Technical Q&A with Lennard Zinn – Winter work

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By Lennard Zinn

For a little pre-Christmas change of pace, I thought I’d share with you some new technology I’ve been using in a different context that I think could be a great tool for studying efficiency of movement in cycling and triathlon. From December 6-10, I was at Tamarack, a beautiful ski resort near McCall, Idaho for a technique-intensive masters cross-country ski retreat. Three-time Olympian and eight-time masters world champion Jon Engen, a Norwegian transplant to Sun Valley, Idaho, led the camp. JoAnn Hanowski, who has won more ski marathons than any other American, and Jim Fredericks, former director of the Rossignol Nordic ski team assisted with coaching.

Engen’s knowledge of the sport is encyclopedic, his eye for technique is eagle sharp, and he is able to explain technique and design illustrative drills in ways that directly and immediately impact a student’s skiing. But it was the computer technology that Fredericks brought to the table that increased Engen’s impact many times over and that I think could have far-reaching consequences in cycling, swimming and running, among other sports.

Using a powerful and pricey video software package called Dartfish (www.dartfish.com), Fredericks converts films he shoots of students into three different formats to drive home ski technique tips to them. Engen and Fredericks have developed a teaching method using Dartfish computerized imaging tools called Athletic Imaging System (AIM).

With the “SimulCam” tool, video of one athlete can by overlaid over that of another athlete. The ghostly images moving back and forth literally through each other as they ski the same section of trail reveal details of force generation, ski placement, and timing that would be otherwise difficult to pick out, even in slow motion video.

Using “Split Screen” analysis of side-by-side images of two skiers traversing the same section of trail, the student can see clearly subtle differences in stroke length and body position.

Using “Stromation,” Fredericks spreads out multiple still images from a video series of a skiing section onto a single screen. This allows easy examination of body position and ski placement throughout a number of ski strokes.

These three methods of direct feedback to the student make it easy to see where to make corrections, and all three could be as useful for analyzing running and swimming technique as they are for analyzing ski technique. But a fourth Dartfish tool for studying moving angles in space would be particularly powerful in analyzing cycling positioning and pedaling technique.

In freeze frame, you can draw line segments on the athlete’s limbs in the video, and as the athlete then moves in slow motion or at full speed, the line segments move with them. The computer automatically determines the angles of intersection of the segments and displays them in large format on the screen. Allowing the video to proceed in slow motion, you can see how the joint angles vary throughout the motion. There is no fooling oneself here about body position; it is so exact that there can be no doubt of the angles your joints are moving through. Can you imagine being able to examine seat height by looking at the knee angles and ankle angles of a rider pedaling in slow motion? How about being able to explore the angle at the hip joint between the thigh and the torso? What a great way to discover how much a low, aerodynamic position can constrict that angle and tighten the hamstrings and low back and restrict breathing. Overlay it over a world champion time trialist, and you can see how much your angles vary from theirs, or how much more easily they can tolerate body angles that are painful to you.

The masters’ XC ski retreat in December at Tamarack was the first AIM camp and included great food, upscale lodging, great snow on great trails, not to mention fantastic coaching with cutting-edge video analysis tools. Rossignol, VOMax Clothing, Toko, and Vasa Trainer made the retreat possible. It included a DVD for each participant to keep of their own skiing video sequences with the Dartfish tools overlaid on them and Engen’s voiceover providing technique tips and suggesting corrective drills. For more information on future AIM clinics, contact Jon.Engen@olympian.org or frederij@pshift.com. Fortunately, Fredericks and Engen are both cyclists, and I have high hopes for doing some future work with cycling with them and their AIM technology.

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