SAFETY ASSESSMENT OF JUMPS IN SKI RACING Nachbauer, W. 1, Mössner, M. 2 and Schindelwig, K. 1 1) Department of Sport Science, University of Innsbruck, Austria 2) Centre of Technology of Ski- and Alpine Sport

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Introduction Statistic world cup ski racing From 1605 athletes of the Austrian Ski Federation winter seasons of 1995/96 to 2012/ injuries - from these 237 severe (Nachbauer et al., 2013 ) Landing back-weighted after jumps second most common skiing situation of an ACL injury (Nachbauer et al., 2013) Accurate prediction only with wind tunnel experiments (drawback - high costs) (Brownlie et al., 2010, Chowdhury et al., 2010)

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Goal Develop a simulation model to predict the injury hazard of jumps in downhill ski races Hazard measure - equivalent fall height (EFH) Variable inclination landing area – concept of effective landing height (ELH)

Method: field measurement 18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June jumps – 145 jumps analysed Sprung ins Himmelreich (SH), Panorama Sprung (PS), Mausefalle (MF), Kamelbuckel (KB) 3 Cameras 20 Hz, 6 MP (Casio Exilim EX_F1) 300 HZ, 0.2 MP (Casio Exilim EX_F1) Theodolite (CTS-2B) position of cameras, gates, … Inclinometer (Pieps 30° Plus) slope inclination

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: 3d reconstruction

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: 3d reconstruction skier’s plane π ε image coordinates

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: simulation model

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: simulation model Integration of the equation of motion Runge-Kutta scheme Δt of 0.01 s Drag and Lift determined by parameter identification Least squares fit the solution of the equation of motion is fitted to the measured trajectory

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: simulation model t1t1 t2t2 v2v2 v1v1 v1v1 v2v2 v 2-1

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Results: reconstruction accuracy rms deviation for the ski lenght: 2.2 cm max. difference between cameras: 11.8 cm for center of mass Eq

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Results: high speed video of landing movement

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Method: jump parameter Jumpv 0 (km/h)α 0 - β 0 (°)D (m 2 )L (m 2 )EFH (m) SH 86 (77-91) 2.3 ( ) 0.32 ( ) 0.06 ( ) 0.78 ( ) PS 92 (85-99) 0.1 ( ) 0.43 ( ) 0.07 ( ) 0.62 ( ) MF 93 (86-97) 2.1 ( ) 0.46 ( ) 0.02 ( ) 0.89 ( ) KB 109 ( ) -0.1 ( ) 0.42 ( ) 0.01 ( ) 1.98 ( ) α 0 - β

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Results: EFH take-off angle – approach speed jump „Mausefalle“

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Results: EFH versus ELH jump „Kamelbuckel“ EFH (m) ELH (m)

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Diskussion: summary Accurracy greatest difference of vertikal position: 118 mm  error of determination of drag and lift area +/- 0.3 m² EFH versus ELH equivalent fall height (EFH) assess the energy absorbed upon landing, if inclination of landing area is constant equivalent landing height (ELH) is needed, if inclination of landing area is NOT constant Simulation model a prediction of the injury hazard of a jump is possible

18 th annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE, 26 th – 29 th June Conclusion Simulation model was developed to predict the equivalent fall height for jumps Necessary parameters were measured for four jumps during world cup races. Take-off angle, velocity and steepness of landing area are the most dominant factors for the equivalent fall height. The equivalent fall height is an important measure to assess the effect of possible impact hazards and, thus, the given simulation model can be used to improve the safety for jumps in ski racing.