Ski skating force comparisons across technique and speed
Ski skating propulsion involves reaction forces from skis and poles. 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. At the cross-over point, similar kinetic characteristics are likely as both techniques are commonly used on such terrain. PURPOSE: To determine ski and pole forces and other kinetic characteristics in V1 and V2 skating on a 5° uphill slope. METHODS: Instrumented rollerskis and poles were used to measure reaction forces during V1 and V2 skating on a large treadmill. Force data were telemetered to a computer for recording. Subsequent analysis involved filtering and determination of impulse, peak and average force for each pole and ski, plus cycle characteristics. Five elite level skiers skated on a fixed slope (5°) with 3 individualized speeds ranging from moderate (2.5 ? 0.2 m/s) to race speed (3.5 ? 0.2 m/s) using V1 and V2 techniques in separate sessions. RESULTS: V1 skating involved greater cycle frequency (0.6 vs 0.8 Hz at race speed) and therefore reduced cycle length compared to V2 at each speed. Both cycle frequency and length increased with speed. While cycle time for V2 was greater than for V1, as a proportion, both techniques involved poling in 45 to 50% of a cycle and skating on each side 60 to 65% of a cycle. Peak poling forces and impulses were similar in both techniques, but average poling forces over a cycle were greater in V1 skating. While both peak and average ski forces were greater in V1 than in V2 skating, ski impulses were similar. CONCLUSIONS: V1 and V2 rollerski skating on a 5° uphill slope involves differences in frequency and in some force characteristics. While V1 requires greater cycle frequency, V2 skating with two double poling motions per cycle demands greater upper body frequency. Despite two poling motions, V2 poling impulse per cycle is similar in magnitude to V1 poling impulse. Similarity of kinetic characteristics helps explain the common usage of both V1 and V2 skating on moderate uphill slopes. Whether substantial kinetic differences are required on steeper slopes will be explored in subsequent research.
Publisert i Annual Conference of the American College of Sports Medicine, 2005
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