Retul fitting last night...

A light bike doesn't replace good fitness.

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KWalker
Posts: 5722
Joined: Mon Dec 28, 2009 8:30 pm
Location: Bay Area

by KWalker

Calnago wrote:@Kwalker, I don't get why a cyclist with as much riding experience as you seem to have would go for a Retul fit no less than 6 times, each with unsatisfactory results. At some point there is no better judge of proper fit than yourself, via experiment, trial and error, and knowledge gained over the years.

Which is why with the exception of my now custom orthotics and some tweaks to my cleat position it is precisely where I set it up myself.

The issue is that the Retul "assessment" only measures a few parameters of balance and flexibility. My recent and final fitter (who has fit dozens and dozens of current World Tour riders) has a background in physical therapy and kinesiology and had a far more extensive battery of tests including a way to measure bone lengths. Well, I had always said my right side felt a bit strange and turns out he was the only one that was able to locate which bone my LLD was in and adjust my shoe accordingly. Moreover he was the only one who actually had methods for diagnosing the source of my arch collapse and actually had the proper knowledge to fix my orthotics. Uncomfortable shoes went to awesome and changed my joint alignment and muscle recruitment, which required alterations in stance width and a lot of off the bike work to balance some muscular issues that had emerged from years of riding this way.

So basically since those fitters had zero background other than being bike shop guys who went to a class and applied some basic principles from said class they had no idea why my right side pedaled differently, why certain pains emerged out on the road, and why some of their metrics did not necessarily make sense given the tweaks they made. The difference was a 1cm higher higher saddle, 1cm narrower stance width per side, 1cm lower bars, 4mm further forward cleats and 5mm further rearwards saddle position. So, right where I put myself in the first place, but the Retul guys would see that my right side knee wasn't over the spindle and was overextending and would just move the seat down and forward until it fit, then widen my stance width to make my knees stable and inevitably raise my bars to match their perceived magical torso/joint angle. It resulted in a loss of power, knee injuries, and back issues.
Don't take me too seriously. The only person that doesn't hate Froome.
Gramz
Failed Custom Bike

TheKaiser
Posts: 653
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

KWalker wrote:
Calnago wrote:@Kwalker, I don't get why a cyclist with as much riding experience as you seem to have would go for a Retul fit no less than 6 times, each with unsatisfactory results. At some point there is no better judge of proper fit than yourself, via experiment, trial and error, and knowledge gained over the years.

Which is why with the exception of my now custom orthotics and some tweaks to my cleat position it is precisely where I set it up myself.

The issue is that the Retul "assessment" only measures a few parameters of balance and flexibility. My recent and final fitter (who has fit dozens and dozens of current World Tour riders) has a background in physical therapy and kinesiology and had a far more extensive battery of tests including a way to measure bone lengths. Well, I had always said my right side felt a bit strange and turns out he was the only one that was able to locate which bone my LLD was in and adjust my shoe accordingly. Moreover he was the only one who actually had methods for diagnosing the source of my arch collapse and actually had the proper knowledge to fix my orthotics. Uncomfortable shoes went to awesome and changed my joint alignment and muscle recruitment, which required alterations in stance width and a lot of off the bike work to balance some muscular issues that had emerged from years of riding this way.


How does this guy measure bone lengths? With Xray or similar scan, or some other method? I seem to have a functional LLD but am unsure if it is rooted in an actual difference in bone length, which is why I ask.

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DanW
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by DanW

You will struggle to find a true, *reliable* LLD from X-Ray. You might take some measurements and get some numbers but there so many sources of error that you'll never know for sure, unless it is huge... and in that case you've probably picked it up by other much more straight forward means or something jumps out in the person's history such as a fib/ tib fracture or similar. The dose from CT is hard to justify so that leaves MRI. I've worked with 3D bone models from MRI and these aren't fool proof either. Usually you'll be lucky to get a full tibia in the FOV and struggling to get the full femur in the FOV. You then have to register scan together and it all gets very messy. Do-able but there are only a handful of people who can do this accurately and repeatably and all of them are in the world of research. Even if you got around this some how with a massive FOV then the size of a voxel and the subsequent errors in taking measurements are in the region of a few mm which would be a massive % error. Basically, finding a true LLD is way outside the scope of a fit

I'd be inclined to not worry about the true length of the bones. Functional differences are functional differences.... which may need a degree of compensation and may have a degree of "treatability" over time. People are flippin' hard things to work with!

LionelB
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Joined: Sun Oct 05, 2008 8:09 pm
Location: Aix en Provence

by LionelB

Retul fit my a well know guy was the worst 300 euros I spent. He was recommending ridiculous radical changes purely base on a database of fit numbers. I went there because I had developed a back of the knee tendonitis that ended up having nothing to do with me fit.

Citizenfox
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Joined: Fri Apr 03, 2015 1:22 pm

by Citizenfox

YMMV

KWalker
Posts: 5722
Joined: Mon Dec 28, 2009 8:30 pm
Location: Bay Area

by KWalker

DanW wrote:You will struggle to find a true, *reliable* LLD from X-Ray. You might take some measurements and get some numbers but there so many sources of error that you'll never know for sure, unless it is huge... and in that case you've probably picked it up by other much more straight forward means or something jumps out in the person's history such as a fib/ tib fracture or similar. The dose from CT is hard to justify so that leaves MRI. I've worked with 3D bone models from MRI and these aren't fool proof either. Usually you'll be lucky to get a full tibia in the FOV and struggling to get the full femur in the FOV. You then have to register scan together and it all gets very messy. Do-able but there are only a handful of people who can do this accurately and repeatably and all of them are in the world of research. Even if you got around this some how with a massive FOV then the size of a voxel and the subsequent errors in taking measurements are in the region of a few mm which would be a massive % error. Basically, finding a true LLD is way outside the scope of a fit

I'd be inclined to not worry about the true length of the bones. Functional differences are functional differences.... which may need a degree of compensation and may have a degree of "treatability" over time. People are flippin' hard things to work with!

We used an MRI model, but the key point of interest was simply which bone was actually longer. For a tibial LLD you just shim the shoe, a femur LLD you can in some cases offset the cleat, but for both, well, that was the confounding part.

In the end though I used verifications other than Strava segments, which for some reason people still think is a valid analytics tool. Forget environmental conditions, rest, tire pressure, air pressure, and all those variables it doesn't actually take into account to compare times.
Don't take me too seriously. The only person that doesn't hate Froome.
Gramz
Failed Custom Bike

KheSanh
Posts: 40
Joined: Mon Apr 20, 2015 7:49 am
Location: Scotland

by KheSanh

I also had a Retul bike fit done at Velocity44 in Sterling Scotland. Well worth it, made quite a few changes and Paul and the guys there were great.

Citizenfox
Posts: 197
Joined: Fri Apr 03, 2015 1:22 pm

by Citizenfox

KWalker wrote:
DanW wrote:You will struggle to find a true, *reliable* LLD from X-Ray. You might take some measurements and get some numbers but there so many sources of error that you'll never know for sure, unless it is huge... and in that case you've probably picked it up by other much more straight forward means or something jumps out in the person's history such as a fib/ tib fracture or similar. The dose from CT is hard to justify so that leaves MRI. I've worked with 3D bone models from MRI and these aren't fool proof either. Usually you'll be lucky to get a full tibia in the FOV and struggling to get the full femur in the FOV. You then have to register scan together and it all gets very messy. Do-able but there are only a handful of people who can do this accurately and repeatably and all of them are in the world of research. Even if you got around this some how with a massive FOV then the size of a voxel and the subsequent errors in taking measurements are in the region of a few mm which would be a massive % error. Basically, finding a true LLD is way outside the scope of a fit

I'd be inclined to not worry about the true length of the bones. Functional differences are functional differences.... which may need a degree of compensation and may have a degree of "treatability" over time. People are flippin' hard things to work with!

We used an MRI model, but the key point of interest was simply which bone was actually longer. For a tibial LLD you just shim the shoe, a femur LLD you can in some cases offset the cleat, but for both, well, that was the confounding part.

In the end though I used verifications other than Strava segments, which for some reason people still think is a valid analytics tool. Forget environmental conditions, rest, tire pressure, air pressure, and all those variables it doesn't actually take into account to compare times.


Yeah, real world performance is over rated as an indicator of real world performance.

jeffy
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Joined: Sun Oct 05, 2014 11:51 pm

by jeffy

assuming an 8 degree stem. surprising that you are an inch higher and an inch shorter, considering the difference a few mm can make.

jeffy
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Joined: Sun Oct 05, 2014 11:51 pm

by jeffy

Also, what do you mean by "safely use Dura Ace" pedals?

Not sure I understand the dangers of Dura Ace.

Citizenfox
Posts: 197
Joined: Fri Apr 03, 2015 1:22 pm

by Citizenfox

jeffy wrote:Also, what do you mean by "safely use Dura Ace" pedals?

Not sure I understand the dangers of Dura Ace.


Not needing virtually unlimited float.

DanW
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by DanW

We used an MRI model


Interested who this was with (general group/ organisation even). Great attention to detail in your fit- I like their style :thumbup:

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Calnago
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by Calnago

What is an MRI "model"? I know of course what an MRI is and have had a few but I've never heard the term "model" used. I presume an MRI was in fact taken to produce this model?
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DanW
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by DanW

When I say "MRI model" I am talking about going through the MRI scan performed on a participant slice by slice, identifying voxels which belong to a certain tissue and putting together all of the slices to create a 3D CAD model of the tissue layer by layer. I have a nice SLS model of my knee at home :D

Measuring distances between landmarks on an MRI image is more likely what happened... If KW got the full 3D CAD model level of info towards a bike fit then I'd be massively impressed and want one of those fits! :beerchug:

by Weenie


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Calnago
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by Calnago

I thought @Kwalker was the one who said they used an MRI model for his fit. Sorry if I got that mixed up. I'm on Tapatalk and when things are quoted it seems to leave out the names of who said it when quotes from different people start getting nested. I get what you mean by the "model" and that's kind of what I assumed. I just thought there's no way a bike fitter would 1) do a complete MRI then 2) create a 3d CAD model from it to do a bike fit. I've had an MRI done on my lower back (L5/S1) due to a herniated disc about 15 years ago, and the images were astounding. But unless you already have an MRI scan at the ready I just can't imagine a bike fitter sending you for one. They are not cheap for one thing, like over $1000 for sure, and most likely used to determine the landmarks and distances from a single image from the entire scan rather then piecing together a full 3D CAD "model" as you are talking about. I'm sure it could be done at a significant cost, but I've never heard of it actually being performed for the purpose of a bike fit.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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