The Powercrank Thread

[sciguy]

What is your "poor wife" measuring her imbalance on? Computrainer?

Where might I ask does the "poor wife" come from? She's showing a 53-47 ratio with Power2max and yes before you say it I understand their algorithm is imperfect but in her case it actually accentuates the difference. She is barely able to lift her right foot so it's probably reducing the left side's value even though that's the more powerful leg.

Why would anyone contemplate spinal surgery for such minimal "weakness", a difference that many would consider to be within the range of normal.

Her most recent MRI shows a 1.5cm X.5cm disc fragment pressing against one of the vertebral nerve roots. She has numbness, severe pain and loss of coordination in the right leg as a result.

Plus, what on earth does it mean that your wife's balance is this and Dave's or mine or anyone elses is that? .

Frank, you're the one who has long maintained that by using of Powercranks cyclists will become automatically become more evenly balanced. Here is the first Icranker you've tested and he shows a substantial imbalance. You yourself show a noticeable imbalance. Gosh I guess PCs don't cause auto-balancing.

Hugh

 

[Alex Simmons/RST]

So knowing how much power a rider produces is of no value, yet a chart that shows a guy still has "pedal technique" problems that 10 years of power cranking hasn't fixed is a success. Right.

 

[CoachFergie]

A bit of anecdotal evidence of another person who found that independent cranks didn't improve his performance...

http://james-p-smith.blogspot.co.nz/2009/08/powercranks-final-verdict.html

 

[FrankDay]

Where might I ask does the "poor wife" come from? She's showing a 53-47 ratio with Power2max and yes before you say it I understand their algorithm is imperfect but in her case it actually accentuates the difference. She is barely able to lift her right foot so it's probably reducing the left side's value even though that's the more powerful leg. [/QUOTEMy apologies, I somehow read your "dear" wife as your "poor" wife. I didn't mean any disrespect. And, no, I think you are wrong, such algorithms reduce any "measured" asymmetry. The algorithm assumes all the power comes on the downstroke and it assumes work done on the backstroke is zero and/or equal. So, any reduction on the backstroke makes the other side look weaker than it actually is. When the weak leg is weak on the backstroke this makes the stronger side look weaker so it reduces the value of the left side without reducing the value of the right. This brings the right and left values closer than they actually are masking the severity of the weakness. That seems to be case here. If you are weak on the pushing side the algorithm guesses correctly. It is why the only way to truly know what imbalances are is to actually measure them directly. A single power meter cannot do it.

Her most recent MRI shows a 1.5cm X.5cm disc fragment pressing against one of the vertebral nerve roots. She has numbness, severe pain and loss of coordination in the right leg as a result.

And, her power split gets it completely wrong and you knew it. Why on earth did you try to use her number to show that she was better than Dave's directly measured difference. They are apples and oranges and it meant nothing, and you knew it (or should have). If she was measured on the iCranks the degree of her disability would be immediately obvious and quantifiable. I will be down in S Cal next week to do some testing. Maybe we can put her on the iCranks and demonstrate that directly.

Frank, you're the one who has long maintained that by using of Powercranks cyclists will become automatically become more evenly balanced. Here is the first Icranker you've tested and he shows a substantial imbalance. You yourself show a noticeable imbalance. Gosh I guess PCs don't cause auto-balancing.

Well, I do believe that. However, that doesn't mean we will make everyone 50-50. Some people have issues that prevent such balance and most of us have a dominant side so I don't think it is reasonable to expect the PC's to turn everyone into a perfectly balanced individual.

In this case, we don't know how unbalanced Dave was when he started. Further, we didn't test him in the PC mode, it is possible he might have become better balanced when in PC mode. I think as more and more people use these we will find out how well and how fast PC's correct imbalances. So, until we have more data, a lot more data, this will remain an unanswered question. Don't you think this device (and devices like it) give us the ability to answer a lot of unanswered questions?

 

[FrankDay]

So knowing how much power a rider produces is of no value,

Well, PM's have been in wide-spread use for, what, 25 years now, and no one has yet demonstrated any benefit (over other means of doing the same thing) in helping cyclists improve power in training or racing.

yet a chart that shows a guy still has "pedal technique" problems that 10 years of power cranking hasn't fixed is a success. Right.

You don't see the lack of negatives on the upstroke as being a success when that is the major thing the PC's promise? I do. The fact that the rider, who has arthritis in one knee, demonstrates a small asymmetry is hardly a failure of the PowerCranks to balance the rider, IMHO.

 

[FrankDay]

A bit of anecdotal evidence of another person who found that independent cranks didn't improve his performance...

http://james-p-smith.blogspot.co.nz/2009/08/powercranks-final-verdict.html

Ah yes, the guy who agreed to test our claims and use the cranks exclusively for a prolonged period and then, after he got them, decided that they were too hard to do that so decided to do about half his rides including all of his hard rides, on regular cranks and then says they didn't do anything for him. He even set a personal best and then decided to change how he would measure improvement. Somehow, he always seems to forget to mention his failure to do what he agreed to do and use them as we suggest.

What is to be learned from his experience. If you use them part-time all bets are off as to what benefit you might receive. And, people wonder why we recommend exclusive use for the best benefit. This is the exact reason.

 

[sciguy]

Where might I ask does the "poor wife" come from? She's showing a 53-47 ratio with Power2max and yes before you say it I understand their algorithm is imperfect but in her case it actually accentuates the difference. She is barely able to lift her right foot so it's probably reducing the left side's value even though that's the more powerful leg.

My apologies, I somehow read your "dear" wife as your "poor" wife. I didn't mean any disrespect. And, no, I think you are wrong, such algorithms reduce any "measured" asymmetry. The algorithm assumes all the power comes on the downstroke and it assumes work done on the backstroke is zero and/or equal. So, any reduction on the backstroke makes the other side look weaker than it actually is. When the weak leg is weak on the backstroke this makes the stronger side look weaker so it reduces the value of the left side without reducing the value of the right. This brings the right and left values closer than they actually are masking the severity of the weakness. That seems to be case here.

You're absolutely correct on this. I agree that in her situation the algorithm masks the level of asymmetry and the values I referenced are of little comparative value.

If she was measured on the iCranks the degree of her disability would be immediately obvious and quantifiable. I will be down in S Cal next week to do some testing. Maybe we can put her on the iCranks and demonstrate that directly.

Thanks for the kind offer but the 3500 mile trip isn't too inviting. Thankfully our local PT has some wonderful machines designed to measure her leg strength in every conceivable direction. I wouldn't be surprised if it's a bit better at precisely examining strength compared to Icranks.

Well, I do believe that. However, that doesn't mean we will make everyone 50-50. Some people have issues that prevent such balance and most of us have a dominant side so I don't think it is reasonable to expect the PC's to turn everyone into a perfectly balanced individual.

In this case, we don't know how unbalanced Dave was when he started. Further, we didn't test him in the PC mode, it is possible he might have become better balanced when in PC mode. I think as more and more people use these we will find out how well and how fast PC's correct imbalances. So, until we have more data, a lot more data, this will remain an unanswered question. Don't you think this device (and devices like it) give us the ability to answer a lot of unanswered questions?

I agree that Icranks have a good bit of value in looking at what is really going on with people's pedaling. It's interesting that the makers have not chosen to show a vector analysis of the forces 'a la the Pioneer power meter. Is that something planned for the future?

 

[JayKosta]

Is there info available about HOW Pioneer derives the pedal 'force angle'?
I think that actual measurement would require 2 strain gages per crank arm.
Or is the 'force angle' estimated in some fashion?

Jay Kosta
Endwell NY USA

 

[FrankDay]

You're absolutely correct on this. I agree that in her situation the algorithm masks the level of asymmetry and the values I referenced are of little comparative value.



Thanks for the kind offer but the 3500 mile trip isn't too inviting. Thankfully our local PT has some wonderful machines designed to measure her leg strength in every conceivable direction. I wouldn't be surprised if it's a bit better at precisely examining strength compared to Icranks.

I though you were in S. Cal. There is a BioBike machine in Massacheusetts (I believe) and if you are in that area it might be interesting to compare that measurement to your PT. The one thing the iCranks measure that your PT doesn't is a functional weakness. It would be interesting to see how it compared and to see how well it measures and predicts specific weaknesses. We know that different muscles are active at different portions of the stroke (and the activity can be confirmed with concomitant EMG pickups) I have a PhD PT friend on the faculty at MGH who is exploring the possibility of doing just such a study, looking at the diagnostic ability of the cranks to uncover specific weaknesses. If you are in the area and would be interested in doing either of these I will see if I can fix it up.

I agree that Icranks have a good bit of value in looking at what is really going on with people's pedaling. It's interesting that the makers have not chosen to show a vector analysis of the forces 'a la the Pioneer power meter. Is that something planned for the future?

I don't know. All I can say is I have told them I would like to see both and to be able to choose. The pioneer vector analysis is subject to great misinterpretation because what is important is what the muscles are doing and the vectors include gravity vectors also. Someone could spend a lot of time trying to make vectors more tangential when, in fact, all they would be doing is wasting energy. The iCranks method quantifies the work being around the circle, which is valuable, but doesn't show the whole picture (the missing part being the vector analysis). Both outputs are necessary for a complete picture but each of them is way better than what Garmin is providing with the Vector. However, for now, no one knows which display is more useful nor exactly how to use this data for optimum benefit. Until we have both available we will just have to choose one and see what we can do with it.

 

[FrankDay]

Is there info available about HOW Pioneer derives the pedal 'force angle'?
I think that actual measurement would require 2 strain gages per crank arm.
Or is the 'force angle' estimated in some fashion?

Jay Kosta
Endwell NY USA

I am sure it is a calculated value from, probably, a minimum of 2 (possibly more) strain gauges. This is a fairly simple trigonometric calculation once one knows the relationships of the gauges and their calibration constant.

 

[FrankDay]

Both outputs are necessary for a complete picture but each of them is way better than what Garmin is providing with the Vector.

BTW, how many of you get the sense that Garmin is improving their Vector display in bits and pieces in order to sell more display units. First, the 500/800 gave left/right power. Then the 510/810 gives a number that somehow describes how circular (or something) the stroke is (500/800 doesn't give this). Wonder that the 520/820 will do that the older models won't that will require a new purchase to get? How long and how many interations before they get to what Pioneer and iCranks are doing now? It just seems strange to me that it took them so long to get their hardware "right" but their software is so lame compared to the promise many years ago.

Edit: sort of like the bike manufacturers model of making tiny changes that they call upgrades so they can sell more frames because some people simply can't live without the latest and "greatest." Just how much faster is this years bike over last years?

 

[sciguy]

Before we go too far down the rabbit hole, Tom A. posted a rather eloquent piece in a reply to H2Ofun over on Slowtwitch regarding concepts implied in the diagram shown below. http://forum.slowtwitch.com/cgi-bin/gforum.cgi?post=5104874#5104874

Since you didn't address my comment above about "negative power" (as calculated and shown on those polar plots above) not actually corresponding to "power lost", I figured I'd encourage everyone to do a little thought experiment:

Imagine a set of cranks attached to a frictionless bottom bracket, and with a mass attached to each pedal spindle equivalent to the mass of a typical leg. This system is in a gravitational field. When the crank is statically placed in various positions around the crank cycle, what happens? It would stay in whatever position it is placed, right?

Why? Because the force on one side causing a torque about the BB is balanced by a torque in the opposite direction caused by the force on the other mass.

Now, take that system and spin it up to a certain rotational velocity and let it go. What happens now? It continues to spin, correct? Why? Again, because the masses are balanced AND coupled through the crankarms. In other words, no energy is leaving the system, and thus no power is "lost". As one mass rises, it is balanced by the descending mass on the opposite side...and then they "trade off" as the cranks continue to rotate. Think of it as a "circular pendulum" of sorts

However, lets assume that the crankarms have a way of measuring torque built into them and we define "positive power" as torque in the direction of rotation multiplied by the angular velocity, and "negative power" as torque in the opposite direction of the rotation times the angular velocity. That's what those polar plots you show above assume, correct? But, does that "negative power" really mean that power is lost? No, it's an artifact of the rising mass balancing the descending mass and the definition of the term chosen.

So, from the above, it's fairly obvious that as long as one isn't actively pushing back on the rising leg, it's actually OK to have forces that result in what that device would call "negative power". In fact, up to the forces which represent the mass of the leg being risen, it's most likely preferred to have them since it allows your stronger and more efficient pushing muscles to do the job of propelling you forward. The rising leg is actually lifted merely by the descending mass of the falling leg. That saves your hip flexors for the run as well, if you're a triathlete.

So, once again, attempting to reduce "negative power" in a pedal stroke does NOT result in a reduction of "lost power", since none is lost from that mechanism in a balanced, coupled system anyway.

People tend to think of pedaling and individual legs in isolation...hence the popularity of things like single-leg drills, Spinscan, and the like. But, you pedal with BOTH legs AND their masses are coupled through the crank. That changes things...a lot.

Hugh

 

[JayKosta]

Before we go too far down the rabbit hole, Tom A. posted a rather eloquent piece in a reply to H2Ofun over on Slowtwitch regarding concepts implied in the diagram shown below.
...

====================
It all depends on how the term 'power lost' is understood / interpretated.

As you have described - the weight of the leg on the downstroke does contribute to the 'forward propulsion power'. And, if the leg on the upstroke is allowed to be 'pushed up' by the downstroking leg, then the net amount of 'forward propulsion power' is lessened. It is not that power has been 'lost', but that all opportunities for increasing power have not been utilized.

The crux of the matter is not only IF and HOW WELL the technique of unweighting on the upstroke can be trained and conditioned to give a competitive benefit, but also whether a similar amount of training time and effort would yield more benefit by being directed at some other aspect of cycling.

Jay Kosta
Endwell NY USA

 

[FrankDay]

Before we go too far down the rabbit hole, Tom A. posted a rather eloquent piece in a reply to H2Ofun over on Slowtwitch regarding concepts implied in the diagram shown below. http://forum.slowtwitch.com/cgi-bin/gforum.cgi?post=5104874#5104874

Hugh

Rather eleoquent? I would say "rather juvenile" approach to the problem. When I saw his original post

"Negative power" does not mean "power lost". To think so demonstrates a fundamental misunderstanding of the physics of coupled pedaling.

I said to myself this is one of the dumbest things I have ever seen. This further explanation just adds to it.

Why, if one were designing an engine, would it ever be considered advantageous (or, just, not a disadvantage) to have negative forces designed into the engine, reducing the power developed by the positive forces? This would be an especially interesting question if the engine were one in which the efficiency declined as the forces increased (muscle).

I have this great idea for an engine but to improve it I think I should add some negative forces right here!!!

This is just so much rationalizing trying to justify the status quo. Believe it if you want to. I just consider it so much mumbo jumbo being used to convince oneself they don't need to move on to something better.

ST doesn't want to have any actual discussions (debates) about this stuff anymore. Tell him to come here and post (and defend) his point of view.

 

[sciguy]

Why, if one were designing an engine, would it ever be considered advantageous (or, just, not a disadvantage) to have negative forces designed into the engine, reducing the power developed by the positive forces? This would be an especially interesting question if the engine were one in which the efficiency declined as the forces increased (muscle).

So let me get this straight, when we milled the heads to increase the compression ratio on the engines of the motorcycles I use to race and they put out 10% more horse power on the dyno. You're saying that we were actually making them less powerful????? It was obvious we increased the resistive forces within the engine as they became so much harder to kick over yet the net change was very positive.


Hugh

 

[Alex Simmons/RST]

ST doesn't want to have any actual discussions (debates) about this stuff anymore. Tell him to come here and post (and defend) his point of view.

You can't defend physics, it just is and doesn't care what you think/feel.


As for the left/right data on bike computers, heck that simple value depends on what is being measured, which isn't even standard.

e.g. Power balance values (i.e. left:right power ratio) from Garmin Vectors <> Power balance from a Quarq.

They are measuring different things yet use the same terminology and report via the same channel. One could get a more right dominant value from one meter and a left dominant result from the other meter, even if both meters were perfectly accurate.

 

[FrankDay]

So let me get this straight, when we milled the heads to increase the compression ratio on the engines of the motorcycles I use to race and they put out 10% more horse power on the dyno. You're saying that we were actually making them less powerful????? It was obvious we increased the resistive forces within the engine as they became so much harder to kick over yet the net change was very positive.


Hugh

I guess if you are using an engine design that uses negative forces to develop positive forces and increasing negatives allowed you to see a net positive my example would not be valid. But, we happen to be on a bicycle forum and I am not aware of any data that suggest that increasing negative forces improve the positive forces for a net gain. And, that wasn't TomA's position which was those negative forces simply don't matter at all, it is all a wash. If that were the case why unweight at all. It turns out bicycle pedals will work just fine without any negative forces so explain to me how adding negative forces on the backstroke results in an overall positive on a bicycle. I look forward to hearing your (and TomA's) argument that increasing the negative forces on the backstroke should allow us to increase power overall. Those negative simply reduce the amount of power going to the wheel. I could see his argument that those negative forces don't make any difference if it were not possible to eliminate them but it is, as Dave's data shows. Accepting them is the same as adding them. That is the problem. He is stuck in the old paradigm and is trying to make an argument to justify his still being there.

Take a close look at Dave's data again.

Let's assume Dave's pedaling technique when he starts training is like the right leg in both legs. This is unlikely as he doesn't have any negatives but let's make this assumption. He would be at 208 watts. Then he trains and learns to pedal as his left leg does but in both legs. He would then be at 270 watts, a 62 watt increase without pushing any harder. That is a 30% increase in power by simply making very tiny improvements around the 80-90% of the stroke that is pushing less than the maximum (around 110º, 200 on the graph because it is rotated 90º). And, people say 40% improvements are impossible when we are starting in people with significant negatives. If you still believe that you are ignoring the data. Knowledge is power. The knowledge is coming. Ignore it at your competitive peril.

 

[Alex Simmons/RST]

So why after 10 years of PC use has this magical 40% not happened?

I think the real question is one of opportunity cost - i.e. how much performance improvement has been lost by wasting effort on this stuff?

 

[FrankDay]

So why after 10 years of PC use has this magical 40% not happened?

It has happened lots of times. You folks just don't want to acknowledge it. Anyone who has come forth with such results simply gets shouted down and called a liar and a shill such that they have, essentially stopped trying. If you believe something impossible when someone says it happened the only explanation, in your mind, is they must be lying. But Dave's data clearly shows a 30% improvement can be seen by some very small changes in technique without pushing any harder.

I think the real question is one of opportunity cost - i.e. how much performance improvement has been lost by wasting effort on this stuff?

Based on the 1-2/1000 who send them back for their moneyback I would say not much. Or, you could ask, how much opportunity cost is lost by ignoring the potential opportunity?

 

[sciguy]

Frank,

Which of the two cards below you're trying use in your argument regarding the 40% improvement?

or

or perhaps you're insisting that :

Hugh

 

[JayKosta]

...
But Dave's data clearly shows a 30% improvement can be seen by some very small changes in technique without pushing any harder.
...

===========================
It seems that the additional power shown in Dave's left leg is due to positive power being generated by 'pulling' on the upstroke (not just unweighting).
And while the physical effort of doing that pulling doesn't require 'harder pushing' on the downstroke it does require more overall physical effort, and the resultant calorie expenditure, fatigue, etc.

Perhaps the power output 'style' shown in the right leg is better, and the pedaling goal for both legs should be more downstroke power, and simple unweighting on the upstroke.

If for some reason the downstroke power cannot be increased, then increasing power on the upstroke would be useful.

It WILL be very interesting to see scans of many successful well-training riders to learn what they really are doing ...

Jay Kosta
Endwell NY USA

 

[sciguy]

It WILL be very interesting to see scans of many successful well-training riders to learn what they really are doing ...

Jay Kosta
Endwell NY USA

Jay,

You bring up good points and I agree with wanting to see what very successful people do when they actually compete. You have to realize that when Dave or anyone else is under the microscope having their pedal stroke evaluated over a short period of time with Frank standing right beside of him there might just bit a tiny bit of influence on how they pedal.....sort of like being on your best behavior in front of you mom when you were a kid. Much more interesting data will come from unsupervised rides that last a good long time.

Hugh

 

[h2ofun]

Frank had no influence over me. )

I wish we would have unlocked the cranks to see what would happen.

I really am interested to see numbers from folks who have never used PC's as well as other folks who have used PC's. Data is good.

Once they get a head unit for the icranks, will be interesting to see data from folks racing with them, either locked or unlocked.

I just see nothing negative about gathering more data and see if any of this supports or disproves anyones thoughts.

I just never understand why things have to become personal attacks. All I have done is say here is what I have done, good or bad, and here was some data from a very quick test that I was the first one on. Seems energy could be better spent trying to see how more data can be collected, and collected better, than keep dragging up the old fights.

I continue to try and see if I an improve on things, based on how I am able to train physically, mentally, and time wise. Granted just kicking my **** is one way, but mentally, it just has not worked for me. So if I can use some gadgets to help keep me focused and excited, great. Will it make me the best I can be? Who cares my family is first and I do this to try and head of cancer.

For the folks who say lets just focus on lets try and collect data and let the cards fall where they may, thanks. For the folks who in my book just love to be a ....., well, .....

 

[CoachFergie]

Frank had no influence over me. )

Got any data to prove that?

I wish we would have unlocked the cranks to see what would happen.

Why didn't you?

I really am interested to see numbers from folks who have never used PC's as well as other folks who have used PC's. Data is good.

Yes, whole lot of studies collecting data on riders using PC's v not using PC's showing they don't improve performance.

Once they get a head unit for the icranks, will be interesting to see data from folks racing with them, either locked or unlocked.

Good to see you have read all the studies on the subject that have already been published

I just see nothing negative about gathering more data and see if any of this supports or disproves anyones thoughts.

Oh goodie, more anecdotal evidence

I just never understand why things have to become personal attacks. All I have done is say here is what I have done, good or bad, and here was some data from a very quick test that I was the first one on. Seems energy could be better spent trying to see how more data can be collected, and collected better, than keep dragging up the old fights.

Because your claims have been tested, studies have performed and data has been collected but you are ignorant of this.

I continue to try and see if I an improve on things, based on how I am able to train physically, mentally, and time wise. Granted just kicking my **** is one way, but mentally, it just has not worked for me. So if I can use some gadgets to help keep me focused and excited, great. Will it make me the best I can be? Who cares my family is first and I do this to try and head of cancer.

How is this different to any athlete? They all have goals, train and many measure their progress!

For the folks who say lets just focus on lets try and collect data and let the cards fall where they may, thanks. For the folks who in my book just love to be a ....., well, .....

Better troll on over to the Power Meter thread to see one persons take on measuring data.

 

[CoachFergie]

Just to show what a total loser Dave is here is a comment on racing and training with a power meter...

If power meters were so great, yep would seem 100% would be using, and their race results should be so much better than folks from the past who never had them.

Darn things are not cheap. So for I assume a lot of pros unless they get them for free, ....

But you want us to collect data, that has already been measured in countless studies, with iCranks.