Author(s): UDA, S., MIYAMOTO, N., NAKANO, H., TAKEDA, M., Institution: DOSHISHA UNIVERSITY, Country: JAPAN, Abstract-ID: 1227

INTRODUCTION:
In cross-country skiing, competitions, sub-techniques exist in both classical and skating styles. The most appropriate sub-techniques are selected according to the gradient of the track, snow conditions, skiing velocity, or the athletes own physical fitness, such as muscle power. Classification of sub-techniques throughout the course could enhance performance analysis of the athletes, in turn, improve training plan for individual athlete. In this study, we used a high-precision kinematic global navigation satellite system (GNSS) (sampling frequency 100 Hz) to identify sub-technique in skating and clarify the characteristics of each sub-technique such as velocity, cycle length, cycle frequency, and gradient used.
METHODS:
Two subjects, an adult male skier and a junior high school male skier, were analyzed during a skating style time trial for 4.2 km. GNSS was attached to the skier’s head. Three-dimensional positional data of latitude, longitude, and altitude of the head during the time trial were acquired from a GNSS, and identification was made based on the difference in waveform patterns of vertical and horizontal movements of the head for each sub-technique. The sub-techniques of skating were classified into four categories: V1, V2, V2a, and Turn, and waveform patterns other than the four were classified as others. The applied skiing technique, skiing velocity, and cycle time and cycle length, gradient used for each technique were analyzed using the GNSS data. Motion data during trial was taken by Go pro video camera (Go pro, Hero 9) followed by snow mobile (ski-doo), which was used to confirm match ratio (%Match) with GNSS data.
RESULTS:
The %Match was high: 96.6% for V1, 98.2% for V2, 97.5% for V2a, 95.7% for Turn, and 97.1% in total. The percentage of each sub-technique used for all techniques was 25.8% for V1, 46.5% for V2, 14.3% for V2a, 13.3% for Turn 0.1% for others. The averages of skiing velocity, cycle time, cycle length, and gradient used for each sub-technique were calculated: for skiing velocity, V1: 4.05 m/sec, V2: 4.51 m/sec, V2a: 4.98 m/sec, and Turn: 5.01 m/sec; for cycle time, V1: 1.18 sec, V2: 1.09 sec, V2a: 1.41 sec, and Turn: 1.11 sec.; in cycle length, V1: 4.79 m, V2: 4.91 m, V2a: 7.10 m, and Turn: 5.55 m, in gradient used, V1: 2.71 degrees, V2: 1.01 degrees, V2a: -0.98 degrees, and Turn: -0.41 degrees.
CONCLUSION:
Based on the results of our study, it is suggested that a high-precision kinematic GNSS can be applied for discriminate sub-technique and clarify the usage characteristics of each sub-technique such as velocity, cycle length, cycle frequency, and slope used during a skating style XCS race.