INTRODUCTION: In World Cup competitive alpine skiing, the risk of injury is relatively high compared to other Olympic winter sports [1]. While injuries in giant slalom (GS) were found to be primarily linked to the mechanics of turning (i.e. high turn speeds, small turn radii, large ground reaction forces and high impulse), injuries in downhill and super-G were more associated with speed and impacts [2]. Expert stakeholders see course-setting as the primary measure to reduce injury risk [3]. Biomechanical research has shown that course-setting manipulations are suitable to reduce injury risk factors such as speed, forces, turn radii, inward lean, etc. [4,5]. However, these effects were only found in experimental settings in steep terrain and for a few turns [4] or in a competition setting with one forerunner only. Therefore, this study assesses the effect of a series of gates with increased offset on skier mechanics in flat terrain. METHODS: 5 male and 2 female World Cup skiers, members of the Norwegian alpine ski team, participated in the study. An open rhythmic course was set on a slope with an average incline of 13 degrees with an average gate distance of 27.0m and a 6.6m offset. Athletes skied first in that original course (course 1) before the gate offset was increased by 1.0m (course 2) and later by 1.5m (course 3). Athletes skied three runs in each of the courses. Terrain and course set were measured using static differential GNSS. Athletes carried a differential GNSS from which speed, ground reaction force, turn radius and impulse (the integration of ground reaction force over time) were calculated. Athletes also subjectively assessed the consequences of the course set changes. RESULTS/DISCUSSION: In courses 2 and 3, where offset was increased by 1.0m, resp 1.5m compared to the original course (course 1) speed was reduced. Each additional gate with increased offset lead to an additional reduction in speed. Course 2, where offset was increased by 1.0m, caused a speed reduction per turn of about 0.7km/h compared to course 1. In course 3 where the offset was increased by about 1.5m speed reduction per turn was about 1.0 km/h for both sexes. Increased gate offset in the flat terrain did not lead to any increase in maximal ground reaction force or decrease in minimal turn radii, while the impulse and the subjectively perceived physical load on the athletes were increased with increasing gate offset. The course set intervention had similar effects on women. CONCLUSION: In flat terrain, the main consequences of increased gate offset are speed reduction and an increased physical load, while minimal turn radius and maximal ground reaction force were not changed. Course setters should consider the trade-off between speed control and physical fatigue when setting courses in flat terrain.
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