The Powercrank Thread

[FrankDay]

With other studies of pedaling technique there was no "agenda" as in "a more ideal way to pedal" that you espouse. That makes it a whole different ball of wax and if you can't see that you're too close.

LOL. I would submit that every study has an "agenda" because every study starts with a hypothesis. That having been said, what is so silly about your concern is I am not doing a study. I am simply gathering data regarding this BRAND NEW TOOL such that I might learn stuff that will eventually help me give better advice to those who use my product and to those who might use the iCranks. Fortunately for me I am not paralyzed by the fact that the data I will be collecting will not be part of a formal study and am able to draw conclusions and make decisions based upon my own limited experience and knowledge. It will be up to others to show, by doing a study, whether the conclusions I draw are correct or not. I am posting some of the early stuff I find that I think has some relevance to the threads I post in. Thank you for pointing out for the masses some of the potential issues that you see in the data.

I do look forward to seeing data for substantial periods of time as in hours taken with the cranks locked.

Hugh

I am not sure why since this data won't be part of a study and they will all know their stroke is being recorded. What could possibly be learned from it?

 

[FrankDay]

Got a call from a customer yesterday who was having a slipping issue with the PowerCranks. Turns out his son, who is 12 is the user, AND HE HAS BEEN USING THEM SINCE HE WAS 6!!! He is, apparently, a nationally ranked BMXer. Now this is someone I need to test with the iCranks to see what his stroke looks like because he has never had to relearn anything.

 

[sciguy]

Got a call from a customer yesterday who was having a slipping issue with the PowerCranks. Turns out his son, who is 12 is the user, AND HE HAS BEEN USING THEM SINCE HE WAS 6!!! He is, apparently, a nationally ranked BMXer. Now this is someone I need to test with the iCranks to see what his stroke looks like because he has never had to relearn anything.

and while you're at it, it would also be equally interesting and perhaps illuminating to see what the pedal strokes of the athletes ranked higher than him look like

Hugh

 

[FrankDay]

and while you're at it, it would also be equally interesting and perhaps illuminating to see what the pedal strokes of the athletes ranked higher than him look like

Hugh

Of course, if that were possible. I am interested in looking at as many athletes as I can with as broad a background as I can to see what can be learned understanding, of course, that other things can set athletes apart also, stuff like training regimen, natural ability, luck, etc. It is why standardized studies that try to look at just one element are important but these, as I think you know, are extremely hard to do.

I, hopefully, will get a wide variety of abilities and experience when I put people on the cranks at expo's to be able to draw some reasonable conclusions. We will see.

 

[FrankDay]

I have done some manipulation (rotated it 90º so it reflects reality) of one of the pedal stroke analysis done on Chris Hopkinson and then compared it to what I would consider a "perfect circle" for him at this power. To me a perfect circle does not mean pulling up on the pedal as hard as you push but, rather, the pedal force diagram draws out a circle suggesting the work done around the circle by the muscles is equally divided around the circle. It doesn't matter how much he pulls up or pushes down as long as the work is equally distributed to satisfy my definition. Note that he is very close to that and that all he need do is pull up a little less, push down a little less and increase his forces across the top a little more to achieve "a perfect circle" pedaling stroke.

 

[FrankDay]

I have modified my thoughts on the above. If one assumes "perfect circles" is the most efficient method of pedaling (I know, this has yet to be proven) then it would be good to give the rider a visual feedback as to how well they are doing in this regards. Therefore, I have suggested to the iCranks people that they add to their display the capability of displaying what a "perfect circle" would look like based upon what they are doing right now. This would simply involve calculating a circle based upon the forces at 90º and 270º and superimposing it on what the rider is actually doing. This way the rider can see where the areas of improvement should be if one had a goal of improving this aspect of their stroke. One can see from my representation of what this would look like that in the case of Chris Hopkinson that if he were able to do this he would gain a fair amount of power and, since his issue is entirely coming over the top, I think this suggests that his cranks are probably too long. Anyhow, I think this would be a useful addition to the software, making it much more useful to the end user (at least for those who think this important and those that don't probably wouldn't buy the product anyhow). Comments?

 

[JayKosta]

...
If one assumes "perfect circles" is the most efficient method of pedaling (I know, this has yet to be proven) then it would be good to give the rider a visual feedback as to how well they are doing in this regards.
...

====================================
Without actual tests which indicate that 'perfect circles' are most efficient (or used successfully) by well trained highly ranked competitors, it is a mistake to start from the premise that 'perfect circles' are best or desirable. And it could be counter productive to have users attempt to achieve them.

My thinking is that due to physiology, it would surprising if actual circles are best. We are not built or function as perfect machines.
The best shape might just as well be egg-shaped (or perhaps oblong).

Definitely more testing is needed before suggesting a particular shape as a goal.

Jay Kosta
Endwell NY USA

 

[FrankDay]

====================================
Without actual tests which indicate that 'perfect circles' are most efficient (or used successfully) by well trained highly ranked competitors, it is a mistake to start from the premise that 'perfect circles' are best or desirable. And it could be counter productive to have users attempt to achieve them.

My thinking is that due to physiology, it would surprising if actual circles are best. We are not built or function as perfect machines.
The best shape might just as well be egg-shaped (or perhaps oblong).

Definitely more testing is needed before suggesting a particular shape as a goal.

Jay Kosta
Endwell NY USA

There is no basis for starting from any premise then if one is going to require actual tests "proving" one way is better than another before one can theorize same. Where is the proof that "mashing" is superior? Or, any other method?

To my way of thinking, the concept of circles as being superior would not hold any water only if it could be shown that doing so were impossible. Obviously it is possible to get quite close to a circle as demonstrated above so it makes perfect sense to me that it is best to divide the work up around the circle as much as possible and distribute it amongst as many muscles as possible. (in the above example, the rider is weak across the top which could be improved only by earlier use of the Quad muscles. Surely no one would claim they are too small to do much work.)

It seems sort of silly to bash circles as being superior because even the biggest masher is pedaling "ovals", which is nothing more than a flattened circle because then one has to wonder (and make the argument without any supportive testing) as to how much flattening is ideal? I see zero support for any argument that concentrating the work in a small segment of the stroke would lead to being more efficient or more powerful or a "more rounded" technique. I look forward to hearing that argument.

Of course, many here will choose to ignore this kind of data and insist that it is not necessary to worry about technique and that all one should do is ride their bike more. While we can all agree that riding a bike more will make people better we don't all agree that is the best way to get better. Some of us are of the opinion that technique matters and that "circles" are better than "non-circles" (whatever that may be). At least there is some evidence to suggest that more circular is better than less. Unfortunately, it is not conclusive yet.

It is my own opinion that time would be better spent asking the question as to why coming over the top tends to be the weakest part of everyone's stroke? And, then asking, can anything be done about it? I think the answer to the first question is most peoples cranks are too long making it difficult to do anything at the top of the stroke (that, and few have put any real effort into improving this part of the stroke). I think the answer to the second question is, YES! Will we ever reach "perfection"? Probably not, but we can sure get a lot closer than we do now.

 

[sciguy]

Frank,

Your "perfect circle" pedaling concept reminds me of the Catholic Church's support of the geocentric model of the universe with all the heavenly bodies traveling in perfect circles around the earth. I'd bet it is about as correct as well. It does however make for a wonderful sales pitch for an independent crank based power meter that allows one to visualize their pedal stroke. Gosh what a surprise there

Hugh

 

[FrankDay]

Frank,

Your "perfect circle" pedaling concept reminds me of the Catholic Church's support of the geocentric model of the universe with all the heavenly bodies traveling in perfect circles around the earth. I'd bet it is about as correct as well. It does however make for a wonderful sales pitch for an independent crank based power meter that allows one to visualize their pedal stroke. Gosh what a surprise there

Hugh

Don't you find your response a little disingenuous? I am willing to put my reputation on the line and say "I believe it will be shown that it is better to distribute the work around the entire pedaling circle as best as possible" and you say: That reminds me of the geocentric model of the universe without saying what model you think to be correct. It would appear you take no opinion on this issue other than I am wrong. Not only do I find that disingenuous but scientifically lazy and cowardly.

And, you are surprised that I, who think that pedaling technique really matters, might use a product that measures pedaling technique to sell a product designed to change pedaling technique? REALLY!!! You would think that if I didn't believe this were important I would be shying away from a product that could prove me wrong, yet I don't. What could possibly be wrong with me. It seems more like some of you who don't think pedaling technique important are the ones shying away from something that can prove them wrong.

So, put forth your opinion as to whether pedaling technique matters and if it does what technique you believe best. Live up to your screen name.

 

[ustabe]

Comments?

Even without knowing how optimum pedaling a perfect circle is, I like the concept of your graphic representation. But maybe perfect tangential force isn't optimum, or perhaps there's just a point where the profile is just "good enough." Perhaps the leg and foot really aren't adept at kicking with steady force over the top of the cycle. Recalling my swimming training, there were phases in the stroke where it was really a waste of energy to apply a lot of force.

I'm thinking that your inference on the length of Chris Hopkinson's cranks might be wishful thinking, or at least drawing too much conclusion from too little data. I'd like to see Hopkinson's profile while using shorter cranks. I'd also like to see profiles of more riders, PowerCrank users and non-users alike.

 

[FrankDay]

Even without knowing how optimum pedaling a perfect circle is, I like the concept of your graphic representation. But maybe perfect tangential force isn't optimum, or perhaps there's just a point where the profile is just "good enough." Perhaps the leg and foot really aren't adept at kicking with steady force over the top of the cycle. Recalling my swimming training, there were phases in the stroke where it was really a waste of energy to apply a lot of force.

all of your considerations are absolutely correct. The issue, of course, is no one knows for sure. My supposition is based upon mechanical principles and the known physiology of muscles. If I am wrong then it would be useful to understand what else plays an important role if coaching and science are to advance in this area. What boggles my mind is that so many seemingly smart people here aren't even interested in exploring the question - presumably because I am the one asking it. This is a complicated issue with many variables. It seems that if we want to advance we should be asking the question now that tools are appearing that allow us to get a few answers.

I'm thinking that your inference on the length of Chris Hopkinson's cranks might be wishful thinking, or at least drawing too much conclusion from too little data. I'd like to see Hopkinson's profile while using shorter cranks. I'd also like to see profiles of more riders, PowerCrank users and non-users alike.

I agree that we need more data. I will be testing a rider today who has no experience with PowerCranks. I am also looking for a rider who will train exclusively on the cranks and come in every couple of weeks for testing so we can follow the changes. The more data there is the easier it will be to draw valid conclusions about some of this stuff.

 

[FrankDay]

Here is some of the data I got today. I post this to show that my definition of pedaling in circles does not require actually pulling up with the pedals. The fact there is negative forces during a portion of the backstroke does not mean he is not doing work as he is still putting potential energy into the leg with the muscles partially unweighting but the force graph constitutes almost a perfect circle. This is someone not trained on PowerCranks and most of the time his stroke didn't look this round but this did show up so I am posting it to illustrate this point. The question then becomes when he increases power is he better off keeping this pattern and increasing around the circle equally or emphasizing one portion (the downstroke)? I vote for the first.

 

[JayKosta]

Here is some of the data I got today. I post this to show that my definition of pedaling in circles does not require actually pulling up with the pedals.
...

==============================================
I'm confused about how you interpret the 'pedaling in circles' graph.

Yes, the green line does appear as a nice circle, but the center of the circle is a little low and to the right of the main axis lines.
My 'word description' of the graph is that most power is produced by the downstroke, with some power being produced thru BDC, then good unweighting on the upstroke, and power starting again at TDC.

In addition to the shape of graph, its orientation is important to understand 'where' and 'how much' power is produced in a crank rotation.

Jay Kosta
Endwell NY USA

 

[coapman]

The question then becomes when he increases power is he better off keeping this pattern and increasing around the circle equally or emphasizing one portion (the downstroke)? I vote for the first.

He has no choice, it has to be the second.

 

[FrankDay]

==============================================
I'm confused about how you interpret the 'pedaling in circles' graph.

Yes, the green line does appear as a nice circle, but the center of the circle is a little low and to the right of the main axis lines.
My 'word description' of the graph is that most power is produced by the downstroke, with some power being produced thru BDC, then good unweighting on the upstroke, and power starting again at TDC.

In addition to the shape of graph, its orientation is important to understand 'where' and 'how much' power is produced in a crank rotation.

Jay Kosta
Endwell NY USA

I am quite certain the circle is centered on the Y axis and only moved to the right on the X axis. What people don't understand is this movement is coming from the effects of gravity. If this rider were pedaling like this in space his pedaling circle would be centered at 0,0 and it would be obvious to everyone he is doing equal work around the entire circle. What gravity does is move the circle to the right making it look like there is little or no work being done on the upstroke and a lot of work being done on the downstroke, which is true but only indirectly because about half the work on the downstroke is coming from the return of the potential energy put into the leg by the muscles on the backstroke, so the appearance of the work being done on the upstroke is delayed until the downstroke. A pedal force diagram that looks like a circle centered on the Y axis means the work is evenly distributed around the circle regardless of where the circle is centered on the X axis. The further away from from looking like a circle the less even the work being done around the circle. One can argue as to which pattern is better (circular, oval, or something else) but it is wrong to assume no work is being done on the upstroke because the forces seen by the pedal are small there.

 

[Alex Simmons/RST]

I am quite certain the circle is centered on the Y axis and only moved to the right on the X axis. What people don't understand is this movement is coming from the effects of gravity. If this rider were pedaling like this in space his pedaling circle would be centered at 0,0 and it would be obvious to everyone he is doing equal work around the entire circle. What gravity does is move the circle to the right making it look like there is little or no work being done on the upstroke and a lot of work being done on the downstroke, which is true but only indirectly because about half the work on the downstroke is coming from the return of the potential energy put into the leg by the muscles on the backstroke, so the appearance of the work being done on the upstroke is delayed until the downstroke. A pedal force diagram that looks like a circle centered on the Y axis means the work is evenly distributed around the circle regardless of where the circle is centered on the X axis. The further away from from looking like a circle the less even the work being done around the circle. One can argue as to which pattern is better (circular, oval, or something else) but it is wrong to assume no work is being done on the upstroke because the forces seen by the pedal are small there.

All you are suggesting is that the pedal torque generate a perfect sine wave that never goes negative and this is the means by which one generates the most power (area under the curve). This is a baseless assumption.

 

[FrankDay]

All you are suggesting is that the pedal torque generate a perfect sine wave that never goes negative and this is the means by which one generates the most power (area under the curve). This is a baseless assumption.

You have the same problem as SCIGUY, willing to come here and say something is wrong without saying what you believe is correct. All I can say is the reason for my believe is not "baseless". It might be wrong, but until I have heard a better explanation I am unpersuaded that I am wrong. In fact, received some independent data today further supports my contention. Another rider with a right/left difference of 10 watts. While neither leg is as circular as I would think optimal I think it is clear that the weaker leg is less circular than the stronger leg. (the black and red circles represent two different ways of looking at circular pedaling one based on the max/min at 90/270 and the other based on where the max is (135) and 180 from that. Again, the main issue in both cases here is coming across the top. Fix both these patterns and the rider would gain 30-40 watts without "pushing" any harder at the max point. Unless you have data to the contrary all that I have seen so far suggests that increased circularity results in increased power.

 

[Alex Simmons/RST]

I'm not making any assertion about what's correct. You are.

The reason I'm not is because:

i. we don't actually know

ii. it will inevitably be like many things in cycling (and athletic activity), i.e. individual to the person, the specific event demands etc

iii. we've already seen the torque data from a wide range of successful elite cyclists and these demonstrate quite a range of torque profiles that don't fit your world view (let alone simply observing significantly different pedalling actions from the best there ever is/was)

iv. I don't make a flawed assumption that energy transfer can magically be relocated from one muscle group to another, let alone done so with equal or better effectiveness and/or efficiency.

v. one can make changes to pedal dynamics by simple equipment positional changes, e.g. moving cleats fore/aft (with appropriate saddle positional adjustments), or in my more extreme case, amputating a leg and using a prosthetic, yet doing so has no definitive impact to maximal (aerobic endurance) performance. IOW the body is pretty adaptable.

So the onus is thus on you to demonstrate why your assertions (e.g. better circular torque symmetry = better performance) hold up to scrutiny when there is very little to support that assertion.

But your track record on such scrutiny isn't exactly strong so I'm not holding my breath.

 

[FrankDay]

I'm not making any assertion about what's correct. You are.

So, you are willing to come here and assert that I am wrong without any basis for saying so? Is that correct? You don't have a clue what is correct but you're willing to bet I am wrong?

The reason I'm not is because:

i. we don't actually know

No, but we know quite a bit that can allow us to surmise and predict. That is what I am doing. Since you don't know you don't think it possible for anyone to know or predict. What BS.

ii. it will inevitably be like many things in cycling (and athletic activity), i.e. individual to the person, the specific event demands etc

Wow, really? If everything is individual to the person how on earth does any coach or athlete know what to do? Don't you think we would be able to find some general principles that apply, in general, to most that the individual can adapt for themselves if they see evidence to suggest that something different works for them. What you are saying is you believe it is really silly that any researcher do any study looking for general principles because we are all individuals.

iii. we've already seen the torque data from a wide range of successful elite cyclists and these demonstrate quite a range of torque profiles that don't fit your world view (let alone simply observing significantly different pedalling actions from the best there ever is/was)

Yes, and it means essentially nothing because there are so many variables. The one thing that is interesting about the data I have been publishing, looking at the differences between right and left legs is that we can pretty much presume that the two legs have seen pretty much the same training such that, unless there is another explanation, that the differences between the legs are most likely explained by technique. That cannot be said about any of the studies you are referring to.

iv. I don't make a flawed assumption that energy transfer can magically be relocated from one muscle group to another, let alone done so with equal or better effectiveness and/or efficiency.

I don't make any assumption. Muscles do work when they contract with force and shorten. Muscles waste energy when they contract with force and do not shorten.

v. one can make changes to pedal dynamics by simple equipment positional changes, e.g. moving cleats fore/aft (with appropriate saddle positional adjustments), or in my more extreme case, amputating a leg and using a prosthetic, yet doing so has no definitive impact to maximal (aerobic endurance) performance. IOW the body is pretty adaptable.

??? what does that have to this argument. Regardless, I would be very interested in seeing how the pedaling dynamic of a trained BK amputee compares (circle wise) to the technique before the amputation. My guess is the amputee has a pretty good technique as I define it.

So the onus is thus on you to demonstrate why your assertions (e.g. better circular torque symmetry = better performance) hold up to scrutiny when there is very little to support that assertion.

That is what I expect to happen now that we have the ability to measure this stuff.

But your track record on such scrutiny isn't exactly strong so I'm not holding my breath.

LOL. Good, don't hold your breath. I suspect "proof" is going to take some time even though studies that support my contention already exist. http://www.ncbi.nlm.nih.gov/pubmed/10460126 But, I suppose, you have forgotten about Smak (darn, those studies that compare right and left legs and the strong and weak leg.) But, if I am wrong I am sure data that is contrary to my position will be all over the net soon. When you see some be sure to come here and post it so we can discuss it. I don't think I will hold my breath because, I suspect, it will be awhile before I see any.

 

[Alex Simmons/RST]

So, you are willing to come here and assert that I am wrong without any basis for saying so? Is that correct?

No, I am saying you have no basis for saying you are correct.

 

[JayKosta]

From the strict viewpoint of mathematics and geometry, it is true that the 'perfect circle' shape yields the greatest 'net power per rotation' for a given 'max power' value somewhere in the rotation.

Whether it is better to train with the specific goal of achieving a 'perfect circle' versus other goals such as increased downstroke power, efficiency, endurance, etc. is debatable.

Meaningful discussion can take place when more cyclists have been tested using devices such as iCranks, and results of training are compared.
I'm willing to wait.....

Jay Kosta
Endwell NY USA

 

[FrankDay]

No, I am saying you have no basis for saying you are correct.

Sure I do. You just don't understand it. Your problem, not mine.

Edit: If you are interested in, perhaps, learning something, go back and look at some of those graphs again where both left and right are together and there is a power difference and see if you can draw any conclusions as to what might account for the power difference seen. That should, one would hope, get you thinking about this stuff and, perhaps, get you on the right path. Enjoy.

 

[coapman]

The question then becomes when he increases power is he better off keeping this pattern and increasing around the circle equally or emphasizing one portion (the downstroke)? I vote for the first.



Try increasing power around the rest of the circle while leaving the downstroke power unchanged and see if you can get equal distribution of effective torque or even pedal force around the entire circle. Do you think this is possible, I don't because the rest of the circle has already reached its limit.

 

[TeoSheva]

Hi Frank,

I have a question for you from a friend of mine: the 145mm are the best choice for going uphill or it is ok even using something shorter (like 110mm)? He's 1.75m and the inseam is 87cm

thank you in advance!