The pedaling technique thread

[sciguy]

Hugh, the net power is, of course, positive. However, it would be more positive if the cyclist were not working against himself after 3 o'clock. It is a pretty simple analysis.

Care to expand on how he is doing that?

Do you find it a little odd that non-muscular power is negative at 3 o'clock?

Are we looking at the same diagram?

One more thing. If you were to eliminate the gravity component and graph the work done around the circle by Peter Vabrousek (I am sure you remember) I posted earlier, that net work line would be pretty much a straight line showing net work was being divided up around the circle pretty well. If you can increase the low parts of the graph why don't you want to since the power generated is the average power around the circle, not the peak. I might add that this rider is about at the same power as Petr in his graph but they have totally different pedaling patterns. I think I will superimpose Petr's pattern on this graph then we can compare as to which looks "better" to the eye test.[/QUOTE]

Frank I can't fathom why you seem to be so hung up on the "perfect circle" being important to efficient pedaling for most cyclists. I would grant that for mountain bikers a more even force application can be a real advantage when climbing poor traction sections of trail.

Hugh

 

[FrankDay]

Better still, look at the same data after correcting for the non-muscular components (which proves you wrong):

LOL. My friend, there is a negative muscular component just after 3 and at 12. It is small but it is negative. But, aside from that, those muscular components are not very tangential. Look where the muscular forces are greatest, from 3 to 5. The angle of the force vector is offset from the angle of the pedal motion by 20-45?. So, the rider is only getting 70-90% of the muscular effort being transferred to propel the bike. If his coordination were a little different he could generate the same power for less effort or more power for the same effort. Further this rider is doing essentially zero work at both the bottom and top of the stroke. What is wrong with his hamstrings and why is he delaying his quad firing? There is so much room for improvement here this, to me, constitutes an awful technique, even though there is very little active resistance. This rider is working about 40% of the circle when he could be doing so much better. (see the Petr Vabrousek illustration)

 

[sciguy]

Come on Hugh. Look at the illustrated pedal force diagram (which represents typical pedaling pattern of most non-PowerCranks trained cyclists) specifically between 3 and 4:30 o'clock.

The pedal is moving down and to the left but the pedal forces are down and to the right. Those "to the right" forces can only come from active contraction of the quads while the pedal is in this position so we have a pedal moving to the left and an active application of force to the right which definitely constitutes "actively working against themselves" wouldn't you agree?

Frank, were you sick during the unit on vectors in high school physics let alone your engineering physics courses?

Hugh

 

[FrankDay]

Are we looking at the same diagram?

Ooops. 1 o'clock, Just after TDC

Frank I can't fathom why you seem to be so hung up on the "perfect circle" being important to efficient pedaling for most cyclists. I would grant that for mountain bikers a more even force application can be a real advantage when climbing poor traction sections of trail.

Hugh

While an even application of power is useful for mountain bikers for road cyclists I simply don't see why why don't want to get power out of every muscle they can. Why make half the muscles do all the work when you can make all the muscles do all the work?

 

[FrankDay]

So, let's take this illustration and talk a little bit about it.

A US National Team member so must be pretty good. Why don't we discuss what to do with this information.

I suspect that a coach like Fergie wouldn't even gather it because there is nothing to be gained here.

I suspect that the typical coach would look at this (like Dr. Coggan did) and say, I don't see any negatives here so keep on doing what got you here.

If I were his coach I would say, WOW, lots to work on. Let's get to work.

What would you say?

 

[JamesCun]

Franks latest argument: It's just gotta be so, come on guys, you have to believe me on this, you just have to...

 

[JayKosta]

Non muscular power is a fixed number for each athlete. It is the gravity acting on the leg.

---------------
I don't understand - I'll have to think about it some more!
I was thinking that 'non muscular power' was produced by the combination of the circular momentum of the foot & pedal, and from gravity that WAS NOT countered by some amount of upward muscle contraction.

I certainly agree that the gravity FORCE is present - but even that is changing relative to the up/down acceleration of the leg/foot/pedal as it goes through a full rotation.

In any event - achieving more 'net muscular power' would increase the overall 'pedal power'.

Jay Kosta
Endwell NY USA

 

[sciguy]

---------------
I don't understand - I'll have to think about it some more!

Jay, here is Jim Martin's whole post. Perhaps it will help with your understanding

Hi Hugh:
Looks like I might be clear to post so I can try make a few contributions now. I know I'm years late to this party but perhaps I can make a few helpful points.

As many posters have suggested, force or power delivered to the pedal at any instant represents a combination of muscular and non muscular terms. In the figure below you will see data from a recent study in my lab. These are average data from 10 cyclists and the general pattern is typical of biomechanics reported in many publications.

The black squares show the total power being delivered to the right pedal at 250 watts (overall) and 80 rpm. There is negative power (which is typical of almost all cyclists) delivered to the pedal in the flexion phase. This of course is the basis for so much discussion about pedaling technique. The blue squares show the non muscular contribution to power which arises from gravity and from acceleration (linear and angular) of the limb segments. This term is positive generally as the limb extends and negative as the limb flexes. This data only represents one side so keep in mind that the other limb is 180 degrees out of phase which keeps the non muscular power term nearer to zero throughout the cycle. That is, the two limbs generally balance one another. The red squares show muscular power contribution. In other words, the red represents what the cyclist actively "does". Note that muscular power is always positive and this is typical of most cyclists we see in our lab. Very few actually produce negative (counterproductive) power with muscular actions even when highly fatigued. So, muscular power during leg flexion is, in fact, positive throughout the cycle. Its just not usually high enough to overcome the non muscular demand. As I mentioned above, the other leg is extending during this phase so the net non muscular power from both pedals is nearer to zero throughout the cycle and averages to zero for a complete revolution during steady state cycling. Consequently, there is nothing in a typical pedaling technique to "fix" with additional pulling up to "improve" technique. I hope this sheds some light on the topic.

I am in a busy time with courses under way and a large grant submission due next month so I will not be able to participate in this discussion as much as some of you. I will try to drop in from time to time and help clarify. However, I will not be able to engage in tit for tat arguments.
Cheers,
Jim

 

[FrankDay]

---------------
I don't understand - I'll have to think about it some more!
I was thinking that 'non muscular power' was produced by the combination of the circular momentum of the foot & pedal, and from gravity that WAS NOT countered by some amount of upward muscle contraction.

I certainly agree that the gravity FORCE is present - but even that is changing relative to the up/down acceleration of the leg/foot/pedal as it goes through a full rotation.

In any event - achieving more 'net muscular power' would increase the overall 'pedal power'.

Jay Kosta
Endwell NY USA

Non muscular force is not fixed for each athlete. It depends upon a lot of things and can change. There are two components to non-muscular force that is generated. Of course, one is the gravity component. That depends upon the mass of the leg parts and the orientation of the parts in relation to the pedal. All of the forces have to end up supporting the leg. It starts to get difficult once the pedal starts moving because this causes an acceleration force into the equation. The foot moves in a circular direction so the acceleration is always radial for the foot mass causing the pedal to see an outward force. The lower leg moves in an oval so its resultant force is sort of like the foots but a little elongated. The thigh pumps up and down, It is always accelerating but either up and down, no forward and aft component. This is why the non-muscular force down is smaller from 1-3 than from 3 to 6, because the thigh is being accelerated down from 1-3, reducing the gravity component but being decelerated from 3-6, increasing the gravity component. That is why you can see a non-muscular force up at TDC even though one would expect gravity to cause the force there to be down. The size of all of these acceleration forces depends upon the mass of the various body parts, their various lengths, the crank length, and the cadence. Two of these are not fixed in any athlete so that is why these forces are not fixed for any athlete.

These non-muscular forces should always sum out to zero which is why it is a fools errand to waste energy trying to overcome these to get the total vector to be tangential. No wonder those studies that look at "force effectiveness" find no correlation between force effectiveness and efficiency. It is these forces and their variability that will make interpretation of the Pioneer system difficult.

 

[JamesCun]

Non muscular force is not fixed for each athlete. It depends upon a lot of things and can change. There are two components to non-muscular force that is generated. Of course, one is the gravity component. That depends upon the mass of the leg parts and the orientation of the parts in relation to the pedal. All of the forces have to end up supporting the leg. It starts to get difficult once the pedal starts moving because this causes an acceleration force into the equation. The foot moves in a circular direction so the acceleration is always radial for the foot mass causing the pedal to see an outward force. The lower leg moves in an oval so its resultant force is sort of like the foots but a little elongated. The thigh pumps up and down, It is always accelerating but either up and down, no forward and aft component. This is why the non-muscular force down is smaller from 1-3 than from 3 to 6, because the thigh is being accelerated down from 1-3, reducing the gravity component but being decelerated from 3-6, increasing the gravity component. That is why you can see a non-muscular force up at TDC even though one would expect gravity to cause the force there to be down. The size of all of these acceleration forces depends upon the mass of the various body parts, their various lengths, the crank length, and the cadence. Two of these are not fixed in any athlete so that is why these forces are not fixed for any athlete.

These non-muscular forces should always sum out to zero which is why it is a fools errand to waste energy trying to overcome these to get the total vector to be tangential. No wonder those studies that look at "force effectiveness" find no correlation between force effectiveness and efficiency. It is these forces and their variability that will make interpretation of the Pioneer system difficult.

How much does the non muscular force change with different cadences? Most people ride in a range of 70-100 with a small portion in the 60-120 range at times.

 

[FrankDay]

How much does the non muscular force change with different cadences? Most people ride in a range of 70-100 with a small portion in the 60-120 range at times.

It will change with the square of the cadence. Take the thigh. The distance the knee moves is fixed by the crank length. If we increase the cadence not only will the knee end up moving faster but it will have less time to get up to speed. So, from 70 to 100 the non-muscular acceleration forces will be about doubled. 60 to 120 would result in a quadrupling of the acceleration forces.

 

[coapman]

If I were his coach I would say, WOW, lots to work on. Let's get to work.

What would you say?

Where do we start.

 

[FrankDay]

Jay, here is Jim Martin's whole post. Perhaps it will help with your understanding

Hi Hugh:
Looks like I might be clear to post so I can try make a few contributions now. I know I'm years late to this party but perhaps I can make a few helpful points.

As many posters have suggested, force or power delivered to the pedal at any instant represents a combination of muscular and non muscular terms. In the figure below you will see data from a recent study in my lab. These are average data from 10 cyclists and the general pattern is typical of biomechanics reported in many publications.

The black squares show the total power being delivered to the right pedal at 250 watts (overall) and 80 rpm. There is negative power (which is typical of almost all cyclists) delivered to the pedal in the flexion phase. This of course is the basis for so much discussion about pedaling technique. The blue squares show the non muscular contribution to power which arises from gravity and from acceleration (linear and angular) of the limb segments. This term is positive generally as the limb extends and negative as the limb flexes. This data only represents one side so keep in mind that the other limb is 180 degrees out of phase which keeps the non muscular power term nearer to zero throughout the cycle. That is, the two limbs generally balance one another. The red squares show muscular power contribution. In other words, the red represents what the cyclist actively "does". Note that muscular power is always positive and this is typical of most cyclists we see in our lab. Very few actually produce negative (counterproductive) power with muscular actions even when highly fatigued. So, muscular power during leg flexion is, in fact, positive throughout the cycle. Its just not usually high enough to overcome the non muscular demand. As I mentioned above, the other leg is extending during this phase so the net non muscular power from both pedals is nearer to zero throughout the cycle and averages to zero for a complete revolution during steady state cycling. Consequently, there is nothing in a typical pedaling technique to "fix" with additional pulling up to "improve" technique. I hope this sheds some light on the topic.

I am in a busy time with courses under way and a large grant submission due next month so I will not be able to participate in this discussion as much as some of you. I will try to drop in from time to time and help clarify. However, I will not be able to engage in tit for tat arguments.
Cheers,
Jim

So, I took this data and put them into a spreadsheet. I then added the data from that I collected from a 10 year PowerCranker and scaled it to to give the exact same power, making the assumption that the basic pedaling technique doesn't vary much with power. Using the additional assumption that the mass of the limbs of the two riders and cadence were the same I then subtracted the non-muscular work from both of these measured forces so we can compare the muscular work done using these two different pedaling techniques. This is what I got.

The tan line is the muscular work done around one revolution to achieve 123.6 watts using "ordinary" pedaling techique. The red line is the muscular work done around one revolution to achieve 123.6 watts using a "circular" pedaling technique. Discuss.

 

[coapman]

What was used to get these forces ?

 

[sciguy]

The tan line is the muscular work done around one revolution to achieve 123.6 watts using "ordinary" pedaling techique. The red line is the muscular work done around one revolution to achieve 123.6 watts using a "circular" pedaling technique. Discuss.

Quick questions.

Has the accuracy of the Icranks been validated by any accredited testing lab?

Where the Icranks Petr was on set to 140mms?

Do you have access to precise values of power way above and beyond is simple graphic?

It appears that you scaled the power of the left crank. How about doing the right one?

Was this data taken at an expo in front of you and a crowd of onlookers where being able to pedal circles would be important to Petr's feelings of self worth?

What do you feel that this proves or implies beyond Petr seems able to do it at a low wattage for at least short period of time?

I use to be able to balance a track bike for hours on end but it really doesn't really have any practical application.

Hugh

 

[JamesCun]

Isn't there also a problem of scaling the power when we are discussing the non-muscular component? The icranks would include the non-muscular in the measurement, and frank then removes a number that is potentially much different. I would think that could drastically skew the results, so many assumptions. Especially since he said the non-muscular power can double or halve within the range of normal cadences.

 

[sciguy]

What was used to get these forces ?

Noel,

They directly measure the pedal power using a set of force measuring pedals that Jim has so graciously offered to test your technique with.
The Net Muscular power and Non-Muscular power are calculated from knowledge of the crank length, foot/leg mass and cadence along with the measured Pedal Power.

Jim still looks forward to seeing you tested. He'd be glad to set up a test in the UK for you if the Brim Brother's don't have this ability.

Hugh

 

[FrankDay]

Quick questions.

Has the accuracy of the Icranks been validated by any accredited testing lab?

I don't know. I know the model they intend to ship has been tested and was extremely accurate. It really doesn't matter because as long as the output of the strain gauges is linear the pattern will be correct. And since we are scaling anyhow accuracy of the numbers is immaterial for this effort.

Where the Icranks Petr was on set to 140mms?

No, they were short as I remember (150 I believe) so the reported power is probably low but, again, the relative values should be correct.

Do you have access to precise values of power way above and beyond is simple graphic?

no. The latest iterations of the cranks is supposed to save the specific numbers but what I had didn't allow that.

It appears that you scaled the power of the left crank. How about doing the right one?

I thought I did the right but it really doesn't matter as they are so similar in shape (and I was guessing at a lot of the numbers and needing to get the two powers the same) I don't think the red curve would be a lot different.

Was this data taken at an expo in front of you and a crowd of onlookers where being able to pedal circles would be important to Petr's feelings of self worth?

This is surely one of the silliest questions you have ever asked me. Would Petr's self worth might be modified by whether he could pedal in "perfect circles" when being monitored by me? Or in front of a crowd. First, there was no crowd. All I can tell you is he just hopped on the bike and was riding at an easy clip. He couldn't see the screen to see what he was doing. I don't think he even knew I was recording it so I could show what he was doing. Anyhow, the same criticism could apply to the other rider who knew his pedal stroke was being analyzed.

What do you feel that this proves or implies beyond Petr seems able to do it at a low wattage for at least short period of time?

That it is actually possible to train people to pedal in almost perfect circles, distributing the work pretty equally around the circle. Other than that it proves nothing.

I use to be able to balance a track bike for hours on end but it really doesn't really have any practical application.

If you have any evidence that the pedaling technique demonstrated by Martin's rider is superior to Petr's technique I would love to see it. Petr is a pretty amazing rider. He doesn't win very many of the biggest races but he does a long distance race like an Ironman probably about 40 times a year and either wins or is in the top 10 is probably 75% of those. Don't you think it would be useful for someone like Dr. Martin to search out a few cyclists like Petr (there are plenty of them around) so he can truly compare the two techniques for efficiency, etc? Then we might be able to say something definitive. It is hard for me to imagine that the National Cyclist is pedaling optimally when he doesn't start contracting his quads until about 2 o'clock and his hamstrings are pretty much no existent when the pedal is moving back.

The question is whether it is better to use part of the circle or all of it. Evaluate the evidence then what you choose is up to you. I know which one I would choose.

 

[FrankDay]

Isn't there also a problem of scaling the power when we are discussing the non-muscular component? The icranks would include the non-muscular in the measurement, and frank then removes a number that is potentially much different. I would think that could drastically skew the results, so many assumptions. Especially since he said the non-muscular power can double or halve within the range of normal cadences.

Well, the screen shot said he was at a cadence of 83 when that data was taken. Unless the riders were substantially different the non-muscular forces should be reasonably close to being the same. Non-muscular forces at the same cadence would only vary in magnitude but the general shape should be the same and they always zero out so I think this is a reasonable comparison.

 

[FrankDay]

Noel,

They directly measure the pedal power using a set of force measuring pedals...

Not quite right. In most cases they indirectly measure the forces to the pedal using strain gauges. To calculate the power they also need to know the pedal speed and this is frequently done by measuring the cadence, knowing the crank length which gives them the circumference of the circle and an average pedal speed for that rotation, assuming the pedal speed is constant around the circle (not true but close enough for most of this work). From these two measurements they can then calculate the instantaneous power every time they have a data point.

 

[coapman]

Can you name a single other sport in which the degrees-of-freedom (of motion) are so restricted?

A good workman never blames his tools.

 

[FrankDay]

Can you name a single other sport in which the degrees-of-freedom (of motion) are so restricted?

A good workman never blames his tools.

Dr. Coggan is simply rationalizing his failure to address this issue. It is a ridiculous position to take. "Just because my feet are attached to pedals that restrict my foot to a circular motion changes things such that it doesn't matter which direction I push with my muscles as efficiency now won't change. Pedal moving forward? No problem, I can push down if I want to and no one will know and I will go just as fast." LOL

 

[FrankDay]

I guess I have to apologize to SciGuy for disparaging his post about muscle efficiency in which I thought the authors violated the laws of thermodynamics. They do not. However, this article has almost nothing to do with what we normally talk about. I am not through the entire article yet but it is clear they are looking at the efficiency of muscle contraction in the steady state, when all energy stores have been used up. This leads us into the dilemma of trying to put studies like this against the typical data we hear about. What is the muscle efficiency of the sprinter who is contracting his muscles maximally for about 10 seconds with almost no oxygen consumption (using mostly stored energy molecules and anerobic pathways)? It would seem near infinity (violating the laws of thermodynamics). Or, the efficiency of the typical lab test, which may last 20 minutes where stores are used but not exhausted? This paper explains why we slow down the longer the race lasts because muscle efficiency (as normally measured) will drop as energy stores are used up. But, it does not prevent us from looking at the energy efficiency of pedaling as measured in the laboratory where muscle efficiency is around 40% and cycling efficiency is 20%. Details matter folks. This study should be ignored for the purposes of this discussion even though it doesn't violate the laws of thermodynamics.

 

[coapman]

So, I took this data and put them into a spreadsheet. I then added the data from that I collected from a 10 year PowerCranker and scaled it to to give the exact same power, making the assumption that the basic pedaling technique doesn't vary much with power. Using the additional assumption that the mass of the limbs of the two riders and cadence were the same I then subtracted the non-muscular work from both of these measured forces so we can compare the muscular work done using these two different pedaling techniques. This is what I got.

The tan line is the muscular work done around one revolution to achieve 123.6 watts using "ordinary" pedaling techique. The red line is the muscular work done around one revolution to achieve 123.6 watts using a "circular" pedaling technique. Discuss.

It is claimed by most cycling experts and coaches that trying to improve power application by changing pedalling technique is a waste of training time because when real power is required a rider will revert back to his natural style of pedalling. For this reason to get a true picture of what different pedalling techniques are capable of, testing should be done at maximal power output. You would need a rider who has perfected both the circular and mashing techniques and get him to ride at max power output in the same gear with both techniques for one crank revolution analysis.

 

[FrankDay]

It is claimed by most cycling experts and coaches that trying to improve power application by changing pedalling technique is a waste of training time because when real power is required a rider will revert back to his natural style of pedalling.

They may claim that but they are simply rationalizing their decision to not try to coach pedaling technique as there is zero data to even suggest that those properly trained in a different technique would revert (asking someone to pedal in a different fashion or 6 weeks of training does not constitute proper training). I think the evidence is pretty strong that the basic pedaling style of any individual is pretty much the same at all different power levels. IMHO, if a rider is going to "revert" it would be due to an imbalance in the endurance capacity of the various muscle groups forcing a change in technique as the weakest group starts to fail. Such a failing would suggest that such a rider is not "properly trained" to me.

For this reason to get a true picture of what different pedalling techniques are capable of, testing should be done at maximal power output. You would need a rider who has perfected both the circular and mashing techniques and get him to ride at max power output in the same gear with both techniques for one crank revolution analysis.

No one individual can "perfect" both styles at the same time. They will either ride one way or another. What is needed is to test two groups of riders who have "perfected" two different styles, match them, then test them at a variety of power. This would be pretty easy to do by looking for riders with a long history with PowerCranks, confirming they ride similarly to what Petr demonstrated, then matching them to a "conventionally trained" rider. It would be even better if muscle biopsies could be obtained for matching purposes also. This would not be a terribly difficult study to conduct as long as there were enough "properly trained" "PowerCrankers" in the geographical area of the researcher to get enough subjects for a good comparison.

Many people say pedaling technique doesn't matter based on the studies thus far. I think that is simply because the difference in technique between conventionally trained riders is so small (as are the groups being tested) that it is not possible to uncover any differences that might be present in view of both the small difference that is present and small numbers being analyzed. However, I think it is clear there is a substantial difference in the pedaling technique between the conventional rider and a circular pedaler that if enough cyclists can be accumulated that actually pedal the two different styles then it should be possible to demonstrate any difference in efficiency or not related to pedaling style. My guess is 5-10 riders using each style should be enough to clearly demonstrate that pedaling technique clearly makes a difference.