INTRODUCTION: In ski marathon races, it has been revealed that elite skiers tend to use double poling more frequently than amateurs [1]. However, it remains unclear to what extent double poling and other sub-techniques are used throughout the course, spanning several tens of kilometers. Recently, high-precision kinematic GNSS devices enabled the classification of subtechniques based on distinctive patterns of head movements [2]. This study aims to analyze the relationship between skiing speed and course slope for each sub-technique across a ski marathon race course based on the classification method. METHODS: In a 50 km classic style race (Reistadlopet), a kinematic GNSS device (AT-H-02, AOBA Technologia LLC) was mounted on the back of a male elite skier to obtain 5 Hz centimeter accurate positional data. Based on the classification method by Takeda et al. (2019) [2], subtechniques (DP, KDP, DIA, downhill) used by the subject were identified from vertical movements of the upper thoracic spine in this study. In addition, the skiing velocity and course inclination were analyzed, and the time and distance usage ratios for each sub-technique were calculated. RESULTS/DISCUSSION: The total race time was 2h31`41``, with the subject finishing 1st place. The average skiing speeds for each sub-technique were 6.49 m/s for DP, 4.15 m/s for KDP, 3.02 m/s for DIA, and 10.39 m/s for downhill. The average incline angles were 0.24° or DP, 3.36° for KDP, 6.73° for DIA, and -3.12° for downhill (Fig.1). The time usage ratios were 38.9% (59`1``) for DP, 12.9% (19`33``) for KDP, 31.5% (47`46``) for DIA, and 15.2% (23`1``) for downhill. The distance usage ratios were 43.9%(21.95km) for DP, 9.5%(4.75km) for KDP, 16.3%(8.15km) for DIA, and 29.1%(14.55km) for downhill. Since downhill was the 2nd highest distance usage ratio, it is evident that selecting skis and wax is crucial. The clear distribution pattern in Fig.1 indicates that the subject determined the sub-techniques based on skiing speed and incline angle, especially prioritized skiing speed rather than inclination angle. CONCLUSION: Throughout the race, DP proved to be the fastest technique and was the most frequently used in terms of both time and distance, followed by KDP and DIA. The findings of this study provide valuable insights into how elite athletes effectively utilize different techniques, which can contribute to improving future training programs and race strategies.
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