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20

June

Retul: 3D Motion Capture Bike Fitting

Your bike should fit you like a glove, and hopefully better than O.J.’s glove. The folks over at Retul have developed a system to make that a reality.

I was recently certified by Retul as a bike fitter. Does that mean I will be doing bike fits? Well, no, but I might be helping out once in a while at the new Rev3 Triathlon retail store opening in Manassas sometime next year. This newsletter outlines a tool that they are already using over there to get cyclists and triathletes properly fit on their bikes and the Retul system is nothing short of amazing…

Analogy alert!…We know from many studies (see here) that looking at the non-moving foot is a terrible way to figure out what kind of shoe you should wear. This is because of the simple fact that the shape, flexibility and control of the foot is much different when you are running than when standing or laying on a table. Those that have high arches may not when they run. Those that seem to be flat footed when standing may control their foot very well when they run. You just don’t know until you examine the moving foot.

Getting the proper fit on a bike is no different. Measuring the body in a static position does not represent what will be happening when you are actually pedaling. For example, do you have poor hip mobility that will cause you to rock back and forth? Do you point your toes down once you start pedaling? Do your knees track toward or away from the top tube when trying to get some power? If the fitter moves the saddle back a centimeter, how do you react to that in your knees, hips and ankles? These are all questions that you cannot know from a static measurement.

Enter the Retul Bike fit. Retul uses a 3D motion capture system that provides real time kinematic data showing knee drift to and away from midline, joint angles at the top and bottom of the pedal stroke for the hip, knee, ankle, shoulder, elbow etc. and it is all done on a bike that can be adjusted on the fly. In other words, we can move the saddle up, down, back and forth and the handlebars up, down, back and forth while you are pedaling so there is instant feedback for how the changes affect how you feel on your bike. Not only how you feel, but how your body reacts to the changes because the system is measuring 3D data of you pedaling with down to millimeter precision. This eliminates the guesswork.

For example, we recently had a triathlete who’s knees were too bent at the bottom of the pedal stroke. By raising the saddle a bit, you would expect the knee angle to open up at the bottom of the pedal stroke. Is that what happened? Nope, the knee angle stayed the same, because he compensated by increasing the toe down position of the ankle. We would never have known that without the Retul system.

Video of the Retul System in Action:



I have had three different bike fits in the past five years. Two of them were done in the standard fashion: You get on the bike, pedal for a bit, the bike fitter uses a goniometer and a plumb bob to get some measurements and then asks you to get off the saddle so he can move the bike saddle and handlebars around a bit. He then rechecks the goniometer and plumb bob and then asks you to pedal again.

Bike Fitter: “How does it feel now compared to before?
Me: “Ummmm…Good, I guess…I don’t know, can you move it back to the way it was so I can feel the other way again?
Bike Fitter: “I hate you

After these exchanges, he is satisfied that he measured properly and you’re on your way. Contrast that with the Retul system where there is no guesswork for the bike fitter (via the data) or for the cyclist (via the instant feel for the bike change).

After the Retul bike is configured to the way both the fitter and the cyclist are happy, the bike is “Zinned”. The fitter takes a “magic wand” and maps out the 3D data points of the bike so the bike fitter can precisely save your fit electronically and then creates a report telling them how to exactly replicate that fit onto your bike or any other bike. Again, the guesswork is eliminated.

Just take that report to any bike dealer, ask them if the fit can be replicated on the bikes that they sell. If it works, test ride that bike with your exact fit to make sure that you are happy with the bike. Now you can go into any bike store without fear and know you are getting the right bike for you.

If you are interested in getting a bike fit over at the Rev3 Triathlon retail store via email: bikefit@rev3tri.com

- Kevin Maggs, ,

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