Sprinting for the win in cross-country skiing: Pacing strategy, race tactics, and the finish sprint

Abstract

Sprint cross-country (XC) skiing involves whole-body exercise on varying terrain using different sub-techniques of the classical and skating styles. The competition involves one to four ~3 min races, where the qualifying sprint time-trial (STT) is followed by three subsequent heats, in which six skiers compete and the top-two qualify for the next round along with the two fastest remaining skiers. Although not examined specifically in previous research, the skiers race tactics, and the ability to generate a high finish sprint speed are well recognized determinants of sprint XC skiing performance. The overall objective of this thesis was to explore race tactics in sprint XC skiing by investigating within-race determinants of heat performance and finish sprint ability in on-snow competitions. In study 1, speed and kinematics during four simulated STTs performed with conservative (controlled start) and positive (hard start) pacing strategies in both styles in a randomized order was investigated in twelve male national-level sprint skiers. Approximately 85% of maximal speed (Vmax) was obtained in the finish sprint, with Vmax and %Vmax contributing similarly (R2 = 51-78%) to explain the overall variance in finish sprint speed. The differences in kinematic patterns between the Vmax bout and the STT finish sprint were 11-22% reduced cycle rate (CR) in both styles without any changes in cycle length (CL). In the classical style, the finish sprint speed was 3.6% faster with the conservative pacing compared with the positive pacing strategy (P < .001), and this difference was explained by higher CR. In comparison, the percentage difference in finish sprint speed between strategies in the skating style was the same, but this difference did not reach statistical significance. In study 2, speed, positioning, and kinematics in the heats of an international sprint XC skiing competition in the classical style was investigated in thirty male national to world-class level sprint skiers. The top-two finishers in each heat were ~4% slower in the heats compared to the STT (P < .001). On average, the skiers performed 10 overtakings per 100 m from the start to the last uphill segment, but only ~3 overtakings per 100 m in the last two segments in each heat. As much as 94% of the top-two finishing skiers positioned themselves at top-two before approaching the final uphill, in which the top-four finishers were generally faster than those ranked 5-6. Here, top-four employed 5.3% longer CL and 3.4% higher CR in the diagonal (DIA) sub-technique than skiers ranked 5-6. A relatively similar technique distribution across skiers was observed within and between heats. In study 3, the influence of positioning on performance in 16 sprint XC skiing competitions and its consistency over repeated competitions on the same racecourse was investigated in male and female elite to world-class level sprint skiers. The STT rank correlated positively with the final rank for seven male (Ƥ =.54-.82, ƿ < .01) and eight female (ƿ = .40-.80, P < .05) competitions, while the STT rank and final rank did not correlate significantly in one of the classical competitions for men (P = .23). The strength of the correlation coefficients between intermediate ranks and final ranks during the heats increased gradually from the first to the last checkpoint among both sexes in the classical style (τ = ~0.24 to ~0.70) and in the skating style (τ = ~0.20 to ~0.84). In both sexes and styles, the heat winners positioned themselves gradually further towards the front of the heat with ~94% being ranked top-two at the last checkpoint before the finish sprint. For both sexes, an average of ~20 and ~16 overtakings were observed in each heat for the classical and skating style, respectively. There was a significant sex-difference in the number of overtakings in one out of the 16 competitions (P < .004), but no differences across seasons for competitions held on the same racecourse (P= .051-.796). This thesis provides new knowledge on pacing strategy, race tactics, and the finish sprint ability in sprint XC skiing. In study 1, the Vmax ability and the %Vmax contributed similarly to explain the finish sprint speed during the four simulated STTs, both in the classical and skating styles, and were independent of pacing strategy. Thus, sprint XC skiers should therefore concurrently develop both these capacities and employ technical strategies where a high CR can be sustained when fatigue occurs. In study 2, the main performance-determining factors in the heats of the international sprint XC skiing competition were a top-two position when approaching the final uphill segment in combination with higher speed by utilising longer CL and higher CR in DIA. In study 3, we found that the importance of being positioned at the front in the heats of international XC sprint skiing among men and women became more important the further into the racecourse, in which the majority of performance-variance was decided before the start of the finish sprint in both styles. The final rank for both sexes was decided at an earlier stage in the skating style compared to the classical style, which is likely explained by greater possibilities for positioning during the heats in the classical style. There were no significant differences in overtakings between seasons for competitions organized on the same type of racecourse with comparable conditions. Overall, this thesis shows the importance of finish sprint ability and positioning for performance in sprint XC skiing, with the number of overtakings being relatively consistent between competitions performed on the same racecourse. The practical implications are that an accurate racecourse analysis may help skiers to optimize their race-individual race-strategies in sprint XC skiing.