Dynamics of Freestyle Skiing – Equipment development and implications for injury prevention strategies

Abstract

Alpine skiing is a popular recreational and competitive sport and is associated with a comparably high risk of knee injuries. Freestyle skiing, as a growing discipline in young people, requires diverse skills beyond those involved in traditional alpine skiing. Therefore, it is likely these disciplines produce different loading and accordingly, different injury patterns. Consequently, in order to develop a technology for the prevention of injury such as rupture of the anterior cruciate ligament (ACL) strength and loading at the knee during skiing activity should be investigated. The current project is unique as it includes a comprehensive three dimensional (3D) analysis of movement and dynamics in the area of mogul skiing. Three consecutive studies are presented, each of which are linked to the goal of providing insight into the biomechanical demands mogul skiers are exposed to during performance. The first study evaluated the effect of a new force transducer on skiing kinematics. This study revealed no major impairments of mogul skiing technique and thus set the foundations for study II and III. These studies were designed to quantify the influence of ski boot modifications towards a greater anterior ankle flexibility on kinetic and kinematic parameters in mogul skiing. A custom-built mobile force measurement device and a high speed camera system were used for data collection for all components of ground reaction forces (GRF) and 3D marker data in the field. The collected data were used as input values for a modified computer model utilised for the estimation of joint kinematics and net forces and moments in the knee. Prior to the commencement of the intervention studies several tests of precision and validity for the measurement tools were conducted. High peak net forces and moments were calculated for the knee during mogul skiing, however, no critical average values for knee joint loading were revealed. The ski boot modification altered the body posture and reduced knee joint loading at maximum force. Hence, the new boot characteristics can potentially prevent injuries in mogul skiing. The current data base should be used as the basis for further in-depth freestyle skiing investigations to improve injury prevention strategies and thus reduce the high rate of knee injures. Secondly performance parameters can be reconsidered and presumably optimised using the current data as a starting point.