The importance of crank length to the cyclist.

[CoachFergie]

I happen to think the data, as sparse as it is, actually supports the view that shorter cranks should offer an advantage, guess the interpretation of the data is what is open to controversy.

The data is pretty clear cut that there is no significant importance to crank length. The only person claiming so just happens to market a short crank.

 

[FrankDay]

The data is pretty clear cut that there is no significant importance to crank length. The only person claiming so just happens to market a short crank.

So, I take it you think that 4'10" women and 6' 5" men would all perform equally on the same length cranks? what crank length would you recommend for this "one size fits all" world and what do you base that upon?

 

[CoachFergie]

So, I take it you think that 4'10" women and 6' 5" men would all perform equally on the same length cranks? what crank length would you recommend for this "one size fits all" world and what do you base that upon?

Your assumptions (plus opinions or beliefs) are of no concern to me.

Your original claim was that people would see a performance benefit from moving to a shorter crank. In 1500+ posts no one has provided any data to support this.

 

[FrankDay]

Your original claim was that people would see a performance benefit from moving to a shorter crank. In 1500+ posts no one has provided any data to support this.

The original post asserted that crank length could be important to cyclists for several considerations and simply wanted to open a discussion on this issue.

I would like to open a discussion regarding the importance of crank length to bicycle racing or cycling in general.…

In summary I feel that shorter cranks do several things for the cyclist.

1. Shorter cranks will improve power output for most.
2. Although this goes completely against the conventional wisdom, shorter cranks can reduce knee stress
3. Shorter cranks allow better aerodynamic positioning without sacrificing power.

You just asserted that crank length is not important for any consideration. Do you have any hard data to support that statement or to refute any of the above possibilities I raised?

 

[CoachFergie]

You're the one making the claims you can't support. Jim Martin's presentation is there for anyone to read to see what the data says.

 

[FrankDay]

…Jim Martin's presentation is there for anyone to read to see what the data says.

Indeed. From Martin's paper:

That addresses #1 on the list

1. Shorter cranks will improve power output for most.
2. Although this goes completely against the conventional wisdom, shorter cranks can reduce knee stress
3. Shorter cranks allow better aerodynamic positioning without sacrificing power.

Now would you care to address #'s 2 and 3?

 

[CoachFergie]

Having done a lit review on knee injury in cycling I know of no data supporting crank length as a cause of injury. Main factors are seat height too high or low, cadence too high or too low and to rapid a progression in mileage or intensity of riding.

Aerodynamics is mere speculation as so many factors influence aerodynamics on the bike.

 

[FrankDay]

Having done a lit review on knee injury in cycling I know of no data supporting crank length as a cause of injury. Main factors are seat height too high or low, cadence too high or too low and to rapid a progression in mileage or intensity of riding.

Thanks for your reasonable response. First, it is hard to imagine a study ever being done looking at crank length and injury as so little variation exists in crank length that it would be hard to discern much difference. But, my point was not that crank length causes or prevents injury but that crank length affects STRESS on the knee. In rehab, people who have difficulty riding long cranks can rid shorter cranks. It may be true that crank length may be associated with injury risk but that was not my point. For those with damaged knees, such as arthritis, who desire to continue to cycle, stress on the knee can be a big deal. How much the knee is bent also affects how much force one can put on the pedal. So, it seems to me that your literature search is only touching the surface here as to what crank length does to the knee.

Aerodynamics is mere speculation as so many factors influence aerodynamics on the bike.

Aerodynamics is "mere speculation"??? Would you agree that the rider is the biggest source of drag on a bicycle? Would you agree that there are certain principles one can rely upon to make a difference (e.i, being in the aerobars is generally more aerodynamic than the tourist position, or a smaller frontal area is generally better than a larger frontal area, a tight shirt is more aerodynamic than a loose shirt, etc.)? While I admit that some of the nuances are hard to predict I think we can say that for the average cyclist out there who has a pretty awful aerodynamic position they will be more aerodynamic if they can lower their front end. And, if they can do that without losing any power they should be faster. That may not be true for the athletes you coach but I believe it to be true for the vast majority of cyclists out there, to whom the original post was directed.

 

[CoachFergie]

First, it is hard to imagine a study ever being done looking at crank length and injury as so little variation exists in crank length that it would be hard to discern much difference.

Which is what we have been saying all along.

But, my point was not that crank length causes or prevents injury but that crank length affects STRESS on the knee.

Your opinion.

So, it seems to me that your literature search is only touching the surface here as to what crank length does to the knee.

I expect the researcher felt it wasn't important enough to study.

Would you agree that the rider is the biggest source of drag on a bicycle?

That is what the data tells us.

Would you agree that there are certain principles one can rely upon to make a difference (e.i, being in the aerobars is generally more aerodynamic than the tourist position, or a smaller frontal area is generally better than a larger frontal area, a tight shirt is more aerodynamic than a loose shirt, etc.)?

Again that is what the data tells us although some things I expected to be more important were not under testing and large amount of individual variation.

While I admit that some of the nuances are hard to predict I think we can say that for the average cyclist out there who has a pretty awful aerodynamic position they will be more aerodynamic if they can lower their front end. And, if they can do that without losing any power they should be faster. That may not be true for the athletes you coach but I believe it to be true for the vast majority of cyclists out there, to whom the original post was directed.

No one is challenging the concept of aerodynamics. Only the claim that crank length is the only way to alter aerodynamic's on the bike. There are far more effective means for any rider to achieve a more aero position. As mentioned I myself (not fit, not lean and certainly not elite) have dropped my bars 4cm just from a change in the tilt of my saddle.

 

[FrankDay]

No one is challenging the concept of aerodynamics. Only the claim that crank length is the only way to alter aerodynamic's on the bike.

Where on earth do you get that I am claiming that shortening crank length is the ONLY way to alter aerodynamics on the bike? I have simply said that it is a change that might allow many riders to go lower than they otherwise could without losing power. It is something that people should consider. Why do you have an issue with that?

 

[CoachFergie]

I have simply said that it is a change that might allow many riders to go lower than they otherwise could without losing power. It is something that people should consider.

My solution cost me 50cents for an allen key and took 1min to achieve. Your solution requires new cranks and changing stem length, lifting the saddle and putting it back which alters a range of parameters.

 

[FrankDay]

My solution cost me 50cents for an allen key and took 1min to achieve. Your solution requires new cranks and changing stem length, lifting the saddle and putting it back which alters a range of parameters.

You didn't already have an allen key that would allow you to adjust your saddle? Anyhow, cool for you. But what if "your solution" doesn't work for everyone or doesn't bring them to an optimal position. One of my pro triathletes won an Ironman using 145 mm cranks he bought on the internet for $22. It is true that once I figured out this potential I did start to offer a "solution" for those who want to experiment with crank length while also learning to "pedal in circles" but if one just wants to experiment with crank length it doesn't necessarily mean it is cost prohibitive, especially compared to the other things people do to improve aerodynamics ($3-10k bike frames, $1-2k wheels) that have small effect compared to an improved body position or that they even need to use my product. No one thinks it silly for people to spend several thousands on frames and wheels for tiny improvements but you seem to think it outrageous that they should consider spending tens to hundreds for something that might have the potential to give them an even bigger benefit. If something legal has the potential to help the serious athlete then that athlete should be allowed to make that choice, or at least discuss the choice. Why do you seem to have a problem with that?

 

[FrankDay]

My solution cost me 50cents for an allen key and took 1min to achieve. Your solution requires new cranks and changing stem length, lifting the saddle and putting it back which alters a range of parameters.

You didn't already have an allen key that would allow you to adjust your saddle? And, how does one lower the front without changing the stem length or handlebars? You tilted the saddle to allow you to go lower but how did you actually lower the front with that $.50 allen wrench? Shortening the cranks and raising the seat lowers the bars relative to the seat without need to purchase a new stem, although that may also be something someone might want to do because this change facilitates going even lower. Some of the stuff you say is really pretty silly. But, beyond this, what if "your solution" doesn't work for everyone or doesn't bring them to an optimal position. One of my pro triathletes won an Ironman using 145 mm cranks he bought on the internet for $22. It is true that once I figured out this potential I did start to offer a "solution" for those who want to experiment with crank length while also learning to "pedal in circles" (is it a crime to offer two potential advantages in one product?) but if one just wants to experiment with crank length it doesn't necessarily mean it is cost prohibitive, especially compared to the other things people do to improve aerodynamics ($3-10k bike frames, $1-2k wheels) that have small effect compared to an improved body position or that they even need to use my product. No one thinks it silly for people to spend several thousands on frames and wheels for tiny improvements but you seem to think it outrageous that they should consider spending tens to hundreds for something that might have the potential to give them an even bigger benefit. If something legal has the potential to help the serious athlete then that athlete should be allowed to make that choice, or at least discuss the choice and potential. Why do you seem to have a problem with that?

 

[CoachFergie]

And, how does one lower the front without changing the stem length or handlebars?

I just relocated the spacer under the stem to above.

You tilted the saddle to allow you to go lower but how did you actually lower the front with that $.50 allen wrench?

See above.

Shortening the cranks and raising the seat lowers the bars relative to the seat without need to purchase a new stem, although that may also be something someone might want to do because this change facilitates going even lower.

If you have to put the seat back because you have shortened the cranks you will need a shorter stem.

Some of the stuff you say is really pretty silly.

Look who's talking.

But, beyond this, what if "your solution" doesn't work for everyone or doesn't bring them to an optimal position.

Good thing I have more options.

One of my pro triathletes won an Ironman using 145 mm cranks he bought on the internet for $22.

More anecdotes, YAWN.

It is true that once I figured out this potential I did start to offer a "solution" for those who want to experiment with crank length while also learning to "pedal in circles" (is it a crime to offer two potential advantages in one product?) but if one just wants to experiment with crank length it doesn't necessarily mean it is cost prohibitive, especially compared to the other things people do to improve aerodynamics ($3-10k bike frames, $1-2k wheels) that have small effect compared to an improved body position or that they even need to use my product.

Congratulations you have combined two solutions to problems that don't exist.

No one thinks it silly for people to spend several thousands on frames and wheels for tiny improvements but you seem to think it outrageous that they should consider spending tens to hundreds for something that might have the potential to give them an even bigger benefit.

Do let us know when you have some actual data suggesting a benefit before starting these spam threads rather than just your opinion.

If something legal has the potential to help the serious athlete then that athlete should be allowed to make that choice, or at least discuss the choice and potential. Why do you seem to have a problem with that?

Because you haven't ever provided any data that there is even a potential.

 

[FrankDay]

If you have to put the seat back because you have shortened the cranks you will need a shorter stem.

Wrong. Moving the seat up does move it back but it also rotates the torso down which moves the shoulders forward. Depending upon the starting position this could keep the shoulders about the same to the handlebars or even move them forward, possibly needing a longer stem (unless, of course, you move the seat even further back). Unless you have actually experimented with some of these changes you should not be posting your guesses as to what actually happens.

Because you haven't ever provided any data that there is even a potential.

Ugh, I have posted the Martin data and some anecdotal data but that surely isn't proof. Anyhow, if I had proof, then we wouldn't be discussing potential would we? Do you understand this concept of a "theoretical" but unproven benefit and how people might be interested in discussing this idea? Apparently not.

 

[CoachFergie]

Wrong. Moving the seat up does move it back but it also rotates the torso down which moves the shoulders forward. Depending upon the starting position this could keep the shoulders about the same to the handlebars or even move them forward, possibly needing a longer stem (unless, of course, you move the seat even further back). Unless you have actually experimented with some of these changes you should not be posting your guesses as to what actually happens.

I experiment with position quite a bit. Lifting the saddle up 3cm does not put it back 3cm and will also depend on seat tube angle. Seeing most of my positioning work is performance based lifting the saddle up means have to lift the stem height as well.

Ugh, I have posted the Martin data and some anecdotal data but that surely isn't proof. Anyhow, if I had proof, then we wouldn't be discussing potential would we? Do you understand this concept of a "theoretical" but unproven benefit and how people might be interested in discussing this idea? Apparently not.

The theory of crank length has been tested. Do you know what a non significant result means?

 

[FrankDay]

I experiment with position quite a bit. Lifting the saddle up 3cm does not put it back 3cm and will also depend on seat tube angle. Seeing most of my positioning work is performance based lifting the saddle up means have to lift the stem height as well.

But, you haven't done this by changing crank length significantly. Raising the saddle because one has shortened the crank length does not require raising the stem also because the hip angle at TDC actually increases.

The theory of crank length has been tested. Do you know what a non significant result means?

Yes. Do you? It certainly doesn't mean that the concept has been disproved, especially in view of Martin's raw data. In the Martin case all it means is the design may not have been powerful enough to uncover any difference. Small differences are difficult to prove because they require much more data. Looking at the Martin data certainly gives one pause that if he had only had more cyclists in the study he might have uncovered a statistically significant difference between 145 and 170. It was such a nuanced reading of his study that caused me to seriously consider and explore the potential of this change. It would have been interesting to see what the actual P difference was between 145 and 170, not simply that his data didn't make some arbitrary "significance" level, which has led you to conclude that there cannot be any value to this idea. If I had been Martin I would have "concluded" from his data: "The result was surprising and needs to be studied again to see if 145 is really slightly more powerful than 170, as the data suggests." If he had simply "concluded" this then scientific neophytes would not have been led down the wrong path as to what this study actually found. But, he didn't so you and many others have drawn the wrong conclusion as to what this study "proved". Of course, the other thing that needs to be repeated about that study is how power is affected by crank length when in the aerodynamic position, something not addressed by Martin which is something especially important to the time-trialist.

 

[CoachFergie]

We are all aware of what you think you see in the data

Fortunately Jim has done further research on the area and has provided commentary suggesting that there is no advantage in terms of power or efficiency from adjusting crank length.

Some of us accept this and keep working on the things that do improve performance.

 

[FrankDay]

We are all aware of what you think you see in the data

Fortunately Jim has done further research on the area and has provided commentary suggesting that there is no advantage in terms of power or efficiency from adjusting crank length.

Ugh, have you also noticed this as to what Martin is now saying?

The Good News:
• Cyclists can ride the cranks they prefer without concern of decreasing efficiency

• Crank lengths can be chosen to meet other criteria:
• Aerodynamic position (shorter)
• Ground clearance (shorter)

The fact that these power and efficiency changes are small does not mean they are not important to the very serious. And, it has never been shown that these power and efficiency changes remain small when in the aero position. Either way, even Martin now agrees that crank length can have an impact on aerodynamics, one of the major thoughts I had that started this thread that you, seemingly, cannot wrap your mind around. I suspect it is because you are a neophyte to this science stuff, relying on others to interpret this stuff for you.

Anyhow, Martin's published data is available to all for each of us to draw our own conclusions, even if they differ from the author, should we desire. That is the way of science. That is what should lead to a healthy discussion as hard as that is for you to understand.

 

[CoachFergie]

Either way, even Martin now agrees that crank length can have an impact on aerodynamics, one of the major thoughts I had that started this thread that you,

No you started making the claim that running a shorter crank increased performance and gave a BS story of a rider improving in a hilly race as your best evidence. Failing to suggest that a year between events may have been all the difference if the fact the course and distance was different

Bit like all the other Frank Day claims that have been proven false. Jim Martin was even good enough to clear up your delusions on Slowtwitch but hey "never let the facts get in the way of a good marketing claim" eh Frank.

 

[FrankDay]

No you started making the claim that running a shorter crank increased performance and gave a BS story of a rider improving in a hilly race as your best evidence. Failing to suggest that a year between events may have been all the difference if the fact the course and distance was different

Bit like all the other Frank Day claims that have been proven false. Jim Martin was even good enough to clear up your delusions on Slowtwitch but hey "never let the facts get in the way of a good marketing claim" eh Frank.

Ah yes, when facts are insufficient it is time to resort to the ad hominem attacks. Back to the Fergie of old.

If only Dr. Martin would "be good enough" to come here and clear up a few delusions. (Or, perhaps, you could provide us with the specific link to his ST "clearing up" post.) I won't hold my breath.

 

[CoachFergie]

Ah yes, when facts are insufficient it is time to resort to the ad hominem attacks. Back to the Fergie of old.

Again, look who's talking.

 

[CoachFergie]

Juvenile I know but can't resist.

Trains using Powercranks...

Ullrich, Bettini, Sanchez and Vinokourov race and train with a SRM.

GOLD!!!

 

[coapman]

If only Dr. Martin would "be good enough" to come here and clear up a few delusions. (Or, perhaps, you could provide us with the specific link to his ST "clearing up" post.) I won't hold my breath.

Martin's research on 'one legged' pedaling did not help Powercranks.

 

[FrankDay]

Martin's research on 'one legged' pedaling did not help Powercranks.

Are you referring to the Abiss paper? Here is what Dr. Martin himself has said about that failure (his remarks are, in part, valid for almost every PC study thus far): "While it is true that we did not obtain a performance improvement we did not really expect it after only 6 total workouts over three weeks. Anytime you design a study you are constrained by what you believe the participants are will to do and how much time they will take off of their normal training. We decided on three weeks knowing it might not improve performance. That's where the analysis of muscle biopsies came in. We pulled biopsies before and after each block of training (single and double) and analyzed the tissue. The results for increases in glut-4 (insulin and contraction mediated glucose transporter) and CoxII and CoxIV (limiting steps in the respiratory chain) are highly compelling. They suggest that this will be a potent training stimulus as well as clinical modality. "

Martin demonstrated that training those additional muscles have the potential to benefit performance (even though talking about potential seems to be lost on many here). The paper's abstract concludes: "Single-leg cycling may therefore provide a valuable training stimulus for trained and clinical populations." How does that "not help" PowerCranks?

A further comment or two about one-legged training. One-legged pedaling, while training the muscles does nothing to train the two-legged unconscious coordination. It does little good to train the muscles if the brain isn't going to use them in competition. That is the biggest weakness of one-legged training IMHO. And, further, most people do one legged training for periods ranging from 5-10 minutes at cadences of 30-50. How does that prepare one to use those muscles for a 1-5 hour race at cadences of 80-100? That inadequate aerobic stimulus is the second big weakness of one-legged training. PowerCranks training solve both these weaknesses of one-legged training by making the entire training session a one-legged pedaling session for both legs at the same time.