Ski Jumping: Altus, Fortus, Captus

First there is the in-run, when the squatting athlete glides on the take-off ramp. Then the impulse, these tenths of a second so crucial before the flight, with the body leaning forward, heels lifted, and skis almost in a “V”. During a ski jump, the athlete has to perform a complex movement at a speed of over 90 km/h for a very short time. Take-off is therefore the crucial phase.

“Coaches use conventional cameras to film the ski jumpers, but they don’t have any data on the parameters of the jump itself.” To complete his research, Julien Chardonnens, a doctoral student at the Laboratory of Movement Analysis and Measurement (LMAM), takes in a way the place of the ski jumper, who must both optimize the power which propels him upwards, and adopt a position which projects him forward. In order to understand and analyze how someone like Simon Ammann or Andreas Küttel approaches the different phases of a jump, the researchers at LMAM have fitted their own and 35 other athletes’ jumpsuits with sensors, which memorize the jump data. Thanks to the built-in accelerometers and gyroscopes, the sensors work like a miniature laboratory.

A useful training tool

Such measurements, coupled with a close cooperation with the coaches, enabled Julien Chardonnens to demonstrate statistically that the parameters used make it possible to analyze and to explain the quality of a jump. “We measure the jumper’s movement from take-off to landing. Thus, thanks to a biomechanical model and signal processing tools, we automatically extract parameters such as timing, dynamics, angular parameters, and inter-segment coordination.” In time, this research will help to develop tools which can be used to improve the training of junior athletes then, subsequently, to examine and optimize the champions’ performances.

Preventing accidents during competitions

After his research on the performance of ski jumpers, Julien Chardonnens is currently working on the prevention of accidents in competitive downhill skiing.

Commissioned by the International Ski Federation (FIS), the EPFL laboratory worked in association with the Institute for Snow and Avalanche Research, (SLF Davos) and the universities of Salzburg and Oslo to perform measurements during the World Cup in order to better understand how factors such as equipment, snow, and the position of pickets influence the risk of accidents:“This season, we are taking measurements on the openers and athletes on the World Cup circuit. We were present at five Giant Slaloms and five downhill, including Wengen and Kitzbühel.” There too, skiers are fitted with different measurement systems such as inertia sensors and GPS. But other parameters are also analyzed, such as snow conditions and equipment.

Research often begins with a question

For these scientists, who have a passion for translational biomechanics (the transfer of biomedical research to practical applications), research often begins with a specific question. In the case of ski jumping, it was Dr. Gérald Gremion, a specialist in sports injuries at the CHUV, who came up with the idea of a measurement tool. Professor Kamiar Aminian, LMAM director, is particularly keen on this close cooperation between the engineer and the coach or the doctor: “Not only does this give direction to the project, but it also enables us to get access to athletes and to validate our research.” A partnership which increases as years go by: more particularly, the LMAM has a laboratory of movement analysis within the CHUV, equipped with nine cameras which enable the dissection of the movement, prior to rebuilding it in 3D.