The importance of crank length to the cyclist.

[FrankDay]

Does anyone think that the reduced hip angle at the top of the stroke, produced by using shorter cranks could improve lower back pain?

Yes. because I have heard this from others. And, shouldn't it be described as an increased (more open) hip angle at TDC?

 

[onetrack]

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.

I've never had bad back pain, but occasional soreness. Nevertheless, I too found it more comfortable in the new more aggressive short crank position. At first I thought it was because of the hip angle. But now, I think it is because it allows your pelvis to roll forward without thigh/rib interference. This reduces the extreme bend in your spine as you get down and aero. Judging by his youtube videos, John Cobb seems to agree with this finding.

 

[Captain Serious]

Thanks.
I'll check out some Cobb Youtubes

 

[Captain Serious]

Yes. because I have heard this from others. And, shouldn't it be described as an increased (more open) hip angle at TDC?

Oops. Maybe I should've said 'reduced hip flexion'

 

[FrankDay]

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…

If you ever want to try something shorter but want to stay with what you have brand-wise consider this http://www.bikesmithdesign.com/Short_Cranks/shorten.html

 

[Captain Serious]

Thanks. I've never heard of that.
I also never knew that Shimano Hollowtech cranks have got steel 'tongues'
http://www.bikesmithdesign.com/Short_Cranks/hollow.html

 

[FrankDay]

Well, I guess there is a limit as to how short you can go. Here is the latest report from Drew:

103 mile El Cajon Julian r///de. rode 80s up to julian then switched to 90s for the return. 90s felt better to me and i think this my lower limit right now on the short crank planet. Think 80-90 good for short riders and time trials. 100 mm good for general road riding and 110-120 for the taller riders and climbing and mtb

He later wrote:

I think i bottomed out at the 80s and the 90s feel better. feel like i can muscle the gear if i want to. also on 80s my heart rate was low proably becuase i could not tax the needed muscles enough. almost like arm wrestling with my pinkie. felt strenous buit heart rate would remain low.

It is interesting that I found about the same limit. 85 was definitely too short for me. Anyhow, he is just now getting a powertap. Maybe we will be able to document for those of you who need this his feelings have a "real" basis.

 

[CoachFergie]

It is interesting that I found about the same limit. 85 was definitely too short for me. Anyhow, he is just now getting a powertap. Maybe we will be able to document for those of you who need this his feelings have a "real" basis.

Be sure to let us know how he differentiates between performance changes in power due to short cranks, independent cranks, training, diet, recovery and what colour socks he wore?

I have a rider who was set up on his track bike and advised to drop from 172.5mm cranks to 170mm cranks. I suggested this would make ****** all difference. He went on to win two medals at Junior Worlds in Moscow. Maybe it was the crank length, maybe it was his starting training with a power meter in May? We can rule out sock colour as he went no socks for both medal winning rides.

 

[Alex Simmons/RST]

We can rule out sock colour as he went no socks for both medal winning rides.

Excellent. I'm going to suggest my riders go sans-socks for major events. The evidence is clear.

 

[FrankDay]

While not looking at a wide range of sizes this study does find a racing advantage to shorter cranks.

From the abstract: "The time to reach supra-maximal peak power was significantly (P<0.05) shorter in the 170 mm (2.57 ± 0.79 s) condition compared to 175 mm (3.29 ± 0.76 s). This effect represented a mean performance advantage of 27.8% for 170 mm compared to 175 mm. … The decreased time to peak power with the greater rate of power development in the 170 mm condition suggests a race advantage may be achieved using a shorter crank length than commonly observed. Additionally, there was no impediment to either power output produced at low cadences or indices of endurance performance using the shorter crank length and the advantage of being able to respond quickly to a change in terrain could be of strategic importance to elite athletes."

 

[CoachFergie]

While not looking at a wide range of sizes this study does find a racing advantage to shorter cranks.

Nice bit of selective reporting there.

Why not include this section of the abstract...

There was no further intercondition differences between performance outcome measurements derived for the isokinetic (50 rpm) maximum power output, isokinetic (50 rpm) mean power output or indices of endurance performance.

For a two hour MTB race endurance performance is a tad more important than time to peak power.

 

[FrankDay]

Nice bit of selective reporting there.

Why not include this section of the abstract...

Well, I did link to the entire abstract such that it was easy for everyone to get and the reason for the post was to highlight the differences, not the sameness, of their finding so I highlighted that.

For a two hour MTB race endurance performance is a tad more important than time to peak power.

OK, but don't you think this finding might have some bearing on other kinds of racing? Sometimes it is necessary to draw inferences beyond what the study showed exactly. In fact, when applying science to the real world, it is usually necessary to draw such inferences, in my experience. And, of course, you are free to ignore or interpret this however you desire. I simply point out that this study exists and it goes to the subject of this thread.

 

[FrankDay]

One more anecdotal report, this one from a coach.

I rode at 155mm length this week and was very surprised at how much I liked the shorter length and noticed both higher spin scan numbers and power output on my computrainer. Will try 135mm next week.

 

[CoachFergie]

OK, but don't you think this finding might have some bearing on other kinds of racing?

Not really unless there they include a 20 metre event at World Champs. What is interesting is that BMX riders (where the event is usually decided in the first 2-3 pedal strokes) typically use a 180mm crank.

Spin scan is a meaningless metric. I have several riders power profiles which show they have improved power without changing crank length and no comfort issues after a three day stage race last weekend.

 

[sciguy]

One of the really fantastic things that we'll certainly see from the paradigm shift that shorter cranks obviously represent is a wave of new hour records set by those with the foresight to embrace this new direction.

Here's one being set already:

Mike Nash accomplished a new record at 45.95 km for the hour (the old record was 45.187

Oops those look like conventional length cranks.......SRMs for that matter.... don't tell me the guy trained with power.........How 20th century of him

Hugh

 

[FrankDay]

One of the really fantastic things that we'll certainly see from the paradigm shift that shorter cranks obviously represent is a wave of new hour records set by those with the foresight to embrace this new direction.

Here's one being set already:

Mike Nash accomplished a new record at 45.95 km for the hour (the old record was 45.187

Oops those look like conventional length cranks.......SRMs for that matter.... don't tell me the guy trained with power.........How 20th century of him

Hugh

Take a look at that position. That fellow has so much room for aerodynamic improvement it is crazy. If he could do it without losing any or much power by going to a shorter crank length imagine what he might do.

The simple fact that older records were set with "long" crank lengths and that they have been broken with "long" crank lengths is not particularly good evidence that "long" crank lengths are better. Only when athletes of equivalent ability try these records on shorter cranks will we have an inkling of that.

 

[CoachFergie]

Professional Coaches and Sport Scientists would probably not draw such a conclusion based off just a photo.

 

[FrankDay]

Professional Coaches and Sport Scientists would probably not draw such a conclusion based off just a photo.

Who cares? It was my opinion. And, I would suggest that those trained in the profession of aerodynamics might agree more with me than your assortment of "professional coaches and sports scientists". But, again, that is just my opinion. LOL

 

[CoachFergie]

Those who are interested in evidence based practice probably would care. Any professional would require more than one photo to make an assessment on this chaps position, power delivery and whether short cranks may or may not offer any improvement.

 

[Oldman]

Those who are interested in evidence based practice probably would care. Any professional would require more than one photo to make an assessment on this chaps position, power delivery and whether short cranks may or may not offer any improvement.

That and the actual experience of what position allows you the physical ability to navigate a banked velodrome for an hour without biting the banking...My longer efforts in that position on a track was when I felt comfortable on 170mm rather than 165 or 167.5 cranks. My position was extremely low in all cases to the point where vision becomes the issue.

 

[Tapeworm]

Take a look at that position. That fellow has so much room for aerodynamic improvement it is crazy.

Eyeball aerodynamic assessment. Because that which looks aero, must be aero. How simple.

 

[Oldman]

Eyeball aerodynamic assessment. Because that which looks aero, must be aero. How simple.

Exactly. What is aero is the components of efficient speed. Look at a bike; it's not supposed to even stand up so how could it roll quickly?

 

[CoachFergie]

Also important to consider the angle the photo is taken from when eye-balling position.

What I have noted looking at photos and videos plus attending various top level track competitions where comfort is not an issue so if getting the torso lower than horizontal was an advantage these riders would do it. In particular the sprinters. I had heard the sprinters were trying 150mm cranks but this week they were all training and racing on 165-170mm, SRMs of course

 

[Alex Simmons/RST]

Mike Nash accomplished a new record at 45.95 km for the hour (the old record was 45.187

Oops those look like conventional length cranks.......SRMs for that matter.... don't tell me the guy trained with power.........How 20th century of him

Hugh

Nice work by Mike, and it will be well beaten before too long if I've got anything to do with it!

I'm looking to help a client add ~3.5km to that record.

 

[CoachFergie]

I'm looking to help a client add ~3.5km to that record.

By my calculations he will need to use a 106mm crank to do that