Is Retul 3D Motion Capture worth it for bike fitting?

Discuss light weight issues concerning road bikes & parts.
vinuneuro
Posts: 103
Joined: Mon Mar 06, 2017 10:34 pm
Location: Chicago

by vinuneuro

I understand the the fitter's skill and experience are the number one factors in getting a good fit and the one I am considering is highly rated and experienced. Standard fit with this shop is $250 and $350 with Retul Motion Capture. Is it worth the extra $100 to do the fit with the Retul digital motion capture?
'16 Spec Diverge Expert

by Weenie


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oldnslow2
Posts: 222
Joined: Wed Feb 03, 2016 1:50 pm

by oldnslow2

first, any fit should include a refit a few months later.

Also and fit is a "perfect world" approximation. Within a few month of a fit, i changed my stem and cleat position. I was much more comfortable.

DJT21
Posts: 223
Joined: Sun Mar 27, 2011 7:35 pm

by DJT21

vinuneuro wrote:
Sun Mar 04, 2018 6:13 pm
I understand the the fitter's skill and experience are the number one factors in getting a good fit and the one I am considering is highly rated and experienced. Standard fit with this shop is $250 and $350 with Retul Motion Capture. Is it worth the extra $100 to do the fit with the Retul digital motion capture?
I'm not sure what the shop are saying by charging extra for the motion capture? Surely if their fits were good enough then you wouldn't need it?

As in, if you paid $250 and they set you up in a certain position. Then if you paid $350 for the motion capture and they set you up differently then surely that'd prove they're not very good fitters?

TBH, I don't know what motion capture is, I'm just presuming it's some sort of video that looks at your positino and pedal stroke.

TobinHatesYou
Posts: 1880
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Retul’s IR capture is good, but it’s just a tool. In the hands of an inexperienced or lazy fitter, it would be pretty useless. Your dynamic angles are going to depend on whether the fitter put the sensors on the right landmarks. It’s nice in that it can tabulate the data in real-time vs using overlays with video fits.

SuperDomestique
Posts: 92
Joined: Mon Sep 05, 2016 11:07 pm

by SuperDomestique

Bit of a strange one. Only thing that you could say justifies the extra is the output that you get as a client from retul although I don't feel that's worth much.

What if anything would be different with the assessment and fitting process aside from using retul to measure angles, that's the key question?

Myself, I want the result of a fitting to always be as good as possible so I only do one fitting service and that gives you everything I have: Video analysis, pedalling/power analysis, saddle pressure mapping and custom footbeds. I don't like retul, but that's just me. I did use it for a while and also bioracer 4d. Prefer video.

cyclenutnz
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by cyclenutnz

I would charge more to do a fit without 3D - having good data makes decision making so much easier.
Of course, I don't use retul because I created competing software but the point remains. A good fitter with good data will do a better job than a good fitter with inferior tools or a poor fitter with the flashest kit possible.
I'd suggest that a fitter that charges more for 3D mocap doesn't really understand the tool as they see it as a burden to have to set it up, rather than as a boost to their fitting service.
http://www.speedtheory.co.nz
http://www.velogicfit.com - 3D Motion Capture and Frame Finder Software

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wheelbuilder
Posts: 531
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

cyclenutnz wrote:
Mon Mar 05, 2018 2:55 am
I would charge more to do a fit without 3D - having good data makes decision making so much easier.
Of course, I don't use retul because I created competing software but the point remains. A good fitter with good data will do a better job than a good fitter with inferior tools or a poor fitter with the flashest kit possible.
I'd suggest that a fitter that charges more for 3D mocap doesn't really understand the tool as they see it as a burden to have to set it up, rather than as a boost to their fitting service.
That is a well done website. Nice work.

TobinHatesYou
Posts: 1880
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Also it all goes out the window if the emitters, sensors, etc. are in the wrong place...and if the zin wand is used an an imprecise fashion.

cassard
Posts: 95
Joined: Wed Jan 24, 2018 12:31 am

by cassard

no it's not. To much flaws in the system. No repetability and useless tests in the assesment (some are even wrong).

You would be better with a 2 hour fit with a heatly/rehab professional that has knowledge and experience in both cycling and biomecanics

leandrofresh
Posts: 30
Joined: Mon Jul 13, 2015 12:45 am

by leandrofresh

No. Absolutely not. Do not pay more for that. It's just numbers on a screen. Choose a good fitter instead. And he won't even need lasers to tell that you are riding ok. Also. Do you have a power meter? It's easy to tell with a power meter that tells Torque and pedal smoothness if you position is perfect.

TobinHatesYou
Posts: 1880
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by TobinHatesYou

No, JFC, no.

Using torque effectiveness and pedaling smoothness to judge a fit is idiotic. Using tools like polar view (Rotor, Wattbike) or torque vectors (Pioneer) fall into the same category. You can be incredibly smooth while also mildly hyperextending your knees or pedaling toes-down. You can be smooth with a completely inappropriate saddle position.

Motion capture is fantastic for making sure a cyclist doesn't injure himself. Fine tuning within that range to achieve maximum power at no expense in comfort is the goal, not going from 25 to 27% pedaling smoothness.

leandrofresh
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Joined: Mon Jul 13, 2015 12:45 am

by leandrofresh

TobinHatesYou wrote:
Tue May 22, 2018 6:50 am
No, JFC, no.

Using torque effectiveness and pedaling smoothness to judge a fit is idiotic. Using tools like polar view (Rotor, Wattbike) or torque vectors (Pioneer) fall into the same category. You can be incredibly smooth while also mildly hyperextending your knees or pedaling toes-down. You can be smooth with a completely inappropriate saddle position.

Motion capture is fantastic for making sure a cyclist doesn't injure himself. Fine tuning within that range to achieve maximum power at no expense in comfort is the goal, not going from 25 to 27% pedaling smoothness.
You shoud tell Shimano that you think is idiotic. Maybe one of the most powerful tools in bikefitting like Shimano dynamic fitting is totally wrong and they didn't notice until you tell them that torque and smoothness are totally useless. And It's just another tool to validate a correct position, not the only tool.

If you are in a wrong position pedal efficiency certainly drops. But If your position is improved you certainly will notice with more watts. Sometimes pain it's and indicator of wrong pedalling technique, not incorrect position, so imho is a very powerful tool. But not judgind those metrics alone. Son don't twist my words.

Knee hyperextension can be judged by a good fitter eyes and tools way simpler than the 3D motion capture. But it's unlikely that you can tell that the cyclist isn't pedaling right judging with a 3d motion capture. Bikefits nowadays is all about to reeducate the cyclist, not just to look for angles in a screen, that you can do it without 3d system. If you have a bad technique but a correct position you will experience discomfort. If you have the right angles validated with the retül but the rider has a bad pedal stroke and he pushes down too much, his knee will extend outside range and may experience pain in the hamstrings or lets say the adductors.

So, yes. 3d systems worth nothing with a good fitter behind. And yes, if watts and smoothness are on the rise after bike fit and there's no pain you are on the right path. And also yes, not every power meter on the market is to be trusted, but you can judge things using them even if they are not accurate but as long they are consistent. If they overestimate by a 5% but it does every time you ride your bike the information will be useful.

And so you know, when you do a bikefit you look to correct excessive toe-pedaling or heel drop, knee extension and alignment, cause you know what? They improve efficiency. And efficiency is better torque, smoothness and watts. There's a reason to have a certain knee angle and it's cause it's a balance between efficiency and keep joints and muscles working in a safe bracket. You may be able to ride in a higher saddle height if you are pushing with the correct technique. And If I don't tell you how you should be pedaling and see knee overextension in the 3d I will have to lower the saddle to keep you in the safe and efficient zone. So yes, number in a screen are just that, but a good bike fitter is everything.

Any chance you are a bikefitter so you can sustain such a bold claim?

Sorry but english is not my main language, so I hope I made myself clear. And you can disagree, but no need to be rude. I can see that you do that very often.

TobinHatesYou
Posts: 1880
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by TobinHatesYou

Motion capture is way better than using your eyes/brain because it records way more data. Your eyes might miss a single pedal stroke where the knee hyperextended due to rocking or less ankling, but a data recording device will not. If you scroll up, I already said a toolset is only as good as the fitter who uses them

However this does not extend to extrapolated numbers like torque effectiveness and pedaling smoothness. I don’t care what Shimano, Wattbike, Rotor or Pioneer claim about smooth pedaling. There is no correlation between comfort or power increasing while pedaling at 60% pedaling efficiency with a Pioneer crank vs 30%. In order to improve those numbers you effectively need a perfectly round pedals stroke with a constantly changing torque vector, and you also need to use your calves/hamstrings inordinately more. Also a number like Pioneer’s pedaling efficiency is based off an entirely different formula than say, Cycling Dynamics pedaling smoothness even though they hint at the same thing. We simply do not have enough of a grasp of the biomechanics involved to make these judgments.

leandrofresh
Posts: 30
Joined: Mon Jul 13, 2015 12:45 am

by leandrofresh

TobinHatesYou wrote:
Tue May 22, 2018 7:43 pm
Motion capture is way better than using your eyes/brain because it records way more data. Your eyes might miss a single pedal stroke where the knee hyperextended due to rocking or less ankling, but a data recording device will not. If you scroll up, I already said a toolset is only as good as the fitter who uses them

However this does not extend to extrapolated numbers like torque effectiveness and pedaling smoothness. I don’t care what Shimano, Wattbike, Rotor or Pioneer claim about smooth pedaling. There is no correlation between comfort or power increasing while pedaling at 60% pedaling efficiency with a Pioneer crank vs 30%. In order to improve those numbers you effectively need a perfectly round pedals stroke with a constantly changing torque vector, and you also need to use your calves/hamstrings inordinately more. Also a number like Pioneer’s pedaling efficiency is based off an entirely different formula than say, Cycling Dynamics pedaling smoothness even though they hint at the same thing. We simply do not have enough of a grasp of the biomechanics involved to make these judgments.
Yes and no. Motion capture and specially retul 3d system has a lot of flaws and the data you can see in the screen sometimes is not even close to accurate. So I wouldn't ever rely on what I see on the screen alone to judge knee hyperextension, the sensors tend to move a lot during the recording. But if you talk about not missing a single detail during the stroke It's enough to use a high speed camera recording with 100fps instead of using the 3d system. Much more reliable. The Retül 3d is just and expensive toy.

Actually there is correlation between comfort and power increasing. Discomfort is caused by a wrong position that leads you to work with your muscles and joints out of range and lets say an excessive high saddle or too backwards, or tilted will stop you from pushing the pedals in the right vectors and with enough smoothnes. And that's bikefitting 101. For example if you have a too low saddle height you might be dropping the heel and having a bad KOPS (knee too far back from the pedal spindle that will lead you to pedal pushing forward (diagonal) like kicking the pedal to the front instead of down. If you are in the right position and you learn how to pedal with the right tecnique then yes. You will feel more confortable and become more efficient.

And again you are wrong. efficiency doesn't work like you say, the formula doesn't work just doing round pedalling technique and not even engaging every single muscle you have in your legs. For example, having the cleats far backwards as possible actually disengage the use of calves and gives you a smoother pedal stroke. There are two ways of achieving a high pedalling efficiency: You can achieve the same effectiveness pedaling with a round technique or with piston technique as long as you don't accumulate negative readings. That means doing a perfect pedal stroke around the entire circle, or when you pedaling in piston style by releasing completely the force in the negative zone of the pedal stroke. And that is with Shimano, Pioneer, Favero Assioma duo, Watteam Powerbeat, Stages, etc. A power meter doesn't work by just detecting the flex of the material, it also needs the vertical acceleration to be accurate. And that's torque and smoothness calculation to show the real wattage output. If you are in a wrong position or have a bad pedaling technique force vectors and vectorial acceleration will not be optimal and that will give you low reads of torque, smoothness and watts.
And what you call formulas are actually supported by lots of research and studies conducted to thousands of cyclists, pro, amateurs, and recreational. I can see very often that people don't really understand how these two metrics work. And I don't blame them, cause there's actually very little info about it.

I mean, If you can't trust every technology applied to bike fitting, I can't see why you trust so much the most unreliable tool on bike fitting world.

I'am currently studying bike fitting. So what I say is based in what I have been taught so far. But bikefitting science is constantly changing and nor me or the best bike fitter in the world can speak the ultimate truth so far... More research Is needed to be done.

RussellS
Posts: 789
Joined: Wed Feb 03, 2010 1:31 am

by RussellS

Concerning the Retul fitting system. My brother had the Retul fitting done recently. It produced odd results as far as I am concerned. He ended up being recommended a very small bike frame with very upright and short position. Short upright stem. It seemed to only look at his leg length only to determine frame size and completely ignored his torso length. He has short legs and long torso, so he really needs a frame with no standover at all and a long reach to the bars. I don't know if the Retul thing recommended this by itself, or the fitter entered various numbers to force the Retul to recommend this. So I'm not sure any official fitting system is worth anything. Its all up to the fitter. I can "fit" on a 50cm frame and a 64cm frame. Neither is the right size though.

by Weenie


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