INTRODUCTION: Regarding WC sprint races, a steady increase in skiing velocity in both techniques can be stated, This might be a result of an upcoming specialization of athletes on the sprint, and of technical modifications for the sprint. To date only Holmberg et al. (2005) have demonstrated a so-called "sprinter-like" double poling (DP) technique. Biomechanical data for the diagonal stride (DIAG) and skating technique is lacking. Stöggl et al. (2007) have shown that maximal skiing speed was highly related to sprint performance. Additionally it was suggested that faster skiers produced longer cycle lengths (CL) at lower cycle rates (CR) in maximal speed tests in DP and DIAG. The purpose was to get information on kinematic and physiological determinants of maximal skiing speed in the skating and classic technique. METHOD: 18 elite XC skiers performed three maximal anaerobic roller skiing tests (MART) on a treadmill (techniques: DP, DIAG, V2). The protocol included stages of 30sec with 100sec break in between. In DP and V2, treadmill speed was increased at 0,3m/s increments starting with 7m/s (inclination DP, 1.5°; V2, 2.5°). For DIAG, treadmill inclination was increased 1 ° every stage, starting at 6° with constant speed of 4.5m/s. Blood Lactate (LA), blood glucose and heart rate were measured. Subjects were video analyzed from the back view to determine CR, CL, poling and recovery time (PT+RT). Test was stopped when the subject passed a marker placed 1.5m from the front of the treadmill. To determine fatigue effects, the first 4 cycles were compared with the last 4 cycles. For changes across speed repeated ANOVA, and for determination of relationships Pearson product-moment correlations was calculated. In case of non-linear relationships, the best fit regression model was taken and the coefficient of determination (R²) presented. RESULTS: In all three techniques athletes adapted to increasing intensity by decrease in PT, RT and increase of CR (P<0.01). With V2, CL stayed constant over all speeds. Through 8.5m/s In DP and 8° in DIAG CL stayed constant, where after it decreased (P<0.01). At Vmax PT decreased to 210±12ms in DP and 180±15ms in V2. With fatigue, athletes increased CR, and decreased CL and RT (P<0.01). Only peak LA showed correlations to the respective V™, (r=0.49-0.83). In DP body height and pole length showed a low correlation to Vmax (r~0.45). Up to 8.5m/s in V2 and 10° in DIAG moderate to high correlations were found between CR (r~-0.66 to -0.88), CL and RT (r~0.66-0.83). In DP, through 7.9m/s low correlations were found for CR (r~-0.5), CL and RT (r~0.5). From that speed forth an increasing non-linear quadratic relationship was observed (8.2m/s R²=0.62; 8.5m/s R²=0.73), showing optimal CR and CL of around 1.20Hz and 7.5m, respectively. DISCUSSION: In all measured techniques skiers controlled speed by increasing CR, while trying to maintain CL. Together with the positive correlation of Vmax to RT and CL & submaximal velocities, it might be suggested that faster skiers focus more on producing high leg and arm Impulses to achieve longer CL and RT. it can also be seen that in fatigued state skiers are no longer able to maintain CL and compensate by an increase in CR mainly done by shortening RT. The decrease of PT to 210ms in DP and 180ms in V2, stresses the irnportance of high force development and force production within B very short time period All these aspects should be considered in modern strength and technique training concepts Of note is that in DP the fastest skiers use more of optimal instead of extreme CL and CR.
© Copyright 2007 4th International Congress on Science and Skiing. Veröffentlicht von University of Salzburg. Alle Rechte vorbehalten.