Analiza gibanja kolenskih vezi pri uporabi alpskih smuči različne širine in s tem povezani dejavniki tveganja za poškodbo
Naslov prispevka: Analysis of knee joint movement when using alpine skis of different widths and the related risk factors for injury
Avtor: Martin ZorkoVrsta predstavitve: Ustna predstavitev
Strokovno srečanje: 6th International Congress on Science and Skiing
Kraj in čas srečanja: St Christoph (Avstrija), 14.-19. december 2013
Povzetek:
Introduction: In a ski turn, the point of application of the ground reaction force to the loaded/external leg is located where the inner ski edge contacts the snow and not under the foot as is the case when standing and skiing in a straight line. With this point of application, the torques that affects the knee joint may potentially change and – due to the skier´s compensation strategies – the positions and loadings on individual knee structures may also change. Such positions and distribution of forces in the knee joint may constitute additional risk factors for injuries and degeneration. The aim of the study was to establish differences in positions of the knee joint of competitive skiers during a ski turn using skis of different widths.
Method: Three study subjects performed two runs using skis with the width under the boot of 6.5 and 11 cm. Both skies had the same declared side cut. Each run included ten equal giant slalom turns. The skier wore an inertial motion capture (MVN BIOMECH, Xsens Technologies) which directly measured 3D accelerations, 3D angular velocities and 3D orientation at a sampling frequency of 120 Hz. The reference trajectory of the skier was measured using the Real Time Kinematics Global Navigation Satellite System (RTKGNSS; LeicaGeosystems, series1200). Four standard phases of the turn were defined: initiation, steering 1, steering 2 and completion phase (Mueller et al., 1998, Supej & Holmberg, 2010). The angles in the knee joint were measured in the sagittal, frontal and transversal planes. To facilitate the analysis, the skiers were recorded using a Casio Exilim Ex-F1 pro high-speed and high resolution camcorder.
Results: In terms of all skiers’ outer ski average the magnitude of knee flexion was not related to the ski width. Knee abduction was significantly smaller and relative external rotation was significantly larger using wider compared to narrower skis. All skiers reported a subjective feeling of poor balance on the wider skis and a reduced ability to direct them.
Discussion: By using the combination of knee abduction and external rotation on the narrower skis the skiers appeared to move the knee joint inward and towards the ground reaction force vector.The reason for that was probably the aim to reduce the knee joint varus torque. Using wider skies the knee joint remained in a more neutral position in transversal and frontal planes despite the possible higher varus torque. The reason for that could be the inability of the skiers to move the knee inward on the wider ski due to increased torques. As a consequence they had to use a different balancing strategy when using wider skis.
Conclusion: The results indicate a potential for a higher injury risk when using wider skis. Further studies incorporating dynamics are needed to elucidate the issue.
