Limited effect of load reduction by changing the ski characteristics on the anterior cruciate ligament in the slip-catch injury mechanism in alpine skiing.

In competitive alpine skiers, anterior cruciate ligament (ACL) injury is the most common and severe injury, and the slip-catch mechanism is one of the main injury mechanisms. Much effort has been made to prevent injuries by limiting the aggressive characteristics of the ski. However, there is no clear evidence on the effectiveness of equipment regulations for ski competitions aimed at reducing injury rates. Therefore, this study aimed to clarify the relationship between ski aggressiveness and load on the ACL in the slip-catch mechanism. Forward dynamic simulations were conducted incorporating the kinematics of the actual skiing motions measured in the experiment. The actual skiing motion was measured under four different conditions with inertial sensors, which differed in ski type, course settings, and skier's level. The ski parameters used in the simulation were obtained by measuring the skis used in the experiment. The snow and body inertia parameters were obtained from previous studies. The sensitivities of ski characteristics to the load on the knee joint and ACL were generally low. The only significant sensitivity to the ACL force was the tail length; however, the load reduction effect was small. It is important to recognize that there is a severe limitation to the prevention of ACL injuries by limiting the ski aggressiveness. The results of this study indicate that improving the skier's motion (avoiding the knee extended position, and making the pressure on the skis more forward) and tactics (not catching the snow surface) are more effective measures for preventing ACL injury.