The Powercrank Thread

[sciguy]

cool but it would be even better if winter showed up as I doubt Martin truly understands this stuff. It is mechanics. If he hasn't taken a statics or dynamics course in engineering school he may not get it. The forces will always balance. The question is whether contracting a muscle at any particular point helps or hurts what one is trying to accomplish.

Before you get too far up on that high horse you should know that Jim has a BS in Mechanical Engineering from University of Texas at Austin and worked for years as a Registered Professional Engineer before returning to grad school in exercise science. His statics and dynamics courses were taught using the classic Pletta and Frederick text.

His training in this area in all likelihood far exceeds yours. But you are the one that was in the Navy so that's on your side.

Hugh

 

[FrankDay]

So can I take that as an official apology?

It goes to the usefulness of discussions such as this as it can help people see errors in their thinking by hearing alternative views, at least to those willing to look introspectively and admit they made an error, which I like to think describes me but doesn't seem to describe everyone here. Anyhow, the question remains as to whether it is smart to be contracting the quad beyond 3. I still hold it is not. But, it you can make a cogent argument my mind can be changed.

 

[FrankDay]

Before you get too far up on that high horse you should know that Jim has a BS in Mechanical Engineering from University of Texas at Austin and worked for years as a Registered Professional Engineer before returning to grad school in exercise science. His statics and dynamics courses were taught using the classic Pletta and Frederick text.

His training in this area in all likelihood far exceeds yours. But you are the one that was in the Navy so that's on your side.

Hugh

Cool. Be a lot better than trying to have this discussion with elapid. As I kept telling him an engineer should be able to understand this stuff. If I have thought about this incorrectly they should be able to correct my thinking in a manner that makes sense to me. It is partly why I put these thoughts out in forums like this to see if I have made a critical error in thinking. Rarely, am I shown to be in error. We will see what happens if any bother to actually show up.

 

[coapman]

Anyhow, the question remains as to whether it is smart to be contracting the quad beyond 3. I still hold it is not.

One of the negative effects of using PC's, they teach you to ignore the down stroke. You believe it makes more sense to try and use almost powerless muscles to pull up between 9 - 11 o'c than to use your most powerful muscles pushing down with reducing tangential effect between 3 - 5 o'c

 

[JayKosta]

momentum is a product of pedal speed. Muscle contraction has no influence on momentum except how it influences pedal speed, which for a single rotation at power is a tiny one.

==================
That may be true for a complete pedal rotation.
But specifically at the 3 o'clock position, I think that the downward momentum of the entire foot. lower leg, and some portion of the upper leg (and also gravity) can't be ignored. My guess is that the momentum at 3 helps to 'smooth' the transition of muscle use from the quads to the glutes so that pedal speed is kept relatively constant.

This might be part of what you mentioned earlier about things not being as simple as they first appear.

Jay Kosta
Endwell NY USA

 

[FrankDay]

==================
That may be true for a complete pedal rotation.
But specifically at the 3 o'clock position, I think that the downward momentum of the entire foot. lower leg, and some portion of the upper leg (and also gravity) can't be ignored. My guess is that the momentum at 3 helps to 'smooth' the transition of muscle use from the quads to the glutes so that pedal speed is kept relatively constant.

This might be part of what you mentioned earlier about things not being as simple as they first appear.

Jay Kosta
Endwell NY USA

the major "momentum" problem in pedaling deals with the thighs. They are big, heavy, and each one goes from max speed to zero speed back to max speed twice each rotation. So, it is true the momentum there can help a tiny bit wit power production when slowing but the need to speed it back up robs from the power production. The lower legs are lighter and moves in an oval so this is much less an issue and the feet move in a circle so momentum for them is essentially constant.

It is a complicating issue for a full analysis but can be essentially ignored for our purposes.

 

[FrankDay]

Determining optimal pedaling technique is a very difficult problem to solve. Here are just a few of the issues

1. The leverage of each joint varies with the joint angle
2. The contractile efficiency of muscle varies with muscle length, which is determined by joint position.
3. The applied pedal force and direction is determined by the combined effects of all the muscles plus a gravitational/inertial component. Subtract the gravitational/inertial component and one can get an overall sense of the muscular effectiveness of the current coordination.
4. Any give muscle should not be contracting for more than 50% of the pedaling cycle (they do need time to recover to get ready for the next effort). The longer the effort the more recovery time each muscle needs.

The above all come into play in evaluating, say, the use of the quads. The quads have the potential to add driving torque from anywhere between 10:30 to about 5:30. This is more than 50% of the cycle so is clearly unsustainable. If we include a delay for initiating contraction and for relaxation to occur the best we can hope for under a high power situation (sprinting) would be 45% of the cycle. For an endurance situation maybe 40% of the cycle. So, then, it seems we should be looking for the most effective 40-45% of the cycle where the quads are best used taking the above joint and muscle considerations into the analysis. It is this consideration that causes me to think that it is better to be using the quads coming over the top than pushing well past 3 o'clock.

The same analysis could be done for each muscle after which an understanding of the theoretical best pedaling pattern would be known, at least using the assumptions of the model. This sounds like a good exercise for someone interested in exercise physiology and skilled at computer modeling. Then, the problem becomes training the technique and validating the model.

I hope some real experts come here and discuss these issues. I am not hopeful though as my experience suggests they don't like exposing what they don't know.

 

[sciguy]

I hope some real experts come here and discuss these issues. I am not hopeful though as my experience suggests they don't like exposing what they don't know.

Well you're never shy about exposing what you don't know Jim Martin just signed up for the forum yesterday and is still awaiting moderator approval before being able to post. It will be really refreshing to have someone on board who actually studies cycling based topics as apposed to just making stuff up in order to attempt to create a niche for a product they sell.

Hugh

 

[Bio_McGeek]

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

 

[coapman]

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

I take it that by force/power you mean crank torque. What I find interesting is how muscular power peaks before 3 o'c and non muscular power peaks after 3 o'c.

 

[JayKosta]

...
Consequently, there is nothing in a typical pedaling technique to "fix" with additional pulling up to "improve" technique.
...

====================================
I doubt that the above is the same as saying -
"No additional power can be generated with additional pulling up".

In other words (mine), the basic technique itself (as shown in the graph) is good, and training all, or some areas of the technique (perhaps pulling up), can result in (edit out for clarity: better overall results) MORE OVERALL POWER.

Jay Kosta
Endwell NY USA

 

[coapman]

====================================
I doubt that the above is the same as saying -
"No additional power can be generated with additional pulling up".

In other words (mine), the basic technique itself (as shown in the graph) is good, and training all, or some areas of the technique (perhaps pulling up), can result in better overall results.

Jay Kosta
Endwell NY USA

It is the same. Frank should take note of the effectiveness of applying muscular power after 3 o'c.

 

[JayKosta]

...
In other words (mine), the basic technique itself (as shown in the graph) is good, and training all, or some areas of the technique (perhaps pulling up), can result in (edit out for clarity: better overall results) MORE OVERALL POWER.

===============================
About 'training' - the graph shows high power being produced from about 30 degrees to 120 degrees, and I think most would agree that current training techniques are successful for the muscles used in that segment.

So an obvious question is whether current training techniques are also successful in developing the muscle usage in the 120-360-30 degree section. Does current training attempt to improve power in this section?
If not, what are the reasons?

Jay Kosta
Endwell NY USA

 

[CoachFergie]

So an obvious question is whether current training techniques are also successful in developing the muscle usage in the 120-360-30 degree section. Does current training attempt to improve power in this section?
If not, what are the reasons?

Seriously?

Go back and look at every study that has a control group at the start of this thread and you will have your answer.

SPECIFICITY!!!

Train how you intend to race. All else is training for training's sake!

 

[FrankDay]

I take it that by force/power you mean crank torque. What I find interesting is how muscular power peaks before 3 o'c and non muscular power peaks after 3 o'c.

Muscular power probably peaks before 3 because it requires muscle power to increase the thigh velocity to keep up with the pedal speed. Non-muscular power peaks after 3 because some of that effort putting momentum into the thigh is recovered as power as the thigh is slowed as the pedal changes directions from down to backwards. Notice the similar effect on the backstroke.

 

[FrankDay]

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

Thanks for the graph and the power analysis breakdown. At least we can now put to bed that cyclists don't pull up on the backstroke. Everyone does, it is simply a matter of the degree to which they do it.

That having been said, I must say that coming from someone with a background in mechanical engineering that your analysis was about as lame as I could possibly imagine. There is a lot in that data and it is simply silly to conclude that because muscular power is positive (even if barely so, check out 11 o'clock) around the entire circle that there is "nothing to fix". There is simply nothing in that data to suggest that everything is "perfect" because all you have done is measure what people are currently doing. Why are the muscles doing so much less work coming across the top compared to the bottom? Are the quads that much smaller than the hamstrings? Is it really not possible for the lifting muscles to not be trained to do more in relation to the "pushing" muscles? Before one can say there is nothing to fix one needs to know more about how the different muscles are being used and what the potential of those muscles are.

Edit: somehow my edit was put in the wrong place (brain fart I suppose). I will redo. This is a thread regarding PowerCranks, cranks designed to train the athlete to improve the portions of the stroke other than the pushing portion. From a mechanical engineering perspective a further question would be why it wouldn't be a good idea, if possible, to train the "pulling" phase muscles to fully unweight (or more) to bring that muscular power to be closer to that of the "pushing" phase, if that were possible? Do you see an advantage coming to the athlete if the weaker parts of the stroke can be brought closer to the stronger part of the stroke through training? Isn't an extra watt on the backstroke (or the top or the bottom or all of those) the same as an extra watt on the downstroke? Or, do you see training as a zero sum game. If so, why?

Anyhow, welcome. Stand by to defend your views.

 

[CoachFergie]

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.

Tidies things up rather nicely. Thanks for bringing your expertise to the discussion.

 

[FrankDay]

It is the same. Frank should take note of the effectiveness of applying muscular power after 3 o'c.

??? What should I note? I see muscular power dropping off even though most of these folks are still using those quads like crazy, I presume. You know, just push harder and all that.

 

[coapman]

??? What should I note? I see muscular power dropping off even though most of these folks are still using those quads like crazy, I presume. You know, just push harder and all that.

You should note how much muscular power is possible by continuing to apply down force with your most powerful muscles between 3 - 5 o'c compared to what can be applied with your weakest muscles between 9 -11 o'c.

 

[coapman]

Thanks for the graph and the power analysis breakdown. At least we can now put to bed that cyclists don't pull up on the backstroke. Everyone does, it is simply a matter of the degree to which they do it.

That having been said, I must say that coming from someone with a background in mechanical engineering that your analysis was about as lame as I could possibly imagine. There is a lot in that data and it is simply silly to conclude that because muscular power is positive (even if barely so, check out 11 o'clock) around the entire circle that there is "nothing to fix". There is simply nothing in that data to suggest that everything is "perfect" because all you have done is measure what people are currently doing. Why are the muscles doing so much less work coming across the top compared to the bottom? Are the quads that much smaller than the hamstrings? Is it really not possible for the lifting muscles to not be trained to do more in relation to the "pushing" muscles? Before one can say there is nothing to fix one needs to know more about how the different muscles are being used and what the potential of those muscles are.

Edit: somehow my edit was put in the wrong place (brain fart I suppose). I will redo. This is a thread regarding PowerCranks, cranks designed to train the athlete to improve the portions of the stroke other than the pushing portion. From a mechanical engineering perspective a further question would be why it wouldn't be a good idea, if possible, to train the "pulling" phase muscles to fully unweight (or more) to bring that muscular power to be closer to that of the "pushing" phase, if that were possible? Do you see an advantage coming to the athlete if the weaker parts of the stroke can be brought closer to the stronger part of the stroke through training? Isn't an extra watt on the backstroke (or the top or the bottom or all of those) the same as an extra watt on the downstroke? Or, do you see training as a zero sum game. If so, why?

Anyhow, welcome. Stand by to defend your views.

He did not say there is nothing to fix. He said there is nothing to fix by additional pulling up and he is 100% correct. It is not a good idea to train the pulling up muscles because the more you pull up during steady riding, the more you will lose in your down stroke.

 

[FrankDay]

He did not say there is nothing to fix. He said there is nothing to fix by additional pulling up and he is 100% correct. It is not a good idea to train the pulling up muscles because the more you pull up during steady riding, the more you will lose in your down stroke.

It isn't a matter of "fixing" anything. It is a matter of gaining power. A watt on the "pulling" side is just as valuable as a watt on the pushing side. Just as a watt over the top is just as valuable as a watt anywhere else. Look at how weak those riders were going over the top, a part of the pedal stroke that you claim you are just as strong as their pushing. There is lots to be gained, if not "fixed", in what those people were doing.

 

[coapman]

It isn't a matter of "fixing" anything. It is a matter of gaining power. A watt on the "pulling" side is just as valuable as a watt on the pushing side. Just as a watt over the top is just as valuable as a watt anywhere else. Look at how weak those riders were going over the top, a part of the pedal stroke that you claim you are just as strong as their pushing. There is lots to be gained, if not "fixed", in what those people were doing.

The problem with that extra watt on the pulling side is you will probably lose two watts on the down side. Yes over the top is a different story but PC's cannot fix that. With PC's the muscles are continually stressed by chasing the pedal/crank and attempting to apply some torque around the pedalling circle. To apply effective or close to maximal torque over the top your muscles need to be in a relaxed state from 5 to 11 so that they can be primed and already moving faster than pedal/crank speed at 11 to get that instantaneous torque to the crank at 11 as other leg ends power application at 5 o'c.

 

[CoachFergie]

The problem with that extra watt on the pulling side is you will probably lose two watts on the down side. Yes over the top is a different story but PC's cannot fix that. With PC's the muscles are continually stressed by chasing the pedal/crank and attempting to apply some torque around the pedalling circle. To apply effective or close to maximal torque over the top your muscles need to be in a relaxed state from 5 to 11 so that they can be primed and already moving faster than pedal/crank speed at 11 to get that instantaneous torque to the crank at 11 as other leg ends power application at 5 o'c.

Do you have any data to show it is a different story or is this what you imagine occurs based on your observation of video footage of Jacques?

We can see what Frank would like us to believe but fortunately good people like Dr Martin have armed us with quality data that would suggest it is just marketing smoke and mirrors.

 

[coapman]

Do you have any data to show it is a different story.

BB should be able to supply that. What PM did Dr Martin use?

 

[CoachFergie]

BB should be able to supply that. What PM did Dr Martin use?

Utterly pathetic.

The equipment to test your claims has been around for 40 years. If what you claim is true ANY power meter will show this.

It is the same one he generously offered to set you up with at a lab in England to prove your hypothesis. You declined, preferring to hide behind vapourware.