Ski Skating Kinematic Comparisons across Technique and Speed
Optimal ski skating performance demands an interplay of techniques and requires technique choices which best fit terrain and conditions. V1 is a commonly used uphill skating technique with one poling action of the arms for the two skating strokes of a cycle whereas V2 technique involves a poling action with each skating stroke. A cross-over point of relative effectiveness for V1 and V2 techniques has been identified at about 5° with V1 more effective on steeper slopes. Kinematic differences of V1 and V2 likely influence the physiological demands of the techniques. PURPOSE: To determine skier kinematic characteristics of V1 and V2 skating on a 5° uphill slope through a range of speeds. METHODS: Ski skating was analyzed while treadmill rollerskiing at 3 individualized speeds ranging from moderate (2.5 ? 0.2 m/s) to race speed (3.4 ? 0.3 m/s) using V1 and V2 techniques in separate sessions all on a 5 degree slope. Markers on skis, poles and body landmarks were tracked at 240 Hz using a Qualisys ProReflex system. Six cycles for each condition were analyzed using temporal and ski and pole positioning characteristics. Eight elite skiers from cross-country and nordic combined national teams participated. RESULTS: For both V1 and V2 skating, as speed increased by about 36%, cycle frequency and cycle length increased by 11 and 22% respectively. Ski and pole phase times systematically decreased with speed while phase percents of full cycle were nearly constant. Ski glide times for V2 are about 30% greater than for V1 while poling times for V2 are less than 70% of V1 poling times. Ski angles for V1 skating are wider than for V2: about 19 vs. 14 degrees. While pole positioning for V2 is similar on each side with an orientation of about 6-8 degrees from forward, V1 pole positioning is asymmetrical. Neither ski nor pole positioning changed with speed. CONCLUSIONS: Both cycle frequency and cycle length changes are used by skiers to increase ski skating speed for V1 and V2 techniques. However the proportions of a cycle remain nearly constant across speed as do ski and pole positionings. In V2 skating the poling frequency is double the cycle frequency. On uphill slopes such as this study, V2 poling frequency at high speed (about 1.2 Hz) may be a limiting factor for steeper slopes or further speed increases as this may limit effective poling force generation.
Publisert i ?, 2006
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