In contrast to the drop in the incidence of fractures of the lower leg that has been observed in recent years, the incidence of knee injuries has not decreased in skiing. There has even been a relative increase of severe knee lesions and isolated ACL ruptures, prompting us to conduct a comprehensive study of this phenomena.
The goal of the study was to develop a new measuring device for alpine skiing research by combining motion analysis, pressure and force measurement, comprehensive examine the forward/backward movement in ski boots in the lab and by means of telemetry on the slope and to come up with a proposal for a new safety concept to reduce the high number of knee injuries in alpine skiing in the future.
The first study was devoted to the forward movement in ski boots. Studying nine beginners and eight experts we found a 20% (sign. 0.05) lower forward lean capability of the beginner group in the same boot.
A randomized study with cross over design conducted on the slope, where we equipped 16 skiers with either soft or stiff boots for the duration of five ski days, revealed the learning behavior and forward position on the slope depending on the boot. The pupils became definitely less adept at learning if they were required to wear stiff ski boots and showed a significant lower forward flex angle. A skiing style in backward lean position was adopted and supported by the fixed backward spoiler.
In order to quantify the influence of the backward spoiler a special ski boot was constructed allowing the rear spoiler to give way at a variable, defined stiffness and register the angular displacement and horizontal force Fh. The results on ten male subjects showed most clearly that even a medium rear spoiler resistance will significantly reduce the peak force values by a factor of 5.5. The deceleration at the knee joint level is significantly higher (factor 1.6) in case of a rigid spoiler. The lab tests could be confirmed on the slope (significant reduction of max. force by factor 8). It also proved that normal skiing can be performed in such a boot without limitations.
In consideration of our results it is concluded that the principle of safety bindings must definitely apply in future in equal measure also to the ski boot. As a proposal for future safety concepts, we developed a safety ski boot, that allowed for the first time the rear part to open and give way after a certain amount of force (adjustable preload). The backward release bindings, which can often produce dangerous malfunctions if a strong force acts on them for a short while, and which were therefore only very reluctantly if all accepted by skiers, could thus be complemented by a safety system in the boots.
In all probability this would be a contributing factor to reducing the high incidence of knee injuries in skiing.