The Powercrank Thread

[sciguy]

Below I will add the measured pedaling technique of a pro triathlete with about 10 years of PowerCranks training behind him. Such a technique can only be accomplished with a pretty flat muscular work rate being observed around the entire circle.

Note this athlete is actually doing positive work on the upstroke and about the same amount of work over the top as across the bottom. Compared to the work distribution of Dr. Martin's subjects this subject (pro triathlete Petr Vabrousek) has a very even work distribution.

It would have been especially interesting and perhaps telling if you'd been able to capture Petr's pedal stroke while doing some work at a significantly greater wattage. One hundred sixty watts must be a lower output than Petr does any time but coasting. I'd really love to see his pattern at 600+ watts

Hugh

 

[FrankDay]

It would have been especially interesting and perhaps telling if you'd been able to capture Petr's pedal stroke while doing some work at a significantly greater wattage. One hundred sixty watts must be a lower output than Petr does any time but coasting. I'd really love to see his pattern at 600+ watts

Hugh

While interesting I think it a little unfair to expect a pro to do such an effort at an expo 2 days before a big race. This was done with him riding 145mm cranks so the actual power is about 20% higher than shown (the cranks are calibrated to 172.5mm and this is the approximate calibration adjustment my testing has shown) or about 190 watts. He also was wearing my shoes and didn't like the cleat placement (way back) nor the way the bike fit. In addition, he also didn't like the way it felt riding with the cranks locked out. How he could tell with that pedaling pattern puzzles me but it was something he commented on. He was the one to express interest in what his stroke looked like so we did the best we could. I might add he was not looking at the screen when he was pedaling. This is simply what he was doing naturally. I was pretty amazed as it was by far the roundest effort I have ever seen anyone do, including me.

 

[JamesCun]

While interesting I think it a little unfair to expect a pro to do such an effort at an expo 2 days before a big race. This was done with him riding 145mm cranks so the actual power is about 20% higher than shown (the cranks are calibrated to 172.5mm and this is the approximate calibration adjustment my testing has shown) or about 190 watts. He also was wearing my shoes and didn't like the cleat placement (way back) nor the way the bike fit. In addition, he also didn't like the way it felt riding with the cranks locked out. How he could tell with that pedaling pattern puzzles me but it was something he commented on. He was the one to express interest in what his stroke looked like so we did the best we could. I might add he was not looking at the screen when he was pedaling. This is simply what he was doing naturally. I was pretty amazed as it was by far the roundest effort I have ever seen anyone do, including me.

Another piece of anecdotal 'evidence' with a dozen qualifiers added to simply explain the rather pointless results. Will be great to see some more rigorous analysis when you have the PM up and running fully.

Glad the good Dr could provide some very clear and well researched graphs to explain things. Looks much different than your initial claim that work was constant around the circle with gravity removed from the equation...

 

[FrankDay]

Another piece of anecdotal 'evidence' with a dozen qualifiers added to simply explain the rather pointless results. Will be great to see some more rigorous analysis when you have the PM up and running fully.

Do you want to know the full story or not? Sheese!

Glad the good Dr could provide some very clear and well researched graphs to explain things. Looks much different than your initial claim that work was constant around the circle with gravity removed from the equation...

It remains to be seen how clear and well researched those graphs are. I'll wait for the paper. Until then it is better than nothing. As I said, to me, those graphs raise more questions than they answer. Further, I think you should remember that those graphs were the result of testing non-PowerCranks trained riders (people like yourself). Further, he doesn't show the variation between riders observed. (with that average across the top some of his riders had to be producing negative muscular work there, we will see I suppose.) The constant work claim comes about from the analysis of Petr's graph, a long-term PowerCranker. Such a graph can only come about by an almost constant muscular work being done around the circle. Constant work around the circle is the ideal that I currently think PowerCrankers should strive for for optimum power and efficiency.

 

[JamesCun]

Do you want to know the full story or not? Sheese!
It remains to be seen how clear and well researched those graphs are. I'll wait for the paper. Until then it is better than nothing. As I said, to me, those graphs raise more questions than they answer. Further, I think you should remember that those graphs were the result of testing non-PowerCranks trained riders (people like yourself). Further, he doesn't show the variation between riders observed. (with that average across the top some of his riders had to be producing negative muscular work there, we will see I suppose.) The constant work claim comes about from the analysis of Petr's graph, a long-term PowerCranker. Such a graph can only come about by an almost constant muscular work being done around the circle. Constant work around the circle is the ideal that I currently think PowerCrankers should strive for for optimum power and efficiency.

I think many find it interesting that you expect so much of other peoples data and yet you don't live up to those expectations with your own data and claims.

The fact that you are willing to outlast everyone in a discussion doesn't mean you have the correct ideas or the most evidence to support your views. It probably just means you have the most to gain from 'proving' that your product works. Other people choose not to beat their head against a wall constantly.

 

[CoachFergie]

I think many find it interesting that you expect so much of other peoples data and yet you don't live up to those expectations with your own data and claims.

The fact that you are willing to outlast everyone in a discussion doesn't mean you have the correct ideas or the most evidence to support your views. It probably just means you have the most to gain from 'proving' that your product works. Other people choose not to beat their head against a wall constantly.

Graphs and charts are easy to make up. Franks charts are an epic science fail.

One can have confidence in Dr Martin's lab and results. Years of adding to the peer review research in cycling physiology and biomechanics.

The contribution of the ankle joint is higher than I would have expected so it will be good to see the results published with confidence intervals etc.

 

[JayKosta]

...
The contribution of the ankle joint is higher than I would have expected so it will be good to see the results published with confidence intervals etc.

=============
I might have missed it, but was there an explanation of how the amount of work was attributed to the various joints and their related muscles?

My thought is that for the ankle joint to be actually producing power and doing work (as opposed to mainly stabilizing the ankle), the pedaling technique would include a large and obvious amount of ankle flex and extension.

I fully expect that the muscles which control ankle motion would be very active to stabilize the ankle, but without producing much actual joint movement. I suppose this could be detected and quantified with high-speed motion photography.

In your experience, have you noticed top performing riders using large amounts of ankle motion?

Jay Kosta
Endwell NY USA

 

[CoachFergie]

In your experience, have you noticed top performing riders using large amounts of ankle motion?

Not really.

As a coach I am looking for areas to improve their results.

As a sport scientist I am looking at better ways to model performance, assess riders abilities and develop better means of tracking training loads over time.

So while I haven't seen anything of interest come from independent cranks the data Dr Martin has presented has piqued my interest as a high performance cycling coach and sport scientist.

 

[FrankDay]

=============
I might have missed it, but was there an explanation of how the amount of work was attributed to the various joints and their related muscles?

you didn't miss anything. There was no explanation.

 

[Alex Simmons/RST]

One can have confidence in Dr Martin's lab and results. Years of adding to the peer review research in cycling physiology and biomechanics.

The contribution of the ankle joint is higher than I would have expected so it will be good to see the results published with confidence intervals etc.

I was looking at that and trying to relate it to my personal experience pre and post amputation. The loss of ankle joint and lower leg on one side cost me 15-17% off my peak power (standing start or out of saddle sprint).

 

[FrankDay]

I was looking at that and trying to relate it to my personal experience pre and post amputation. The loss of ankle joint and lower leg on one side cost me 15-17% off my peak power (standing start or out of saddle sprint).

Are you saying that the one leg lost 30-34% power from loss of the lower leg?
Edit: btw, standing start is not peak power, it is peak torque.

 

[elapid]

Sure I do, check out post 882 in this very thread.Your weak knowledge base in certain areas or lack of reading comprehension is not particularly good evidence I have made errors. But, it is the internet so you are, of course, welcome to state your opinion.

Post #882 was an admission of an error? Really, have you read that post? Where is the admission of an error? Regardless, your errors are obvious to all but you.

Similarly, you are welcome to state your opinion. After all, that is all you have been able to offer because you certainly have not been able to provide any EVIDENCE that PCs work as claimed. Furthermore, because your opinions are littered with basic errors, your musings, like your claims, cannot be trusted. At least I/we have been able to provide references to counter your opinions.

 

[elapid]

Rarely would I agree with frank. But, the knee joint can move in space without the knee angle changing. Sure would be easier to talk about the upper leg/thigh/femur moving, but I think most understand that the knee moves up and down when you pedal a bike.

Disagree. For the knee angle not to change is anatomically impossible unless you want to do a Frank-like surgical fusion or splint/cast scenario. With seated pedalling, you are fixed on the saddle and pedal but leg length changes approximately by the length of your cranks x 2. Assuming a crank length of 175mm, this means that leg length will change by 35cm. The hip joint, knee joint, and ankle joint need to extend to be able to accommodate the increased leg length, which is at a maximum at 6 o'clock.

This has been shown in the following reference where the range of motion (ROM) in the knee was 66 degrees during normal pedalling (range, 46-122 degrees flexion): Ercison et al: Joint Motions of the Lower Limb during Ergometer Cycling. J Orthop Sports Phys Ther. 9(8):273-278, 1988. The ROM in the knee is greater than either the hip (mean 38 degrees) or ankle (mean 24 degrees). The hip, knee, and ankle joint motions were influenced by changes of the saddle height or pedal foot position; and different workloads had a small but statistically significant influence on the joint motions.

 

[elapid]

I think many find it interesting that you expect so much of other peoples data and yet you don't live up to those expectations with your own data and claims.

The fact that you are willing to outlast everyone in a discussion doesn't mean you have the correct ideas or the most evidence to support your views. It probably just means you have the most to gain from 'proving' that your product works. Other people choose not to beat their head against a wall constantly.

+1. Love it!

 

[elapid]

My thought is that for the ankle joint to be actually producing power and doing work (as opposed to mainly stabilizing the ankle), the pedaling technique would include a large and obvious amount of ankle flex and extension.

While researching joint ROM to answer JamesCun's post, I came across this paper which may provide some insight into your question:

Eur J Appl Physiol. 2007 Apr;99(6):659-64.
Effect of pedaling technique on muscle activity and cycling efficiency.
Cannon DT1, Kolkhorst FW, Cipriani DJ.

Abstract
The purpose of this study was to examine the acute effect of talocrural joint position on muscle activity and gross mechanical efficiency (GE). Eleven trained cyclists participated in three randomized 6-min cycling bouts at approximately 80% of maximal aerobic capacity on an electromagnetically braked cycle ergometer while oxygen consumption and muscle activity (EMG) were monitored during the subject's self-selected pedaling technique (control) and while using a dorsi- and plantarflexed pedaling technique. The mean differences in range of motion of the dorsi- and plantarflexed technique from the control position were 7.1 +/- 4.4 and 6.9 +/- 5.4 degrees , respectively. Gastrocnemius EMG activity was higher with the dorsiflexion technique than when using the self-selected control position (33.2 +/- 13.0 and 24.2 +/- 8.4 microV s, respectively; P < 0.05). Moreover, GE was 2.6% lower while riding with the dorsiflexion technique than the control position (19.0 +/- 1.2 and 19.5 +/- 1.3%, respectively; P < 0.05). The data suggested that introducing more dorsiflexion into the pedal stroke of a trained cyclist increases muscle activity of the gastrocnemius lateralis and decreased GE when compared to the self-selected pedal stroke.

 

[coapman]

=============
I might have missed it, but was there an explanation of how the amount of work was attributed to the various joints and their related muscles?

My thought is that for the ankle joint to be actually producing power and doing work (as opposed to mainly stabilizing the ankle), the pedaling technique would include a large and obvious amount of ankle flex and extension.

I fully expect that the muscles which control ankle motion would be very active to stabilize the ankle, but without producing much actual joint movement. I suppose this could be detected and quantified with high-speed motion photography.

In your experience, have you noticed top performing riders using large amounts of ankle motion?

Jay Kosta
Endwell NY USA

The ankle and lower leg muscles of the natural pedaller make the same contribution to crank torque power generation and application as that of Alex's prosthesis. The fact is they don't know how to use them, if they did, they too could be applying maximal torque through 12, 1, and 2 o'c.

 

[JamesCun]

LOL. What Frank would like you to believe is that everyone (even those who have never heard of PowerCranks) use all of the muscles of the legs to generate power around the entire pedaling circle. Now, thanks to the wonderful data of Dr. Martin, that is, finally, easily demonstrated to the "just push harder" crowd. It simply makes sense to me that if one is interested in increasing power that it would be better to try to better train all those muscles (and, perhaps, a little more) than to concentrate on a few of them involving only a small part of the circle. PowerCranks simply make that "train them all" choice "easily" possible while also, hopefully, doing a little something for technique too.

These are all just guesses and assumptions on your part. 'It simply makes sense to me' is not a valid reason. You need to be able to back up those 'gut feelings' or people will continue to doubt your product. There is a trade off for everything. Has it occurred to you that pulling harder from 3-12 might not increase the overall performance of a cyclist?

All of your claims are testable, but you choose not to test them. You expect thousands of people to take a lap of faith instead of one person testing it properly. I expect drugs to be tested and verified before they are sold, not to have a drug rep say 'it seems to make a sense' so just give it a try and see if it works.

 

[Bio_McGeek]

Yes, thanks Jim, that is really great insight into what is really happening. Some very cool science coming from your lab!

Thanks Hamish! With any luck I might get to meet you in person in NZ in December.
The data that I have reported were calculated using standard inverse dynamic techniques. The raw data were recorded from a force measuring pedal and a motion capture system.
It seems there is an interest in what each joint is doing throughout the cycle. Many authors have reported joint powers and joint moments starting back in the 80s. You can see a thorough exploration of joint powers in the Elmer et al paper here.
The key figure from that paper is pasted below. When interpreting these joint powers, keep in mind that all three joints are spanned by uniarticular (muscles that span only one joint) and biarticular muscles (muscles that span two joints). Those muscles have opposite actions at the two joints so the individual joint action doesn't tell the whole story. Most notable example is knee power which goes negative during the last part of the extension phase. At that same point, hip extension power is very high. Thus, this negative knee power likely reflects use of hamstrings to extend the hip which is corroborated by EMG data. Hamstrings will be producing positive muscular power which happens to appear as positive at the hip and negative at the knee. This is why I originally showed the figure of net muscular power; I figure its easier to digest. Hopefully these data will be helpful to you as you think about training and technique issues. These data only represent what cyclists do. I make no claim to know what they ought to do.
I am not enjoying the "banter" that occurs here at all so this will likely be my last post in this series.
Cheers,
Jim

 

[FrankDay]

While researching joint ROM to answer JamesCun's post, I came across this paper which may provide some insight into your question:

Eur J Appl Physiol. 2007 Apr;99(6):659-64.
Effect of pedaling technique on muscle activity and cycling efficiency.
Cannon DT1, Kolkhorst FW, Cipriani DJ.

Abstract
The purpose of this study was to examine the acute effect of talocrural joint position on muscle activity and gross mechanical efficiency (GE). Eleven trained cyclists participated in three randomized 6-min cycling bouts at approximately 80% of maximal aerobic capacity on an electromagnetically braked cycle ergometer while oxygen consumption and muscle activity (EMG) were monitored during the subject's self-selected pedaling technique (control) and while using a dorsi- and plantarflexed pedaling technique. The mean differences in range of motion of the dorsi- and plantarflexed technique from the control position were 7.1 +/- 4.4 and 6.9 +/- 5.4 degrees , respectively. Gastrocnemius EMG activity was higher with the dorsiflexion technique than when using the self-selected control position (33.2 +/- 13.0 and 24.2 +/- 8.4 microV s, respectively; P < 0.05). Moreover, GE was 2.6% lower while riding with the dorsiflexion technique than the control position (19.0 +/- 1.2 and 19.5 +/- 1.3%, respectively; P < 0.05). The data suggested that introducing more dorsiflexion into the pedal stroke of a trained cyclist increases muscle activity of the gastrocnemius lateralis and decreased GE when compared to the self-selected pedal stroke.

What the heck does that study have to do with this discussion other than making a muscle (that is doing no work) contract more (use more energy) will reduce efficiency.?

One could make the argument that the ankle joint muscles are responsible for 100% of the power since everything has to go through the ankle joint to get to the pedals. Everyone knows the ankle joint is important to cycling but that would be silly to argue. The question is how much actual power (work) do the muscles of the ankle joint add to the total work done by the glutes, quads, hamstrings, and hip flexors? 25% (20% of the total) seems a bit much to me, in fact a lot much.

 

[veganrob]

Jim,
Thanks for coming here with your test data and illustrations. Fascinating!

Rob

 

[FrankDay]

These are all just guesses and assumptions on your part. 'It simply makes sense to me' is not a valid reason. You need to be able to back up those 'gut feelings' or people will continue to doubt your product. There is a trade off for everything. Has it occurred to you that pulling harder from 3-12 might not increase the overall performance of a cyclist?

if I were an engineer, starting from scratch, designing a machine powered by 4 different engines, it would seem to me that I might expect that the most power might be achieved if I used all 4 engines to the best of each engines ability. Muscles are nothing more than engines here. All skeletal muscle have pretty much the same capability assuming an equal training status. Therefore, one might expect, for best performance, it would be best if the muscle work were divided up based on the mass of the different muscles. At least that seems like a reasonable starting hypothesis. Or, if someone brought that engine into the shop and asked you to see if you could increase the power and your diagnosis showed two engines being under utilized and the timing off would your efforts be best spent trying to correct those issues or trying to improve the power output of the engine that is currently working the best. Just sayin'...

All of your claims are testable, but you choose not to test them. You expect thousands of people to take a lap of faith instead of one person testing it properly. I expect drugs to be tested and verified before they are sold, not to have a drug rep say 'it seems to make a sense' so just give it a try and see if it works.

Yep. It is your choice. Thousands have taken that leap and have been glad they did.

 

[FrankDay]

These data only represent what cyclists do. I make no claim to know what they ought to do.
I am not enjoying the "banter" that occurs here at all so this will likely be my last post in this series.
Cheers,
Jim

Glad we got that bolded part cleared up. Anyhow, my prediction seems to have come true. These so-called experts don't like exposing what they don't know. Too bad. More is learned exploring what we don't know than regurgitating what we do.

 

[coapman]

The question is how much actual power (work) do the muscles of the ankle joint add to the total work done by the glutes, quads, hamstrings, and hip flexors? 25% (20% of the total) seems a bit much to me, in fact a lot much.

Based on Alex's results minimal power if any, but together with the lower leg muscles and a plantar flexed foot position the ankle could add a possible 30% power to each legs power output

 

[sciguy]

Yep. It is your choice. Thousands have taken that leap and have been glad they did.

Perhaps but the same thing could be said for power bracelets too.

 

[FrankDay]

Perhaps but the same thing could be said for power bracelets too.

Yep. Of course, that is evidence of nothing. The proof of the pudding is in the tasting.