one percent is lost as heat; in birds and mammals, this heat assists in maintaining body temperature.



I'm still waiting and no your link did not clearly state that muscles have an efficiency of 40% in converting glucose to muscular work. For all I could tell from the link you posted they were looking at the efficiency of ATP to work step. What it did show is that there is a huge variation in efficiency between different muscle groups in doing work as I and others have long contended. We know for example that the hip flexors are composed of predominantly fast twitch fibers and are therefore inherently less efficient than the glutes and quads of most athletes.

Hugh

You guys just don't seem to get it. For the purposes of this discussion the muscle should be seen as a black box with a certain efficiency when measured at the output of the black box. Then, when the efficiency is measured at the pedal there is a different, lower, efficiency. It doesn't really matter if the drop is from 40% to 20% or 30% to 20%, as long as there is a drop (which there is). This means there have to be additional energy losses between the two measurement points. The question is, where are those losses? If this were a question on the SAT you guys would be in big trouble because you keep wanting to talk about muscle efficiency when the question is about losses after the muscle. We can assume there might be some loss due to knee joint friction but I would be surprised if joint friction alone can account for a 33-50% drop in efficiency. That would mean at 50% that at 150 pedal watts the knee joint would be wasting 150 watts and would, with enough time, get pretty hot (think incandescent light bulb). It doesn't happen. There have to be other sources of loss. Explain where they are and whether they are reducible or not? I personally think there are several explanations but the bulk of these losses come from ineffective coordination of the muscles contracting them when they can do little work. We know this happens through analysis of pedal forces. It should also be correctable.

 

[FrankDay]

Just to toss one more factoid into the mix: not all of the O2 consumed by the body as a whole during cycling goes to the muscles actually producing the external power. That is, there is an "overhead cost" due to increased respiration, cardiac work, use of stabilizing muscles, a possible Q10 effect in organs such as the liver, etc. What this means is that the contracting muscles themselves are even more efficient than the, say, 23/38 = 60% suggested by measurement of gross efficiency and recognition of energy losses in the production of ATP. IOW, our pedaling muscles have an efficiency that rivals, if not exceeds, that of highly-efficient electric motors.

Ain't evolution wonderful?

Now if we could get you to address the efficiency loss between that high efficiency "electric motor" and the efficiency measured at the pedals (around 20%), definitely not in the "high efficiency electric motor" class. And, how do we explain the huge gross efficiency range seen in cyclists (16-26%)? If we don't understand those losses then we really don't understand much about cycling physiology/mechanics, do we?, as those are the largest losses seen in cycling power production chain after the muscle. yet it has been ignored by the research community as near as I can tell.

 

[FrankDay]

Again, statements of relevant facts are not ad hominem attacks (esp. when you're the one who constantly refers to your ancient history to bolster your arguments).

Like I said, if that is all you got to counter my arguments then it makes me feel good. LOL.

 

[JamesCun]

Now if we could get you to address the efficiency loss between that high efficiency "electric motor" and the efficiency measured at the pedals (around 20%), definitely not in the "high efficiency electric motor" class. And, how do we explain the huge gross efficiency range seen in cyclists (16-26%)? If we don't understand those losses then we really don't understand much about cycling physiology/mechanics, do we?, as those are the largest losses seen in cycling power production chain after the muscle. yet it has been ignored by the research community as near as I can tell.

Ignored by you as well. Go out and get the research done. So far in this thread, you've just put it back to others to validate your assumptions and conjecture.

And you should really learn what a personal attack is. Nothing I've written here is even remotely in that ballpark.

 

[FrankDay]

Ignored by you as well. Go out and get the research done. So far in this thread, you've just put it back to others to validate your assumptions and conjecture.

And you should really learn what a personal attack is. Nothing I've written here is even remotely in that ballpark.

No, it hasn't been ignored by me (if it had been we wouldn't have this thread). This is a pedaling technique thread. I believe a lot of those losses are do to poor (but, mostly, correctable) pedaling technique. This is an easy argument to make to someone practiced in the mechanical engineering area by just looking at the work that has already been done including already demonstrated typical pedal forces, ability to change the pedaling coordination to something that is theoretically more efficient, and the ability to increase gross pedaling efficiency by using a tool designed to change the pedaling dynamic.

Anyhow, I am simply making the argument based upon theory and experience. It is a weak counter to just say "you haven't proved your case" when you cannot provide an equally compelling counter theory to explain the losses. The losses are there. WHY? Can they be minimized? If they can be minimized are you, as a competitive athlete, interested in doing so? If not I suggest you move on. If you are perhaps you should pay better attention.

 

[JamesCun]

No, it hasn't been ignored by me (if it had been we wouldn't have this thread). This is a pedaling technique thread. I believe a lot of those losses are do to poor (but, mostly, correctable) pedaling technique. This is an easy argument to make to someone practiced in the mechanical engineering area by just looking at the work that has already been done including already demonstrated typical pedal forces, ability to change the pedaling coordination to something that is theoretically more efficient, and the ability to increase gross pedaling efficiency by using a tool designed to change the pedaling dynamic.

Anyhow, I am simply making the argument based upon theory and experience. It is a weak counter to just say "you haven't proved your case" when you cannot provide an equally compelling counter theory to explain the losses. The losses are there. WHY? Can they be minimized? If they can be minimized are you, as a competitive athlete, interested in doing so? If not I suggest you move on. If you are perhaps you should pay better attention.

I guess bold makes it better...

You haven't shown that your initial assumption of muscle efficiency to pedalling efficiency is accurate. Several people in this thread challenge your initial assumption. If that initial assumptions is not correct, or is vastly overstated, then your subsequent discussion is less relevant or completely irrelevant, depending on how accurate your initial assumption was.

 

[FrankDay]

I guess bold makes it better...

You haven't shown that your initial assumption of muscle efficiency to pedalling efficiency is accurate. Several people in this thread challenge your initial assumption.

Well, they have done so without a single fact. To challenge the assumption that there are losses between the muscle and the pedal requires one to assume that the cyclist pedaling coordination and motion involves zero losses. To a mechanical engineer such a notion is ludicrous. This is especially evident when we know measured efficiency of cyclists varies between 16 and 26%. Unless one believes muscle contractile efficiency be vary that much. No one experienced in this area believes this. Your argument is made out of emotion and ignorance.

If that initial assumptions is not correct, or is vastly overstated, then your subsequent discussion is less relevant or completely irrelevant, depending on how accurate your initial assumption was.

The initial assumption that there are losses is correct. The only questions are the magnitude of the losses, the source of the losses, and whether any of them can be recovered. The maximum possible cycling efficiency is set by the muscle contractile efficiency, whatever that is in the cyclist being measured. In most people there is a considerable drop between that number and what their actual cycling efficiency is. You (and, it seems, everyone else including the cycling researchers - notice how quiet Dr. Coggan and Dr. Martin are) seem to have zero clue as to how one might account for the entirety of the drop. It really is a fairly simple reverse engineering analysis if a researcher had the tools and wanted to do so. But, none have. Until then we are forced to discuss theoretical results from the data we do have. The only reasonable solution to the measured drop we see it the pedaling dynamic contributes a large portion of the loss.