The Powermeter Thread

[CoachFergie]

SRM and Powertap accurately measure torque but measuring force vectors through the pedal stroke requires specialist equipment. ICrank, Pioneer, SpinScan, Wattbike etc make various claims about measuring power through the pedal stroke but the validity of these claims has yet to be shown.

As per usual anyone can make a claim but backing it up with valid and reliable data is where their claims fall down.

 

[Tapeworm]

^ on the face of it these could http://axiscranks.com/

 

[CoachFergie]

I have laid my hands on a pair of those. Not practical for racing but some 2000 watt plus sprinters gave them a good work out!

Just found out the price of a software for the iCrank system is around US $2,000. With the cranks coming in at US $3,000 I would want to see a study or two confirm the validity and reliability of the data.

A discussion on the iCrank from Slowtwitch.

 

[JayKosta]

For detailed RESEARCH use, being able to measure torque & forces at specific points around the pedal rotation is very helpful.

But for individual TRAINING, it might be completely adequate to measure and display just the 'torque curve/cycle'. If the torque curve/cycle is displayed with reasonable accuracy, then the rider can change the pedel technique to get immediate feedback on how the curve/cycle reacts. This could be used by the individual to choose and develop the method that gives the best results for a particular event.

Jay Kosta
Endwell NY USA

 

[Alex Simmons/RST]

^ on the face of it these could http://axiscranks.com/

From their site:

The holy grail in cycling is to minimise what is known as the “dead spot”, which is a small window at top dead centre where the majority of crank loads are compressive. AXIS cranks can measure the size of this dead spot, and supply cues that enable the cyclist to minimise it.

If Radial loads do not turn the cranks and Tangential loads do, “it stands to reason that minimizing the Radial forces would be a good thing”

So while they have interesting technology, why does these unfounded/unproven notions persist as some kind of perceived benefit? *

Provide the measurement tool, prove it works as claimed, but please let the scientific process assess whether or not such such notions have any valid grounding for performance improvement (because so far the science would suggest it doesn't).

* Consider that a rhetorical question, lest it derail the thread....

 

[CoachFergie]

Probably better discussed in the pedalling technique thread.

But when a product makes emotive comments like "the Holy Grail" I tend to want to see an independent verification of those claims even more. Not being the kind of guy to take things on faith.

 

[coapman]

Fergie, what does this have to do with the topic of discussing the science of power meters?

For pedaling technique analysis purposes which is better, your second generation powermeter or AXIS CRANKS and explain why.

 

[CoachFergie]

For pedaling technique analysis purposes which is better, your second generation powermeter or AXIS CRANKS and explain why.

The iCrank and AXIS crank both claim to do the same thing. We await independent validation of both products.

 

[FrankDay]

For pedaling technique analysis purposes which is better, your second generation powermeter or AXIS CRANKS and explain why.

My guess is they would be pretty much equivalent. The iCranks will not give radial component forces whereas the axis cranks seem to do so. While it would seem that more information is better it is not clear that the radial information serves any purpose. Let's take a look at the forces at TDC for example. The radial forces would be directly down and I expect would be mostly be due to gravity (the weight of the leg on the pedal). That force requires zero energy expenditure on the part of the rider. Attempts to minimize that force by unweighting the leg here would require an energy expenditure but provide no power increase. Such an attempt would only reduce efficiency. Since we don't really have the ability to separate out those forces on the pedals that are due to muscular action from those forces due to non-muscular action (gravity, centrifugal forces) this explains why studies that compare the total forces on the pedal with efficiency seem to get results that defy logic. Therefore, it seems to me that the only force of any real interest to the rider from a training perspective is the tangential force as changing that actually changes power. Having more data in the form of radial data also, it seems, only has the ability to confuse things and can hurt the rider who might try to minimize forces that shouldn't be messed with.

So, it seems to me that the iCranks system is probably superior, even though it gives less data, since it focuses on the most important forces involved in power production and eliminates the forces likely to confuse the typical user.

 

[sciguy]

My guess is they would be pretty much equivalent. The iCranks will not give radial component forces whereas the axis cranks seem to do so.

Thought you mentioned that they would give radial forces last summer?


Quote:
Originally Posted by sciguy View Post
I see one shortfall of this system compared to the potential information that might be provided by a properly functioning Garmin pedal based system. The crank arm based system will be unable to "see" forces applied other than those tangential to the crank axle. It will "sense" positive or negative torque on each side but will miss forces that are not tangential to the axle. For example if a rider was applying a significant upward force when the pedal was already at TDC or downward one when the pedal is at BDC these will not be measured. It may still provide some interesting data but nearly as much as a pedal based system could potentially offer.

YMMV,

Hugh

Quote FrankDay
No, that is not true. A properly designed crank based system should be able to see all the forces that a pedal based system should be able to see. It is simply a matter of interpreting the data properly.

The developers of this system make a very high end exercise bike in which they originally had two SRM systems installed to give the left right data. This system would only be capable of doing the tangential analysis, which is what the graph shows. They developed the PowerCranks system as a much cheaper alternative that would give them even more data and, they are telling me, is even more accurate than the SRM. Now, whether this data is presented to the user or not is a different story. Not sure what they will do here. Garmin and Look have similar issues, how to best present the data they are collecting. If it is too complicated no one will be able to use it which will hurt sales. Perhaps, they will choose to have simple output with the option of more detailed analysis for those who need it. We will see. I know my people are still working on this.

The drawback of my system is few will choose to race on it. But, then, is that really a drawback? I doubt any will look down during a race, take a close look at their output device, and say, "Ooops, notice I am not very tangential, need to change that!" I see all this extra information as training useful, not race day useful. "


So what you told us in last June was not so true?

Hugh

 

[FrankDay]

Thought you mentioned that they would give radial forces last summer?


Quote:
Originally Posted by sciguy View Post
I see one shortfall of this system compared to the potential information that might be provided by a properly functioning Garmin pedal based system. The crank arm based system will be unable to "see" forces applied other than those tangential to the crank axle. It will "sense" positive or negative torque on each side but will miss forces that are not tangential to the axle. For example if a rider was applying a significant upward force when the pedal was already at TDC or downward one when the pedal is at BDC these will not be measured. It may still provide some interesting data but nearly as much as a pedal based system could potentially offer.

YMMV,

Hugh

Quote FrankDay
No, that is not true. A properly designed crank based system should be able to see all the forces that a pedal based system should be able to see. It is simply a matter of interpreting the data properly.

The developers of this system make a very high end exercise bike in which they originally had two SRM systems installed to give the left right data. This system would only be capable of doing the tangential analysis, which is what the graph shows. They developed the PowerCranks system as a much cheaper alternative that would give them even more data and, they are telling me, is even more accurate than the SRM. Now, whether this data is presented to the user or not is a different story. Not sure what they will do here. Garmin and Look have similar issues, how to best present the data they are collecting. If it is too complicated no one will be able to use it which will hurt sales. Perhaps, they will choose to have simple output with the option of more detailed analysis for those who need it. We will see. I know my people are still working on this.

The drawback of my system is few will choose to race on it. But, then, is that really a drawback? I doubt any will look down during a race, take a close look at their output device, and say, "Ooops, notice I am not very tangential, need to change that!" I see all this extra information as training useful, not race day useful. "


So what you told us in last June was not so true?

Hugh

Huh? As you can see I simply said the system should be able to present this data. I didn't know if they would present this in the final product. As near as I can tell the iCranks and Axis cranks "pick-up" are essentially the same (in fact, since both are Australian companies I have actually wondered if iCranks are actually using Axis cranks technology). What I have concluded, as I have thought about this, is the radial component information has almost zero usefulness to the racing athlete and that providing it is more likely than not to confuse the athlete and cause him to focus on areas that have no potential benefit and such focus would prevent them from focusing on areas that do have potential benefit, so a net negative. To me, this information (radial component) would only be of use to the researcher and, from what I have seen from researchers who do have access to this information that even they generally don't understand what is included in this information.

 

[coapman]

Huh? As you can see I simply said the system should be able to present this data. I didn't know if they would present this in the final product. As near as I can tell the iCranks and Axis cranks "pick-up" are essentially the same (in fact, since both are Australian companies I have actually wondered if iCranks are actually using Axis cranks technology). What I have concluded, as I have thought about this, is the radial component information has almost zero usefulness to the racing athlete and that providing it is more likely than not to confuse the athlete and cause him to focus on areas that have no potential benefit and such focus would prevent them from focusing on areas that do have potential benefit, so a net negative. To me, this information (radial component) would only be of use to the researcher and, from what I have seen from researchers who do have access to this information that even they generally don't understand what is included in this information.

How many measurements are taken by icranks on each revolution of the crank. Axis claim 200 per second.

 

[sittingbison]

final warning.

Off topic of "power meters" will result in a ban

cheers
bison

 

[FrankDay]

final warning.

Off topic of "power meters" will result in a ban

cheers
bison

I am a little confused since the most recent posts I and others made regarding the axis cranks and iCranks have disappeared as this post shows up. Since both the axis cranks and iCranks are actual power meters why does it appear that simply discussing how these new power meters will break down the power number constitute some off topic discussion on the Powermeter thread," especially since the question that led to those posts still remains? Where are we to discuss power meters that are coming that do more than just measure power (like Brim bros, Garmin vector, Rotor, Garmin, etc) and not risk being banned? Do we need to start a "Powermeters that do more than measure power" thread?

 

[CoachFergie]

I am a little confused since the most recent posts I and others made regarding the axis cranks and iCranks have disappeared as this post shows up. Since both the axis cranks and iCranks are actual power meters why does it appear that simply discussing how these new power meters will break down the power number constitute some off topic discussion on the Powermeter thread," especially since the question that led to those posts still remains? Where are we to discuss power meters that are coming that do more than just measure power (like Brim bros, Garmin vector, Rotor, Garmin, etc) and not risk being banned? Do we need to start a "Powermeters that do more than measure power" thread?

Noels question would have probably been better placed in the Pedalling technique thread because both the AXIS and iCrank claim to measure pedalling technique.

 

[hiero2]

Probably better discussed in the pedalling technique thread.

But when a product makes emotive comments like "the Holy Grail" I tend to want to see an independent verification of those claims even more. Not being the kind of guy to take things on faith.

I strongly agree. It has the sound of a sales pitch to convince the reader of something that ain't quite so.

 

[hiero2]

BTW - I've been absent from the forums for a spell. Weather conditions and work requirements. Sorry - but I'd missed this lovely conversation.

I've read most of the thread from the start - and yes - I am in agreement that it has been subject to continual trolling. I'm tempted at the moment to go back and delete about half the thread to date, as either trolling, or direct responses to the trolling that do not really contribute to the topic.

It is late tho, where I am, and I'm heading off to sleep soon, so mass deletions will wait. I also see that some warnings have been issued, and some vacation days awarded to allow time for thought. I'll be back tomorrow to spend a few more hours, and will review this again at that time.

Cheers;

H

 

[FrankDay]

I strongly agree. It has the sound of a sales pitch to convince the reader of something that ain't quite so.

Power meters that also gather data regarding pedaling technique are coming whether you think there is anything to this information or not. This goes well beyond the iCranks and Axis cranks to include Brim Bros, Rotor, Garmin Vector, Pioneer, others. Isn't that what forums are for, to allow interested people to discuss these issues?

Here is the problem that you have caused by this unnecessary meddling as I see it. How do those of us who want to discuss this issue do so without going "off topic"? It is clear that power meters and pedaling technique are merging when power meters are soon going to be also measuring technique. You might be surprised to know this but some people actually think this is going to be a big advance in power meter technology. Are you really saying that it isn't appropriate to talk about power meters that also measure technique on the power meter thread? That any such mention of these meters are off topic? After all, you allow mention of SpinScan analysis in power meter threads (an attempt to measure technique) without such intervention.

Anyhow, Noels question, while you thought it might have been better placed in the pedaling technique thread, was simply an extension of two other posts by Jay Kosta and Alex Simmons an extension of a topic that had come up before. And, in my answer, which was deleted (along with a follow-up by Sci-Guy), there was no discussion regarding technique but only a technical question to the difference between these two meters and whether those differences were important or not (exactly what Noel asked) yet somehow the answer to that question was seen as off topic, but the question remains. I guess it will remain unanswered, at least by me, even though the question was directed towards me.

So Noel asked his question to me regarding a topic that had been discussed before by himself and others on this thread about a power meter and my answer is seen as off topic.

I guess if you don't want to discuss power meters that measure technique in the power meter thread then we should change the topic to power alone prohibit any mention of meters. Why you would want to prohibit any discussion of new technology is beyond me, but that seems to be where you are headed.

 

[CoachFergie]

Noel has shifted his question to the pedalling technique thread where the discussion of the measurement of pedalling technique is far more appropriate.

Here we can discuss the measurement of power.

You have started a thread about the application of physiology to cycling (I assume).

Everything in it's place.

 

[CoachFergie]

http://video.cyclingnews.com/video/...e-at-team-sky-and-clean-cycling-6g0I6KUsY10JE

Numbers: measuring the riders while racing and training.

Power: objective measures of cycling fitness and the demands of the sport.

Power to weight: Relative power, I would expect Sky also measure aerodynamics as well.

Numbers to inform decisions: using the data to make decisions on which riders for which races, what riders need to focus on when preparing for events.

Relating the numbers to the racing. While I measure power of junior riders it is too big a gap to coach them in terms of improving power. While the power helps inform my coaching decisions the numbers I talk to juniors about is more about times they should achieve or placings they should target to gain selection.

Can see why Team Sky bring their A game to most Pro Tour races.

 

[sittingbison]

FrankDay, this post might clear this up you:

... I thought I would start a power meter thread to discuss the science behind this measurement tool....

Peddling technique in the peddling technique thread??

 

[FrankDay]

Originally Posted by CoachFergie View Post
... I thought I would start a power meter thread to discuss the science behind this measurement tool....

FrankDay, this post might clear this up you:

So, you're saying that it isn't appropriate to discuss newer power meters and how they are different from what everyone is used to? Are you saying discussing how a power meter breaks down the forces it sees to determine the power it displays has nothing to do with science? In fact, breaking down those numbers has everything to do with science.

It is just bizarre that some think it isn't appropriate to discuss all power meters in the power meter thread. I look forward to the first time someone posts their experience with Brim bros or one of the other new PM's here and see what happens. You ought to be asking yourself why are pm manufacturers choosing to provide this extra information. That would be a good topic for discussion. But, I guess if you prohibit such discussions, you can pretend these changes aren't happening.

 

[CoachFergie]

So, you're saying that it isn't appropriate to discuss newer power meters and how they are different from what everyone is used to? Are you saying discussing how a power meter breaks down the forces it sees to determine the power it displays has nothing to do with science? In fact, breaking down those numbers has everything to do with science.

It is just bizarre that some think it isn't appropriate to discuss all power meters in the power meter thread. I look forward to the first time someone posts their experience with Brim bros or one of the other new PM's here and see what happens. You ought to be asking yourself why are pm manufacturers choosing to provide this extra information. That would be a good topic for discussion. But, I guess if you prohibit such discussions, you can pretend these changes aren't happening.

Stop trolling Frank.

If a power meter combined coffee making facilities this wouldn't be the thread to discuss which type of coffee bean people prefer.

 

[CoachFergie]

Heres a few stats from Gent-Wevelgem from Jesse Sergent's SRM for anyone interested (from his Facebook page):
- 4 hours 28 mins
- 187.3km
- 41.9km/h av speed
- 306 av watts
- 81.6 RPM av
- 1209m of vertical climbing
- 4922kJ burnt
- 1262 max watts
- 1.3 degrees av temperature
51km/h av speed for the 1st hour.

 

[hiero2]

Heres a few stats from Gent-Wevelgem from Jesse Sergent's SRM for anyone interested (from his Facebook page):
- 4 hours 28 mins
- 187.3km
- 41.9km/h av speed
- 306 av watts
- 81.6 RPM av
- 1209m of vertical climbing
- 4922kJ burnt
- 1262 max watts
- 1.3 degrees av temperature
51km/h av speed for the 1st hour.

Ya know what I get out of that? It was freakin' COLD there!

Crazy weather!