The importance of crank length to the cyclist.

[FrankDay]

I think he's saying overall there is a wattage drop going into the " rather extreme aero position" that short cranks can't overcome (though he can squeeze out another 5).

I read that as he increased his wattage 5 watts but that he saw increased drag from shorter cranks. Increased drag makes no sense to me. Perhaps he can clarify.

 

[Oldman]

Your evidence for the kind of experimenting they did and the results?

Do you look in the mirror when you say this stuff? I rode with them, in cars behind them and in TTT's with many of them. As for Cancellara, Miguel, Eddie; I presume they had the same opportunities.
I asked them to try different sizes and our sponsors gave them to us. I actually talked guys into using shorter cranks until we hit an optimal level. Guess what? It was nowhere below 170cm.

 

[FrankDay]

Do you look in the mirror when you say this stuff? I rode with them, in cars behind them and in TTT's with many of them. As for Cancellara, Miguel, Eddie; I presume they had the same opportunities.
I asked them to try different sizes and our sponsors gave them to us. I actually talked guys into using shorter cranks until we hit an optimal level. Guess what? It was nowhere below 170cm.

Cool. I would like to see the data that suggests that you achieved optimal level (performance would have shown an inverted U shape) but as long as those athletes experimented and decided what was best for them then I am cool with it (although my own experience is these elite athletes really are not interested in doing much real experimenting).

However, just because their results were longer than 170 is not evidence that such lengths are best for me or anyone else reading this thread.

 

[CoachFergie]

No evidence

perhaps not the evidence you prefer

personal experience is plenty

Tell us again how much personal experience you have with very short cranks.

Yes no evidence at all. Not even one power meter file has been presented showing that using a shorter crank has improved performance and shown that it was the shorter crank that led to the performance.

Your personal experience is meaningless. You have no way to verify what caused any changes if the changes really happened at all.

I don't need personal experience when I can read Martin, McDaniel's and other studies and the data shows there is no significant "importance" of crank length.

Mind you if I dropped a Grand on a product that claimed to improve performance (are you 40% better from using independent cranks) but had no real evidence and the best I could do was some "cool stories Bro" then I assume I would display a little cognitive dissonance myself.

Alice jumped on her track bike tonight going from 172.5mm road cranks to 165mm track cranks and was soundly beaten by the girls she had beaten on the weekend. Pitched at your level of evidence I can only conclude that short cranks suck

 

[oldborn]

Proud to Be on your ignore list

P.S. Buy a dog!

 

[blutto]

A THOUGHT FOR TODAY:
Pedantry and mastery are opposite attitudes toward rules. To apply a rule to the letter, rigidly, unquestioningly, in cases where it fits and in cases where it does not fit, is pedantry ... To apply a rule with natural ease, with judgment, noticing the cases where it fits, and without ever letting the words of the rule obscure the purpose of the action or the opportunities of the situation, is mastery. -George Polya, mathematician (1887-1985)

Cheers

blutto

 

[acoggan]

I'll match my results against yours any time. 52:20 40km at 45 years of age and not a pro. 135lbs body weight.

51:52 @ 50 y of age. Also a skinny non-pro.

 

[acoggan]

so, if I'm understanding you correctly. In an aero position you make more power on 148mm cranks. But overall you made the most power in a more upright position.

Correct. Also, my drag is lower in the more extreme position, but even w/ 148 mm cranks my power:drag is higher in a higher position (under UCI rules, anyway).

Did you test the shorter cranks in a more upright position?

I tested each of 3 crank lengths (i.e., 148, 165, and 170 mm) in each of 4 positions. Shorter cranks were only of benefit when I was way bent over.

 

[FrankDay]

Correct. Also, my drag is lower in the more extreme position, but even w/ 148 mm cranks my power:drag is higher in a higher position (under UCI rules, anyway).

I tested each of 3 crank lengths (i.e., 148, 165, and 170 mm) in each of 4 positions. Shorter cranks were only of benefit when I was way bent over.

Well, a little more detail regarding your protocol (to help us draw our own conclusions) would be useful here.

1. did you spend any time adapting to each length?
2. What basic changes did you make to the bike (seat, handlebars) when you changed crank length before you made your position changes.
3. what were the 4 positions? (do you have pictures?)
4. Did you control for cadence or pedal speed as you changed crank length?
5. How many runs in each combination?
5. What was your actual data for these runs? (It doesn't make obvious sense to me that your power could be up on the shortest crank and your drag could be down but your power/drag was best in a more upright position, apparently on longer cranks.)

 

[acoggan]

Well, a little more detail regarding your protocol (to help us draw our own conclusions) would be useful here.

1. did you spend any time adapting to each length?
2. What basic changes did you make to the bike (seat, handlebars) when you changed crank length before you made your position changes.
3. what were the 4 positions? (do you have pictures?)
4. Did you control for cadence or pedal speed as you changed crank length?
5. How many runs in each combination?
5. What was your actual data for these runs? (It doesn't make obvious sense to me that your power could be up on the shortest crank and your drag could be down but your power/drag was best in a more upright position, apparently on longer cranks.)

1. Weeks to years, depending on the length.
2. I kept leg extension and position relative to the b.b. constant.
3. I tested saddle-to-elbow-pad distances of 14%, 22%, 28%, and 33% of my saddle-to-b.b. distance. Pictures can be found all over the web.
4. Cadence was self-selected.
5. I did 2-3 20 min efforts using each crank length.
6. I'll have to dig it up, but the bottom line is that as I lower my aerobars, power decreases more rapidly than drag, such that power:drag goes down. The reduction in power is slightly mitigated by using 148 mm cranks, but at least under UCI rules my power:drag is still higher when using a more upright position, in which case I don't need shorter cranks.

 

[acoggan]

Pictures can be found all over the web.

My current position:

Next lower:

Lower still:

Lowest of all:

Note that the last picture was when I was testing John Cobb's "low sit" position, with my saddle well below normal. I kept the saddle-to-aerobar distance the same, however, so the angle of my torso is what is of relevance here.

 

[FrankDay]

1. Weeks to years, depending on the length.
2. I kept leg extension and position relative to the b.b. constant.
3. I tested saddle-to-elbow-pad distances of 14%, 22%, 28%, and 33% of my saddle-to-b.b. distance. Pictures can be found all over the web.
4. Cadence was self-selected.
5. I did 2-3 20 min efforts using each crank length.
6. I'll have to dig it up, but the bottom line is that as I lower my aerobars, power decreases more rapidly than drag, such that power:drag goes down. The reduction in power is slightly mitigated by using 148 mm cranks, but at least under UCI rules my power:drag is still higher when using a more upright position, in which case I don't need shorter cranks.

Thanks. A couple of comments.

1. Not sure by what you mean you spent weeks to years adapting to each length. How is is possible to do such a test over such a long period of time?

2. Your drop was not the same for the 4 positions with the different crank lengths. As you raise your seat to accommodate the leg extension fit as you shortened the cranks, the seat to BB distance would change so that would mean your drop was greater for the shorter cranks than it was for the longer cranks because you were using a percentage of this distance. Despite this, your power drop was mitigated as you got lower with shorter cranks. Perhaps you might have gotten a different result if you had kept the absolute drops the same for the various crank lengths.

3. Your data supports my contention that power drops as the rider lowers the torso. What do you think of Alex's contention that his rider actually had his maximum power in that scrunched up position.

 

[acoggan]

Thanks. A couple of comments.

1. Not sure by what you mean you spent weeks to years adapting to each length. How is is possible to do such a test over such a long period of time?

Lots of patience?

By "years", I was alluding to the fact that I trained and raced on 170 (and 172.5 and 175) mm cranks for a long time before I started experimenting with shorter cranks in the early/mid 1990s (at Jim Martin's suggestion, who started down this path in the late 1980s).

2. Your drop was not the same for the 4 positions with the different crank lengths.

Actually, it was (at 10, 16, 20, and 24 cm). The only reason that I expressed the distance as a percentage of saddle height was to help others place things in better context. In doing so, though, I implied something I didn't mean to.

3. Your data supports my contention that power drops as the rider lowers the torso.

Well no surprise there, really...everyone has their limit.

What do you think of Alex's contention that his rider actually had his maximum power in that scrunched up position.

If Alex says that is true, then I believe him (because I know that he's measured it with a - tada! - powermeter, and isn't just guessing). As for why that is true, I'd just chalk it up to individual differences as a result of nature and/or nurture (e.g., cyclists and speedskaters have been shown to have the joint angle-force relationship of their hip extensors shifted to a more acute angle compared to untrained persons).

 

[FrankDay]

My current position:

Looks good, Would like to see a comparative picture with your pedals at near TDC (highest knee point) comparing long cranks and short cranks to see what happened to your hip angle.

Next lower:

Why are your elbows so much further forward in this position. Looks like you are reaching.

Lower still:

What seems to be happening here is as you go lower you raise your head more. This raising of the head would increase frontal area and prevent the drag from dropping as much as one would expect from a lower front, if all else were equal. Could this be affecting the results.

Lowest of all:

Note that the last picture was when I was testing John Cobb's "low sit" position, with my saddle well below normal. I kept the saddle-to-aerobar distance the same, however, so the angle of my torso is what is of relevance here.

Again, high head, which would affect drag.

Also, you didn't test in this position did you, as the dynamics certainly cannot be considered the same? You are using this only as an example of the drop?

Thanks for the pictures.

 

[FrankDay]

If Alex says that is true, then I believe him (because I know that he's measured it with a - tada! - powermeter, and isn't just guessing). As for why that is true, I'd just chalk it up to individual differences as a result of nature and/or nurture (e.g., cyclists and speedskaters have been shown to have the joint angle-force relationship of their hip extensors shifted to a more acute angle compared to untrained persons).

Well, you certainly are a trained cyclist and the shift hasn't occurred for you. Perhaps his rider is an outlier. I don't know. I understand you trust him but don't you think, as a scientist, it would be good to see the raw data. Even friends can make mistakes, don't you think? Either way, I would like to see the raw data. If true, I would like to be able to explain exactly what the difference in these riders to cause such an astonishing difference. Don't you think such an understanding would help bike fitters in the future?

 

[Alex Simmons/RST]

Not quite crank lengths, but a recent study published on the effect of aero vs upright position on trained endurance females:

http://www.tandfonline.com/doi/abs/10.1080/15438627.2011.608039

I don't have ready access to full text so can't say I've examined it in any detail.

Eighteen females participants (VO2max 49.7 ± 6.3 ml·kg−1·min−1) all with competitive experience performed cycling trials at ventilatory threshold 1 and 2 (VT-1, VT-2) in both an aerodynamic and an upright position. There was a significant difference in PO between the aerodynamic and upright positions at VT-1 (152.7 ± 28.0 Watts and 159.7 ± 33.1 Watts, respectively) but not at VT-2 (191.2 ± 39.1 Watts and 192.4 ± 40.0 Watts, respectively). There were no significant differences in heart rate, oxygen consumption, or cadence between positions at either intensity. At both intensities the individual response was varied and no trends due to years of experience or background (triathlete or cyclist) explained this variability. Therefore, despite the significant mean difference in PO at VT-1, these results indicate that in trained females the effect of aerodynamic positioning is individual.

 

[FrankDay]

Not quite crank lengths, but a recent study published on the effect of aero vs upright position on trained endurance females:

http://www.tandfonline.com/doi/abs/10.1080/15438627.2011.608039

I don't have ready access to full text so can't say I've examined it in any detail.

Eighteen females participants (VO2max 49.7 ± 6.3 ml·kg−1·min−1) all with competitive experience performed cycling trials at ventilatory threshold 1 and 2 (VT-1, VT-2) in both an aerodynamic and an upright position. There was a significant difference in PO between the aerodynamic and upright positions at VT-1 (152.7 ± 28.0 Watts and 159.7 ± 33.1 Watts, respectively) but not at VT-2 (191.2 ± 39.1 Watts and 192.4 ± 40.0 Watts, respectively). There were no significant differences in heart rate, oxygen consumption, or cadence between positions at either intensity. At both intensities the individual response was varied and no trends due to years of experience or background (triathlete or cyclist) explained this variability. Therefore, despite the significant mean difference in PO at VT-1, these results indicate that in trained females the effect of aerodynamic positioning is individual.

On the face of it it looks interesting. While not directly related to crank length it does go to what has been discussed here. It would have been nice if they had done some flexibility tests on their subjects to see if there were any correlations there. Something has to explain why these effects are "individual".

 

[acoggan]

Well, you certainly are a trained cyclist and the shift hasn't occurred for you.

"Objection, Your Honor: assumes facts not in evidence."

(Think about it a bit, and you should understand.)

 

[acoggan]

Why are your elbows so much further forward in this position.

The pic was taken before I shortened my reach to be UCI legal. The drop in that pic, though, is 16 cm, and I measured my drag (and power) using the shorter reach.

What seems to be happening here is as you go lower you raise your head more. This raising of the head would increase frontal area and prevent the drag from dropping as much as one would expect from a lower front, if all else were equal. Could this be affecting the results.
Again, high head, which would affect drag.

Head position is obviously important. That's why I've done field tests using my powermeter to try to determine the best way to hold my head (while still being able to see far enough down the road).

Also, you didn't test in this position did you, as the dynamics certainly cannot be considered the same? You are using this only as an example of the drop?

Actually, I measured both my sustainable power and my drag in the "low sit" position as well (again, using my powermeter...handy things, those). For the purposes of the present discussion, though, the only point in sharing the pic is to illustrate what effect having the elbow pads 24 cm below the saddle has upon the position of my upper body.

 

[FrankDay]

Head position is obviously important. That's why I've done field tests using my powermeter to try to determine the best way to hold my head (while still being able to see far enough down the road).

Cool, except for all things being equal the head must be in the same position. It can't be below the shoulders in one trial and above in another or you haven't learned anything about the effect of the position on drag. It isn't clear to me that you have done this such that your results are meaningful towards this discussion. All else being equal a smaller frontal area should result in less drag and a lower front should result in a lower frontal area.

 

[acoggan]

for all things being equal the head must be in the same position. It can't be below the shoulders in one trial and above in another or you haven't learned anything about the effect of the position on drag.

Uh, no: head position is (readily) influenced by elbow pad height, i.e., you can't (necessarily) dissociate the two.

More specifically in my case, when testing I kept my head as low as possible while 1) still being able to see far enough down the road that I felt comfortable that I wasn't going to crash into something, and 2) keeping the tail of the helmet in contact with my back. (Note that since the pics were taken at different times/for different reasons, they don't necessarily reflect how I held my head when measuring my drag or power.)

To state it another way: the reason that my drag only decreased slightly once I moved beyond 10-16 cm of drop might be because I can't "turtle" as well as I can in a higher position. OTOH, it might be due to other reasons, e.g., exposure of more of my upper back to the wind (as John Cobb has theorized). Short of cutting off my head, though, there really is no way of distinguishing between these possibilities, so it the point is moot.

 

[FrankDay]

Uh, no: head position is (readily) influenced by elbow pad height, i.e., you can't (necessarily) dissociate the two.

More specifically in my case, when testing I kept my head as low as possible while 1) still being able to see far enough down the road that I felt comfortable that I wasn't going to crash into something, and 2) keeping the tail of the helmet in contact with my back. (Note that since the pics were taken at different times/for different reasons, they don't necessarily reflect how I held my head when measuring my drag or power.)

To state it another way: the reason that my drag only decreased slightly once I moved beyond 10-16 cm of drop might be because I can't "turtle" as well as I can in a higher position. OTOH, it might be due to other reasons, e.g., exposure of more of my upper back to the wind (as John Cobb has theorized). Short of cutting off my head, though, there really is no way of distinguishing between these possibilities, so it the point is moot.

Well, without pictures we have no way of confirming that your head was similar for the different trials. I think that everyone can see from the pictures that it is a possibility that this is an issue. The lower the front end the less "turtle" should be needed to keep the head below the highest part of the back.

Oh, and BTW, IMHO, your "high" position is much lower and better than most peoples "low" position. So, it is not clear to me that your data has much application to the masses. Once the head is below the back it is not clear to me there is much benefit, if any, to going lower. That may be all your data reflects.

 

[Oldman]

51:52 @ 50 y of age. Also a skinny non-pro.

Excellent work. You clearly understand that the experimentation inevitably is individual. My contention with "short crank" advocates is the same argument I had with teammates, riders that felt long cranks were the answer.

 

[Captain Serious]

2. I kept leg extension and position relative to the b.b. constant.
.

I gather this means you adjusted the saddle height to get the same leg reach/knee extension at the bottom of the pedal stroke, or did you adjust the saddle height relative to the bb? If you had the same reach through bottom of the stroke, was it then that you produced less power with the shorter cranks? Hmm, interesting.

Thanks

 

[Captain Serious]

Since reading this stuff about shorter cranks, I've scored some cheap 165s (9sp105s), 167.5s (9sp Dura-Ace), and some 7800 DA 170s. I'll probably get some more 165s, if I find some 7800s cheap enough. I'm currently racing on the 170s (I haven't yet had the guts to race on the 165s), and have had some results recently via some short solo attacks, and I'm gunna credit it to my knew 'aero' position, due to the shorter cranks. Man, I reckon I look like De Vlaeminck out there (see below).

For the casual viewers, a refresher: I'm 181cm (i've shrunk) with an 89cm inside leg, and I've used everything from 172.5 to 180s in the last 5 to 7 years.

I've been training mostly on the 165s and 167.5s, partly because I have a minor knee injury (the reduced flexion with the shorter cranks seems to help). I've decided I'm not gunna bother trying anything shorter than 165s (unless all the pros start doing it ), partly because lengths shorter than this tend to only be available in 'boutique', trickier-to-get brands, and, well, I figure 165 is short enough to serve the purpose of getting me much more aero (coz my thighs don't hit my tummy).

Does anyone think that the reduced hip angle at the top of the stroke, produced by using shorter cranks could improve lower back pain? Using shorter cranks has coincided with my back pain improving, even though I've been bending over more on the bike. Either that, or it's all the fish oil I've been taking.