Impact behaviour of ski-boots against different obstacles

Impact events during skiing are frequents and can lead to damages on the equipment or injuries to the skiers. In particular, the ski-boot can be subjected to impacts either during skiing or during falling. Furthermore, kicking actions are frequent in the resorts after skiing and may involve high impacts energy. Aims of the work were: i) to evaluate impact loads acting on the boots worn by a skier during voluntary kicks against obstacles of different shapes; ii) to estimate the energies involved in the impacts for comparison with experimental impact tests on boots using a drop tower. Kinematic data were recorded by means of a stereophotogrammetric system (BTS-Italy) composed by 6 cameras working at 120 Hz. A 50 kN Futek load cell and 2 uni axial accelerometers fixed under the boot sole for vertical and horizontal acceleration were connected to an IMC Cronos data acquisition system to collect kinetic data at the obstacles with 50 kHz sampling rate. The tester was asked to perform 4 types of kick (toe kick, shell kick, heel kick and instep kick) against three types of obstacles (flat, round and prismatic) with the boot at room temperature. A session with the ski boot at −20° was also performed. A 2D lower limb rigid model was developed to estimate impact energy absorbed by the boot. The peak values of impact loads were measured with different types of obstacle or kicks directions and the highest speed value of 8.8 m/s during toe kicks was recorded. High value impact energies were estimated from the limb total energy loss during impact: the maximal value was of 128,3 J.