Technique-Dependent Relationship between Local Ski Bending Curvature, Roll Angle and Radial Force in Alpine Skiing

by Selleckchem | May 28 2023

Skiing technique, and performance are impacted by the interplay between ski and snow. The resulting deformation characteristics of the ski, both temporally and segmentally, are indicative of the unique multi-faceted nature of this process. Recently, a PyzoFlex® ski prototype was presented for measuring the local ski curvature (w″), demonstrating high reliability and validity. The value of w″ increases as a result of enlargement of the roll angle (RA) and the radial force (RF) and consequently minimizes the radius of the turn, preventing skidding. This study aims to analyze segmental w″ differences along the ski, as well as to investigate the relationship among segmental w″, RA, and RF for both the inner and outer skis and for different skiing techniques (carving and parallel ski steering). A skier performed 24 carving and 24 parallel ski steering turns, during which a sensor insole was placed in the boot to determine RA and RF, and six PyzoFlex® sensors were used to measure the w″ progression along the left ski (w1-6″). All data were time normalized over a left-right turn combination. Correlation analysis using Pearson's correlation coefficient (r) was conducted on the mean values of RA, RF, and segmental w1-6″ for different turn phases [initiation, center of mass direction change I (COM DC I), center of mass direction change II (COM DC II), completion]. The results of the study indicate that, regardless of the skiing technique, the correlation between the two rear sensors (L2 vs. L3) and the three front sensors (L4 vs. L5, L4 vs. L6, L5 vs. L6) was mostly high (r > 0.50) to very high (r > 0.70). During carving turns, the correlation between w″ of the rear (w1-3″) and that of front sensors (w4-6″) of the outer ski was low (ranging between -0.21 and 0.22) with the exception of high correlations during COM DC II (r = 0.51-0.54). In contrast, for parallel ski steering, the r between the w″ of the front and rear sensors was mostly high to very high, especially for COM DC I and II (r = 0.48-0.85). Further, a high to very high correlation (r ranging between 0.55 and 0.83) among RF, RA, and w″ of the two sensors located behind the binding (w2″,w3″) in COM DC I and II for the outer ski during carving was found. However, the values of r were low to moderate (r = 0.04-0.47) during parallel ski steering. It can be concluded that homogeneous ski deflection along the ski is an oversimplified picture, as the w″ pattern differs not only temporally but also segmentally, depending on the employed technique and turn phase. In carving, the rear segment of the outer ski is considered to have a pivotal role for creating a clean and precise turn on the edge.

Comments：

This passage describes a study that analyzed the interplay between ski and snow in skiing technique and performance. The study used a PyzoFlex® ski prototype to measure the local ski curvature (w″) and investigate the relationship among segmental w″, roll angle (RA), and radial force (RF) for both inner and outer skis and different skiing techniques (carving and parallel ski steering).

The study involved a skier performing 24 carving and 24 parallel ski steering turns while wearing a sensor insole in the boot to determine RA and RF and six PyzoFlex® sensors to measure the w″ progression along the left ski (w1-6″). Data were time-normalized over a left-right turn combination, and correlation analysis was conducted on the mean values of RA, RF, and segmental w1-6″ for different turn phases (initiation, center of mass direction change I, center of mass direction change II, completion).

The study found that segmental w″ differed temporally and segmentally depending on the employed technique and turn phase. During carving turns, the rear segment of the outer ski was considered to have a pivotal role in creating a clean and precise turn on the edge. In contrast, for parallel ski steering, the correlation between the w″ of the front and rear sensors was mostly high to very high, especially for center of mass direction change I and II. Additionally, the study found a high correlation among RF, RA, and w″ of the two sensors located behind the binding in center of mass direction change I and II for the outer ski during carving but not during parallel ski steering.

Overall, this study provides insights into the complex interplay between ski and snow in skiing technique and performance, highlighting the importance of segmental w″ differences along the ski and the influence of different skiing techniques and turn phases.