The importance of crank length to the cyclist.

[onetrack]

Glad to see we can agree. It is meaningless.

From a professional coach no less. Were I being coached by you, I'd be asking for a refund just about now.

 

[CoachFergie]

From a professional coach no less. Were I being coached by you, I'd be asking for a refund just about now.

What does my coaching have to do with the meaninglessness of a gain ratio?

I assume riders choose me because I have a history of performance improvement.

 

[FrankDay]

The place I found the 41% measurement was the Jim Martin 2001 study, which also used a 20% of leg length measurement. Both came out the same for me, 172.5mm. Don't know the basis of their calculation though. I only did the exercise for interests sake to see how it compared to what I was already using.

FWIW when I did the fit calculation from the Competitive Cyclists website a few years back it also came out with around the same length crank, they probably use the same formula.

I am really confused here as to what you took from any Martin study that suggests he is giving a finding of an optimum crank length/leg length ratio. Most of the stuff I have found he suggests crank length has very little effect on power, efficiency or, almost, anything else. So, even though power was highest with shorter cranks, Martin concluded the effect was so small people could use pretty much whatever crank length they wanted without losing much. But he does have this slide in his presentation:

Hmmmm. Shorter cranks are better for aerodynamics and ground clearance according to Jim Martin. But, I guess, if all you care about is power then, by all means, use whatever crank length you want because he found the effect small. But, if you think aerodynamics and ground clearance are important to racing then I don't see how a 41% of leg length equation (or any other equation) takes this into account.

 

[CoachFergie]

Hmmmm. Shorter cranks are better for aerodynamics and ground clearance according to Jim Martin.

Only if the rider can improve their aerodynamic position. And there are more ways to improve aerodynamic position than changing crank length.

 

[Boeing]

I like the idea of testing different crank arm lengths simultaneously on the same bike. Maybe like a 177.5 drove side and a 167.5 non. I mean I am sure the added leverage on the drive side will increase watts like 2%

 

[veganrob]

I am really confused here as to what you took from any Martin study that suggests he is giving a finding of an optimum crank length/leg length ratio. Most of the stuff I have found he suggests crank length has very little effect on power, efficiency or, almost, anything else. So, even though power was highest with shorter cranks, Martin concluded the effect was so small people could use pretty much whatever crank length they wanted without losing much. But he does have this slide in his presentation:

Hmmmm. Shorter cranks are better for aerodynamics and ground clearance according to Jim Martin. But, I guess, if all you care about is power then, by all means, use whatever crank length you want because he found the effect small. But, if you think aerodynamics and ground clearance are important to racing then I don't see how a 41% of leg length equation (or any other equation) takes this into account.

It says CAN be used for aerodynamics, not ARE better for aerodynamics. Big difference.

 

[FrankDay]

It says CAN be used for aerodynamics, not ARE better for aerodynamics. Big difference.

I read it that because power doesn't vary much with crank length that crank length "CAN BE CHOSEN TO MEET OTHER CRITERIA" of which aerodynamics is one, where he states shorter is better. Now, of course, I am sure someone will be able to find an exception to this generality which is why I have stressed experimenting with this.

 

[onetrack]

Only if the rider can improve their aerodynamic position. And there are more ways to improve aerodynamic position than changing crank length.

That's like saying there are ways to improve aerodynamic position other than using tt bars. no ****. But you get bigger reductions in drag, and more power from shortening the cranks and the resulting compact position, and the ability to hold position longer. No reduction in leverage if geared properly.

If you actually had experience with this thing you adamantly oppose you'd know all these advantages hold true. Not sure what you hope to gain by saying something doesn't work when you have zero experience with it. Go ahead, follow the leader like I'm sure you do with the rest of your coaching practice.

 

[CoachFergie]

I read it that because power doesn't vary much with crank length that crank length "CAN BE CHOSEN TO MEET OTHER CRITERIA" of which aerodynamics is one, where he states shorter is better. Now, of course, I am sure someone will be able to find an exception to this generality which is why I have stressed this.

Power doesn't vary till you go stupid short and stupid long and if one needed to work on aerodynamics there are a variety of manipulations including crank length. I tilted my saddle up two millimetres and was able to drop my bars down 4cm.

 

[CoachFergie]

That's like saying there are ways to improve aerodynamic position other than using tt bars. no ****. But you get bigger reductions in drag, and more power from shortening the cranks and the resulting compact position, and the ability to hold position longer. No reduction in leverage if geared properly.

You saying that as if you think if you will repeat it often enough it will make it true.

To recap...

Shorter cranks do not increase power. They never will, just like independent cranks, power meters, aero wheels, nasal strips, high carbohydrate diets.

If you actually had experience with this thing you adamantly oppose you'd know all these advantages hold true. Not sure what you hope to gain by saying something doesn't work when you have zero experience with it.

That's a stupid assertion. Do I need to smoke for years to be able to say it's bad?

Have a look at this list of biases and see how many you can put a tick beside

Go ahead, follow the leader like I'm sure you do with the rest of your coaching practice.

As a coach I wouldn't want to work with someone who needs a gimmick to train and has so much self doubt in their own abilities that they believe they need to buy speed and power.

But if I wasted a Grand on a product that claimed to improve power and didn't I would display a high level of cognitive dissonance as well

 

[FrankDay]

I tilted my saddle up two millimetres and was able to drop my bars down 4cm.

Good for you. How long can you hold that position? Did the change do anything to your FTP? Can you theorize why tilting the saddle up facilitates your ability to get lower or, why couldn't you make this change before?

 

[CoachFergie]

Good for you. How long can you hold that position? Did the change do anything to your FTP? Can you theorize why tilting the saddle up facilitates your ability to get lower or, why couldn't you make this change before?

3 hours so far. Getting into summer here so will go for longer. It opens up the hip angle and removed the rounding I had in the lower back. Not bad for a 50c allen key and a 10 sec adjustment.

 

[FrankDay]

3 hours so far. Getting into summer here so will go for longer. It opens up the hip angle and removed the rounding I had in the lower back. Not bad for a 50c allen key and a 10 sec adjustment.

How does "tilting the saddle" open the hip angle. Especially, tilting the saddle 2 mm? Isn't hip angle determined by the contact points geometry? What does the tilt of the saddle have to do with that?

 

[CoachFergie]

Then I must have changed my points of contact then. I have posted the before and after pics before, you even commented on them, which clearly show the difference.

Just goes to show there are cheaper and easier ways to improve aerodynamics.

 

[FrankDay]

Then I must have changed my points of contact then. I have posted the before and after pics before, you even commented on them, which clearly show the difference.

Just goes to show there are cheaper and easier ways to improve aerodynamics.

I must have missed those pictures. Could you give us a link to them again please?

So, I don't understand why tilting the saddle 2mm would change your contact points enough to allow you to drop your handlebars 4 cm? Any thoughts as to what is occurring? Or, were you just poorly fit before?

Oh, and you haven't told us what this change has done to your FTP?

 

[CoachFergie]

I must have missed those pictures. Could you give us a link to them again please?

So, I don't understand why tilting the saddle 2mm would change your contact points enough to allow you to drop your handlebars 4 cm? Any thoughts as to what is occurring? Or, were you just poorly fit before?

Oh, and you haven't told us what this change has done to your FTP?

You didn't miss them, you commented on them.

It hasn't affected my ability to produce power.

 

[FrankDay]

You didn't miss them, you commented on them.

It hasn't affected my ability to produce power.

Well, I must have forgotten about them. Could you give a link or, if they are in this thread, give me a post number so I (and everyone else) doesn't have to slog through almost a 1000 posts to find them. (Edit: I found in post 148 where I also asked for pictures but I could not find you responding to that request. Could you please direct me to your response. Thanks)

Anyhow, you haven't said how you think that 2mm tilting up of the saddle allows one to lower the handlebar 4cm. I am still intrigued by the mechanism of this.

If it hasn't affected your power and you have lowered your front end 4 cm, what has this done to your speed?

 

[Night Rider]

I am really confused here as to what you took from any Martin study that suggests he is giving a finding of an optimum crank length/leg length ratio. Most of the stuff I have found he suggests crank length has very little effect on power, efficiency or, almost, anything else. So, even though power was highest with shorter cranks, Martin concluded the effect was so small people could use pretty much whatever crank length they wanted without losing much.

Copied from the study.

The selection of optimal cycle crank length for max- imal power production may be of interest to competitive cyclists and to researchers who use cycle ergometry as a laboratory-based performance measure. Our data dem- onstrate that the optimal crank length for maximal power was 20% of leg length or 41% of tibia length. For our subjects, the mean optimal crank length calculated as a proportion of leg length [169 (2) mm] was similar to that calculated as a proportion of tibia length [170 (3) mm]. Both of these are quite similar to the standard length of bicycle and ergometer cranks (170 mm). Op- timal crank length (i.e., 20% of leg length) varied from 151 mm for our shortest-legged (75.7 cm leg length) subject to 183 mm for our longest-legged subject (91.4 cmleg length). Even though the range in optimal crank length of our subjects was 32 mm, the regression equa- tion (Fig. 3) indicated that standard (170 mm) length cranks would reduce power by less than 0.5%. Thus, standard laboratory or bicycle equipment should not substantially compromise maximum power for most adults.
The optimal length determined from this investiga- tion agrees well with that reported by Inbar et al. (1983: 166 mm). Indeed, even though the methods employed by Inbar et al. (1983) were quite different from those used in the present study, the results are qualitatively similar.

And yes, it was discussed about a 90 pages back that the difference was .5 percent between optimal and the end points of the range (range = 32mm).

Now going back to my post, I would have stuck with my 172.5mm's even if my 'optimal' measured crank length was 170mm or 175mm. The data suggests it would make little to no difference, hell, I would get much higher gains from refining and improving my training. And that is pretty much the crux of the argument "the importance of crank length to the cyclist".

There are much more important things in my opinion, most cyclists are probably on near enough to their optimal cranks lengths, and even if they aren't the difference is immaterial anyway.

 

[Night Rider]

not to agree or disagree with anyone here but I am sure what Mr. Day was doing in his post was the use of an analogy to help support his position.

Trying to do. It was a flawed analogy and that's why it's easy to pick holes in it. I'm not going to be responsible for sidetracking the discussion down that path though. We would all be here for another six months debating that!

 

[CoachFergie]

And yes, it was discussed about a 90 pages back that the difference was .5 percent between optimal and the end points of the range (range = 32mm).

Hopkins discusses meaningful differences in performance and sadly .5% (and that is only for the very short and the very tall, less for others) potential improvement is not meaningful.

Now going back to my post, I would have stuck with my 172.5mm's even if my 'optimal' measured crank length was 170mm or 175mm. The data suggests it would make little to no difference, hell, I would get much higher gains from refining and improving my training. And that is pretty much the crux of the argument "the importance of crank length to the cyclist".

All the formulas have indicated I should ride 172.5mm but I have never liked them and use 170mm and have never bothered changing my track cranks from 165mm. Possibly because I ride a high cadence I am suited to a shorter crank than the formula suggests.

Training you say! Why train when you can buy speed?

There are much more important things in my opinion, most cyclists are probably on near enough to their optimal cranks lengths, and even if they aren't the difference is immaterial anyway.

Or so the research would indicate. But if that fails you just go by subjective feelings.

 

[FrankDay]

Copied from the study.

Our data demonstrate that the optimal crank length for maximal power was 20% of leg length or 41% of tibia length.

I might point out that the study only looked at one rev max power and did not look at sustainable power for any period of time nor did it look at any of the other dependent outcomes (such as aerodynamics or comfort or efficiency) that could also be affected by crank length. If that is all you care about, maximum power, then by all means use that study as your source.

And yes, it was discussed about a 90 pages back that the difference was .5 percent between optimal and the end points of the range (range = 32mm).

Now going back to my post, I would have stuck with my 172.5mm's even if my 'optimal' measured crank length was 170mm or 175mm. The data suggests it would make little to no difference, hell, I would get much higher gains from refining and improving my training. And that is pretty much the crux of the argument "the importance of crank length to the cyclist".

Why wouldn't you want to do both? It isn't like you have to choose one over the other.

There are much more important things in my opinion, most cyclists are probably on near enough to their optimal cranks lengths, and even if they aren't the difference is immaterial anyway.

Only if the only thing you care about is power. And, I would substitute small for immaterial. Anyhow, apparently, once one owns a power meter they seem to forget about everything else.

 

[CoachFergie]

I might point out that the study only looked at one rev max power and did not look at sustainable power for any period of time nor did it look at any of the other dependent outcomes (such as aerodynamics or comfort or efficiency) that could also be affected by crank length. If that is all you care about, maximum power, then by all means use that study as your source.

Comical. McDaniel looked at efficiency and found no significant differences.

Only if the only thing you care about is power. And, I would substitute small for immaterial. Anyhow, apparently, once one owns a power meter they seem to forget about everything else.

That is pathetic. When one purchases a power meter they become more aware of what actually determines performance. Seeing the maximum potential advantage from the shortest and the tallest person riding a 170mm crank is 0.5% you would need a pretty good power meter to actually measure any difference due to a change in crank length alone.

 

[FrankDay]

Comical. McDaniel looked at efficiency and found no significant differences.

Here are a few of my problems with this analytical outcome. The study Nightrider says he used did not look at efficiency. It looked at 1 rev max power. This study came up with an optimum crank length of 41% of tibia length as being optimum. I presume from this there is no standard deviation, this number is best for everyone.

Then, in the very same abstract he copied we have this

The optimal length determined from this investigation agrees well with that reported by Inbar et al. (1983: 166 mm).

Now Inbar looked at best crank length for 30 second efforts and got a somewhat shorter optimum length. And, of course, if he had looked at it we can presume he would have determined a different tibia ratio for a 30 second effort because he found a different optimum crank length.

Now, what does a study that looks at optimum crank length for 1 revolution max power or 30 second max power say about optimum crank length for 5 minutes, or 5 hours?

And, then again, these studies only looked at power. Even the author of one of the studies concludes that crank length affects other aspects of cycling (most importantly to him aerodynamics, and ground clearance) that needs to be taken into account.

When one is looking for help choosing an optimum crank length for a 2-5 hour effort why on earth would one use a study that looks at one rep power and ignores other important aspects that should be considered as the only source. It makes little sense to me.

It goes to the entire reason for this post. It is quite clear crank length affects many aspects of cycling and the best crank length is the one that gives the best combination of power, aerodynamics, fatigue, and comfort for that individual. I simply do not see how there could be a one size fits all formula for determining this in view of the wide variation in cyclists and the wide variation of racing these cyclists do. IMHO, the only way to know what is best for you is to experiment and find out.

 

[CoachFergie]

Here are a few of my problems with this analytical outcome. The study Nightrider says he used did not look at efficiency. It looked at 1 rev max power. This study came up with an optimum crank length of 41% of tibia length as being optimum. I presume from this there is no standard deviation, this number is best for everyone.

That is not what they said in Martin (2001). They said that from their data 41 was the optimal percentage of leg length for crank length. This number was not suggested as optimal for everyone.

Then, in the very same abstract he copied we have this
Now Inbar looked at best crank length for 30 second efforts and got a somewhat shorter optimum length. And, of course, if he had looked at it we can presume he would have determined a different tibia ratio for a 30 second effort because he found a different optimum crank length.

Martin (2001) didn't suggest an optimal crank length.

I don't have access to the full Inbar study but reading the abstract I would suggest that 164-166mm is not somewhat shorter than the 175mm they suggested was the standard crank length. The abstract states that running 175mm will at worst affect power by 1.24%. Again a mountain out of a molehill.

Now, what does a study that looks at optimum crank length for 1 revolution max power or 30 second max power say about optimum crank length for 5 minutes, or 5 hours?

The Martin (2001) didn't intend to look at optimal crank length for anything beyond maximal power production. The McDaniel and Thomas studies looked at that and determined that efficiency and fatigue were not affected by crank length.

And, then again, these studies only looked at power. Even the author of one of the studies concludes that crank length affects other aspects of cycling (most importantly to him aerodynamics, and ground clearance) that needs to be taken into account.

Again the fallacy that crank length is the only intervention possible that will change aerodynamics and ground clearance.

It goes to the entire reason for this post. It is quite clear crank length affects many aspects of cycling and the best crank length is the one that gives the best combination of power, aerodynamics, fatigue, and comfort for that individual. I simply do not see how there could be a one size fits all formula for determining this in view of the wide variation in cyclists and the wide variation of racing these cyclists do. IMHO, the only way to know what is best for you is to experiment and find out.

The research has been done it shows that there is no importance of crank length. If cyclists want to improve their performance there are far more effective, practical and time efficient ways than experimenting with crank length.

 

[onetrack]

Shorter cranks do not increase power. They never will, just like independent cranks, power meters, aero wheels, nasal strips, high carbohydrate diets.

As a coach I wouldn't want to work with someone who needs a gimmick to train and has so much self doubt in their own abilities that they believe they need to buy speed and power.

great. you can show me then a cyclist who did not improve with a substantially shorter crank. "and never will"

Well that works out perfect for me, because as a cyclist, I don't want to work with a coach who is uninterested in finding my perfect position and crank length Before sending me out to train with a sub optimal setup.

Shorter cranks don't make you fast, cranks that are too long make you slow. if you actually had any experience with this thing you adamantly oppose, you'd see that.