3D motion capture technology gives Olympic triathletes the perfect fit

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Retul active motion capture technology

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April 18, 2008 The Retul 3-D motion capture and analysis technology system for cyclists promises fast and accurate data collection to aid in bike fitting, avoiding injury and ultimately, better bike design. The active system, which uses infra-red LEDs (light emitting diodes) placed on the body in specific skeletal locations will be used by the US Triathlon team in the lead up to the Beijing Olympics.

Designed specifically to attach to bikes and collect data specified by the users, the technology determines everything from saddle and handlebar positions, to the position of their feet on the pedals and their wind resistance, giving coaches instant and valuable data to optimize bike fitting, helping to avoid injury during training as well as squeeze out better racing times.

Prior to using the Retül software, all riders are interviewed and their own “fit” data is stored in client specific files, which can be accessed at any time to compare previous fittings with new data. This “active” system differs from passive systems (similar to those used for motion capture for films and video games) in that the tripod mounted LED sensor is tracking the light directly from the source (the LED diodes). This avoids problems of false data encountered by passive systems that use reflective markers which can be confused by additional reflective objects outside the system such as shoes, clothes, or the bike itself.

The system flashes an LED every 2.1 milliseconds (476 times per second) and takes a full set of body measurements every 34 milliseconds, making 29 full sets of body data per second. The sample sizes last anywhere from 5 seconds to 5 minutes, depending on the requirements of the rider. The software then processes all of that data in seconds, synchronizing the eight data points tracking them across longitudinal, vertical and horizontal planes. The fitter then analyzes the data from the sample and evaluates the need for position change. Once the changes are made, the process is repeated to verify effectiveness. This new data then becomes part of the final report, in addition to post-fit bike and equipment measurements.

Compact and portable, the whole system fits into a rugged case just 45" x 16" x 6" in size. and can be used to fit the same user for other types of bikes including mountain and cross.

Retül’s involvement with the US Triathlon team team began in February when expert fitter Todd Carver visited the Triathlon offices at the Olympic Training Center in Colorado Springs to provide the first few bike fits for a few of the Olympic hopefuls, including Andy Potts, Hunter Kemper and Sarah Haskins. The coaches and staff decided the portable technology was needed by the program for both training and races. The technology is also being used by the US Team competing in this year's Tour de France.

Beyond applications for elite athletes, Retül’s creators believe the common dynamic fit language will ultimately be used to further the science of fitting a bicycle to the human body and therefore help manufacturers make better bikes.

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