Analiza kolenskih vezi pri uporabi smuči različnih širin in s tem povezani dejavniki tveganja za poškodbo

Sodobne alpske smuči postajajo v zadnjih letih vse širše, saj naj bi bile ob manjšem naporu bolj vodljive. Najnovejše meritve pri smučarjih pa kažejo na to, da lahko pride pri širših smučeh zaradi smeri delovanja sil v zavojih do večje obremenitve kolena na zunanji nogi in s tem do tveganja za poškodbo kolenskih vezi.

Naslov prispevka: Analysis of knee joint movement when using alpine skis of different widths and the related risk factors for injury
Avtor: Martin Zorko
Vrsta predstavitve: Ustna predstavitev
Strokovno srečanje:  4th International Scientific Students Conference on Kinanthropology
Kraj in čas srečanja: Olomouc (Češka), 17.-19. april 2013

Povzetek:

Background: 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 or skiing in a straight line. With this point of application, the torques that affect 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.

Objective: To establish differences in positions of the knee joint of competitive skiers during a ski turn using skis of different widths.

Methods: Three study subjects performed two runs using skis with the width under the boot of 8 and 12 cm. Both skis had the same declared side cut. Each run included ten equal giant slalom turns. The skier wore an inertial motion capture suit (Xsens MVN BIOMECH) 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) Leica Geosystems, series 1200.Based on the combined data from the RTK GNSS receiver and the inertial suit, four standard phases of the turn were defined. 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 Fujifilm HS 10 high-frequency video camera. A Kolmogorov-Smirnov test was applied for the statistical analysis and the results at p<0.05 were adopted as statistically significant.

Results: In terms of all skiers’ average turns on the outer ski, knee flexion was significantly larger when wider skis were used. Knee abduction was significantly smaller with wider skis and was constantly around 0. Internal rotation on the narrower skis in the second part of the turn was statistically significantly higher than the internal rotation on the wider skis. There were no statistically significant differences in the first part of the turn. Only for rotation it was statistically significantly larger on narrow skis in the case of every skier, whereas in terms of flexion and abduction the results of individual skiers were less consistent. All three skiers reported a subjective feeling of poor balance on the wider skis and a reduced ability to direct them.

Conclusion: The larger knee flexion on wider skis could mean an attempt to lower the body’s centre of gravity due to some difficulties with keeping balance. The smaller abduction and smaller rotation on the wider skis mean lower tension on the medial collateral ligament and perhaps a higher loading on the inner knee compartment. To more accurately define the risk factors for injury, the forces that act on the knee joint would have to be measured.

Key words: alpine skiing, injury prevention, inertial sensor, kinematics, knee