Kinematic differences between uphill roller skiing and on-snow skiing using the V2 skating technique

Abstract

Purpose: Roller skiing is the primary sport-specific training and testing mode during pre-competition periods for cross-country skiers, biathletes, and Nordic combined athletes. The present study aimed to compare the kinematics between uphill roller skiing and on-snow skiing using the V2 sub-technique.

Methods: In a cross-over design, nine well-trained male skiers performed short trials (< 40 s) at constant inclination (8.0°), speed (3.0 m‧s^-1), and controlled rolling/gliding friction on asphalt (in the fall), on the treadmill (in the fall and winter), and during on-snow skiing (in the winter). Kinematic data were collected using a validated inertial measurement unit system.

Results: Repeated-measures ANOVAs revealed no differences between treadmill and asphalt roller skiing. Further, including on-snow skiing showed moderate to good reliability (ICC ≥ 0.63, p ≤ 0.001) for ground-contact temporal variables. However, on-snow skiing moderately increased hip range of motion around the longitudinal axis (22.2 ± 7.7° vs. 14.1 ± 4.7°), lateral hip displacement (44.1 ± 7.1 cm vs. 37.2 ± 6.6 cm) and pole push times (422 ± 41 ms vs. 386 ± 31 ms), and on-snow skiing was characterized by altered hip rotational patterns compared to roller skiing.

Conclusion: V2 roller ski skating simulates on-snow ski skating to a large extent, but the mechanical properties of the skis and/or surface hardness systematically alter skiers' hip movements and pole push times. This implies a potential for equipment optimization to increase training specificity during pre-competition periods and highlights a need for future studies to examine the kinematic effects of snow hardness on all sub-techniques.

Keywords: Accelerometer; Gear 3; Gyroscope; Inertial sensors; Training specificity; Validity.

Fig. 1

Upper: One full cycle of the V2 technique. Lower: The 30 m outdoor data-collection area, marked with lines and poles every 7.5 m. Photocells at fixed distances for calculating gliding friction and an anemometer for wind measurement can be seen to the left

Fig. 2

Time-normalized group-averaged displacement patterns for the three roller-ski tests (black lines) and 90% confidence limits for the on-snow skiing test (filled area). Magnitudes of confidence limits were similar for all tests. Vertical lines indicate pole thrusts and cycle starts with pole plants when standing on the right ski. N = 9

Fig. 3

Time-normalized group-averaged rotation patterns for the three roller-ski tests (black lines), and 90% confidence limits for the on-snow skiing test (filled area). Positive X, Y, and Z-angles indicate the pelvis to be backward tilted, laterally tilted to the right, and heading to the left, respectively, compared to the average orientation of the pelvis within the cycle. Magnitudes of confidence limits were similar for all tests. Vertical lines indicate pole thrusts and cycle starts with pole plants when standing on the right ski. N = 9

Fig. 4

Time-normalized group-averaged acceleration patterns for the three roller-ski tests (black lines), and 90% confidence limits for the on-snow skiing test (filled area). Magnitudes of confidence limits were similar for all tests. Vertical lines indicate pole thrusts and cycle starts with pole plants when standing on the right ski. N = 9