The pedaling technique thread

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In the Leirdahl study, what is 'dead center size' ?
It seems to be the ratio (%) of
'power at 6/12 o'clock'
to
'what?)

Is DC power being compared to 'average power', 'maximum instantaneous power', or something else?

I couldn't find a 'full text' of the study.
-------------------------------------------------------

In the Edwards study "Whole-body efficiency is negatively correlated with minimum torque per duty cycle in trained cyclists", the abstract says -

"The most notable results were as follows: gross efficiency (r = -0.72, P < 0.05 at 250 W) was inversely correlated with the ratio of minimum to peak torque, particularly at higher work rates."

To me, the mention of inverse correlation seems to say that as the torque RATIO gets larger (greater minimum torque), that GROSS EFFICIENCY becomes smaller.
Am I misunderstanding the 'words' in the abstract, or is there something else going on?

Jay Kosta
Endwell NY USA
 
Sep 23, 2010
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JayKosta said:
In the Leirdahl study, what is 'dead center size' ?
It seems to be the ratio (%) of
'power at 6/12 o'clock'
to
'what?)

Is DC power being compared to 'average power', 'maximum instantaneous power', or something else?

I couldn't find a 'full text' of the study.
-------------------------------------------------------

In the Edwards study "Whole-body efficiency is negatively correlated with minimum torque per duty cycle in trained cyclists", the abstract says -

"The most notable results were as follows: gross efficiency (r = -0.72, P < 0.05 at 250 W) was inversely correlated with the ratio of minimum to peak torque, particularly at higher work rates."

To me, the mention of inverse correlation seems to say that as the torque RATIO gets larger (greater minimum torque), that GROSS EFFICIENCY becomes smaller.
Am I misunderstanding the 'words' in the abstract, or is there something else going on?

Jay Kosta
Endwell NY USA
Good pick up. I wondered if anyone would call me on this. I can't remember the definition of DC size but I think it had to do with the relative size of the 6-12 combined DC vector force to the average force of the stroke.

I couldn't find the full text of the later study to see what they really meant. On the face of it the term inverse suggests these two studies have contradictory results to me (which sometimes happens in science) but I suspect this is probably a definition issue. (Edit: Or, it could be an issue with study design. Did they do what Martin did when he asked people to pedal in a fashion that was different than their normal technique and notice a drop in efficiency? We need more information to sort this out.)

What is interesting to me is both studies conclude that what is going on at the top and bottom of the stroke affect pedaling economy? It would be nice if someone who has access to the full text could confirm what they really found so we can know if these confirm or contradict each other. Either way, more work probably needs to be done to further confirm or to explain the difference.
 
Mar 10, 2009
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FrankDay said:
Good pick up. I wondered if anyone would call me on this. I can't remember the definition of DC size but I think it had to do with the relative size of the 6-12 combined DC vector force to the average force of the stroke.
How man degrees in the pedal stroke ?
 
JayKosta said:
In the Leirdahl study, what is 'dead center size' ?
It seems to be the ratio (%) of
'power at 6/12 o'clock'
to
'what?)

Is DC power being compared to 'average power', 'maximum instantaneous power', or something else?

Jay Kosta
Endwell NY USA
Jay someone else provided the excerpt below when I asked that question a while back.

Recently, Leirdal and Ettema (2010) introduced a new pedalling technique parameter, which described the dead centre (DC) and was defined as the minimum power divided by the average power during the pedal stroke.
 
Mar 10, 2009
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sciguy said:
Jay someone else provided the excerpt below when I asked that question a while back.

Recently, Leirdal and Ettema (2010) introduced a new pedalling technique parameter, which described the dead centre (DC) and was defined as the minimum power divided by the average power during the pedal stroke.
If the pedal stroke includes all 360 degrees the minimum power application will not occur at 12 or 6 o'c. A 180 deg pedal stroke that includes max and min torque will have min torque at 12 or 6.
 
coapman said:
If the pedal stroke includes all 360 degrees the minimum power application will not occur at 12 or 6 o'c. A 180 deg pedal stroke that includes max and min torque will have min torque at 12 or 6.
coapman,

Do you see mention of 12 of 6 in the definition? I only see minimum power. It was Frank Day who added the 12 and 6 as his interpretation to the definition.

Hugh
 
Mar 10, 2009
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sciguy said:
coapman,

Do you see mention of 12 of 6 in the definition? I only see minimum power. It was Frank Day who added the 12 and 6 as his interpretation to the definition.

Hugh

Where does this "minimum power" power occur ?
 
coapman said:
Where does this "minimum power" power occur ?
It might occur anywhere within a specific individual's particular cycling stroke. For many it might well be 12ish and 6ish as we have not mastered your wonderful technique yet;)

Hugh
 
coapman said:
Where does this "minimum power" power occur ?
=========================================
For the purpose of THAT study - it probably doesn't matter WHERE the minimum power happens, only that there is some repeating location in the 360degree pedal stroke where the power is least.

I think it needs to be highlighted that the study is primarily concerned with physiological 'efficiency', and doesn't get into actual cycling 'performance'.

I think that the study shows that 'efficiency' (based on O2 consumption) improves as the power output becomes more 'constant' during a full-rotation pedal cycle. But there are still questions about muscle endurance and fatigue; can the 'high efficiency' pedaling technique be performed for a long duration?

Jay Kosta
Endwell NY USA
 
Mar 10, 2009
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JayKosta said:
=========================================
For the purpose of THAT study - it probably doesn't matter WHERE the minimum power happens, only that there is some repeating location in the 360degree pedal stroke where the power is least.

I think it needs to be highlighted that the study is primarily concerned with physiological 'efficiency', and doesn't get into actual cycling 'performance'.

I think that the study shows that 'efficiency' (based on O2 consumption) improves as the power output becomes more 'constant' during a full-rotation pedal cycle. But there are still questions about muscle endurance and fatigue; can the 'high efficiency' pedaling technique be performed for a long duration?

Jay Kosta
Endwell NY USA

This is just another way of telling people what is already known, your pedaling is more efficient if you unweight the rising pedal.
 
Mar 10, 2009
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My second powermeter question which was deleted, was as follows. How many measurements are taken over the crank revolution by icranks, axiscranks claims 200 per second.
 
Sep 23, 2010
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coapman said:
My second powermeter question which was deleted, was as follows. How many measurements are taken over the crank revolution by icranks, axiscranks claims 200 per second.
Why is this question here, this should be in the power meter thread. Anyhow, lots. I was under the impression it was thousands but I don't know for sure.
 
Apr 21, 2009
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FrankDay said:
Why is this question here, this should be in the power meter thread. Anyhow, lots. I was under the impression it was thousands but I don't know for sure.
It's pretty simple. It belongs here because Noel isn't interested in power, just his pedalling technique.
 
Mar 10, 2009
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CoachFergie said:
It's pretty simple. It belongs here because Noel isn't interested in power, just his pedalling technique.
It's here because the adm. could not distinguish PM's from pedaling equipment. If I was seriously interested in powermeter training I would be a member of the new " Wattage " forum. Which is more important, the generation of pedal power or the powermeter. You may not realize it but you are using the same instinctive technique of a young child after his first day of pedaling on his bike or trike. The improved powermeters which can give accurate measurements of crank torque around the pedaling circle can increase power output but only when their use is combined with the science of improving pedaling technique.
 
Apr 21, 2009
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coapman said:
It's here because the adm. could not distinguish PM's from pedaling equipment. If I was seriously interested in powermeter training I would be a member of the new " Wattage " forum. Which is more important, the generation of pedal power or the powermeter. You may not realize it but you are using the same instinctive technique of a young child after his first day of pedaling on his bike or trike. The improved powermeters which can give accurate measurements of crank torque around the pedaling circle can increase power output but only when their use is combined with the science of improving pedaling technique.
Pedalling equipment?

You mean shoes, cranks and pedals.

Pedal Power or Powermeter?

Haven't seen an independent validation of AXIS, iCrank, Brim Bros, Garmin Vector, Wattbike, Spinscan that they actually measure anything of note and if the measurement they make is accurate.

Improved power meter?

Off topic for this thread but at the end of the day the overall power measured is what a rider is trying to improve. If you took up Jim Martin's offer to be tested using force measuring pedals the main variable of interest would still be whether you could produce more power for a particular duration.

Science of pedalling technique?

Nothing has been published yet that would suggest there is any pedalling technique that is superior to what we instinctively do. Being taught or instructed to pull up, use uncoupled cranks, elliptical chainrings, toe clips, cleated shoes and different crank lengths have never been shown to significantly increase power or improve efficiency.
 
CoachFergie said:
...
but at the end of the day the overall power measured is what a rider is trying to improve.
...
====================================

I don't think that improved 'overall power' is the total goal.

Some amount of power is wasted if pedal technique causes cyclic variation in speed so that the rider is required to use extra power to ACCELERATE on each pedal rotation. The power needed to maintain a constant speed (of both the bike and the pedals) is less than if there is cyclic acceleration and deceleration.
The sector of a pedal rotation that produces most power is where acceleration is happening, and the low power sector is where deceleration happens.

From a 'mechanical engineering' viewpoint, avoiding unneeded acceleration and deceleration should increase efficiency. The question regarding cycling is whether our physiology allows riders to see similar efficiency gains AND high performance

The use of devices that measure and show how a pedal stroke varies thru a rotation can be useful in comparing pedal techniques that develop the same overall power.

Jay Kosta
Endwell NY USA
 
Mar 10, 2009
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CoachFergie said:
Pedalling equipment?

You mean shoes, cranks and pedals.

Pedal Power or Powermeter?

Haven't seen an independent validation of AXIS, iCrank, Brim Bros, Garmin Vector, Wattbike, Spinscan that they actually measure anything of note and if the measurement they make is accurate.

Improved power meter?

Off topic for this thread but at the end of the day the overall power measured is what a rider is trying to improve. If you took up Jim Martin's offer to be tested using force measuring pedals the main variable of interest would still be whether you could produce more power for a particular duration.

Science of pedalling technique?

Nothing has been published yet that would suggest there is any pedalling technique that is superior to what we instinctively do. Being taught or instructed to pull up, use uncoupled cranks, elliptical chainrings, toe clips, cleated shoes and different crank lengths have never been shown to significantly increase power or improve efficiency.

How could anything be published when only myself and possibly Anquetil were the only two to use this semi circular technique. The engineers behind the AXIS CRANK PM are in agreement with me on one important fact, there is only one dead spot in pedaling and it's at the 60 degrees (approx.) around 12 o'c. But what they are not aware of is that maximal torque can be applied there. The dead spot sector occurs when the muscles of both legs are effectively idling, put one leg to work there and that dead spot no longer exists, you have continuous effective torque application throughout the 360 degree chain ring revolution. The best that can be done with the 180 degree recovery stroke is to neutralize it by unweighting which does not interfere with the leg muscles recovery time.
 
Apr 21, 2009
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coapman said:
How could anything be published when only myself and possibly Anquetil were the only two to use this semi circular technique. The engineers behind the AXIS CRANK PM are in agreement with me on one important fact, there is only one dead spot in pedaling and it's at the 60 degrees (approx.) around 12 o'c. But what they are not aware of is that maximal torque can be applied there. The dead spot sector occurs when the muscles of both legs are effectively idling, put one leg to work there and that dead spot no longer exists, you have continuous effective torque application throughout the 360 degree chain ring revolution. The best that can be done with the 180 degree recovery stroke is to neutralize it by unweighting which does not interfere with the leg muscles recovery time.
Let us know when you have data to back up your observations.

Obree talks about kicking a soccer ball as you pedal across the top of the stroke. Joe Friel talks about trying to throw your knee over the handlebars to try and do the same thing. No data to support the efficacy of this.

We await the validation of both the AXIS and iCrank's ability to accurately measure anything.
 
Apr 21, 2009
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JayKosta said:
I don't think that improved 'overall power' is the total goal.
Don't recall saying it was the total goal. Based off testing I advised a girl I coach she would be able to ride 54sec faster in a 15km Time Trial than last year. In the regional champs on the weekend she went 2:30min faster. More to the total goal than power.

Some amount of power is wasted if pedal technique causes cyclic variation in speed so that the rider is required to use extra power to ACCELERATE on each pedal rotation. The power needed to maintain a constant speed (of both the bike and the pedals) is less than if there is cyclic acceleration and deceleration.
The sector of a pedal rotation that produces most power is where acceleration is happening, and the low power sector is where deceleration happens.

From a 'mechanical engineering' viewpoint, avoiding unneeded acceleration and deceleration should increase efficiency. The question regarding cycling is whether our physiology allows riders to see similar efficiency gains AND high performance
All probably true but the question is one of importance. As we saw looking at crank length data the difference for the tallest or shortest of riders changing from a 170mm crank was 0.5% at best. A very trivial amount.

The use of devices that measure and show how a pedal stroke varies thru a rotation can be useful in comparing pedal techniques that develop the same overall power.
There is sufficient research showing that attempts to change pedalling technique don't make a significant improvement in either power or efficiency. In terms of improving performance it's a dead end.

The big gains in performance come from specific training, choosing parents wisely, macronutition, and refining the training-recovery process.
 
Mar 10, 2009
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CoachFergie said:
.



All probably true but the question is one of importance. As we saw looking at crank length data the difference for the tallest or shortest of riders changing from a 170mm crank was 0.5% at best. A very trivial amount.



There is sufficient research showing that attempts to change pedalling technique don't make a significant improvement in either power or efficiency. In terms of improving performance it's a dead end.

The big gains in performance come from specific training, choosing parents wisely, macronutition, and refining the training-recovery process.

What has crank length got to do with acceleration and deceleration during the pedaling rotation. In all attempts to change technique the same basic instinctive technique was used, so how could there be an improvement.
 
Apr 21, 2009
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coapman said:
What has crank length got to do with acceleration and deceleration during the pedaling rotation. In all attempts to change technique the same basic instinctive technique was used, so how could there be an improvement
A claim was made that changing crank length would lead to an increase in power and an improvement in efficiency. Neither claim has been backed up with evidence.

Several studies that have changed the way we apply power around the pedal stroke and none so far have shown this to improve power and one that has shown an improvement in efficiency has not been shown in three subsequent studies that replicated the original
 
Apr 21, 2009
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Prob more a pedalling technique question.

Krebs cycle said:
So I can assure you, the science WILL be done! In the meantime, I believe there is enough evidence around to suggest that muscle recruitment patterns can affect performance....

http://www.ncbi.nlm.nih.gov/pubmed/22089483

http://www.ncbi.nlm.nih.gov/pubmed/20086134

http://www.ncbi.nlm.nih.gov/pubmed/17258470
My thoughts and just reading the abstracts is that these studies suggest the more you do something the more efficient you become at it. Same as Coyle in his case study on Lance. In his revision suggesting that the drugs facilitated recovery and allowed a higher training volume and this lead to the change in efficiency.
 
Sep 23, 2010
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CoachFergie said:
My thoughts and just reading the abstracts is that these studies suggest the more you do something the more efficient you become at it. Same as Coyle in his case study on Lance. In his revision suggesting that the drugs facilitated recovery and allowed a higher training volume and this lead to the change in efficiency.
Yes, the more one does something the better they seem to get at it. Works for playing the piano, doing surgery, flying airplanes, essentially everything. We have all heard of the 10,000 hour rule of thumb. The question here, in the pedaling technique thread, is whether there are better or lesser pedaling techniques and whether it is possible or desirable to try to change any technique that people have been using for years and are, presumably, pretty good at that technique to a different technique that is thought to be more desirable?

Anyhow, did get a recent anecdotal report that might suggest that technique does, in fact, matter and that improvement does continue with more and more time.
 
CoachFergie said:
Prob more a pedalling technique question.


My thoughts and just reading the abstracts is that these studies suggest the more you do something the more efficient you become at it. Same as Coyle in his case study on Lance. In his revision suggesting that the drugs facilitated recovery and allowed a higher training volume and this lead to the change in efficiency.
Thanks. I didn't want to take the other thread too far off topic so I tried to address your concerns about the validity of the ergometer over there. (what I didn't say however is that there are a couple of dynamic calibration rigs elsewhere in Australia that will probably be used to do some checking. They have one and the Axis ergo at the AIS in Canberra).

On the subject of pedalling technique and efficiency its not an area I have spent much time reading, but (since it's my job to read scientific research) I just spent the last 20min having a look. What I found was a bit of a mixed bag. Certainly there is a lack of evidence showing that efficiency is improved with a "pulling up" technique, however the BIG thing that is missing is a training study. Acutely changing technique would likely result in poorer muscular coordination, which may explain why efficiency goes down when cyclists consciously alter their pedalling technique to anything other than "preferred".

What happens if a pedalling technique that minimises negative power is trained for weeks or months?
 

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