Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength

Abstract

The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large.

Sport-specific balance tests account for youth alpine skiers’ ranking

“…The current results also mirror the demands faced by alpine skiers, where effective balance and motor control are required to cope with course setting, terrain variety, and snow conditions ( Gilgien et al, 2018 ). Therefore, in agreement with present results and previous findings, we can speculate that the better dynamic balance of high-ranking skiers could be a factor that can exert considerable influence on the successful performance of alpine ski racers ( Ogrin et al, 2021 ). Our results contrast with those of Noè and Paillard who reported similar static and sport-specific balance performances in skiers at regional and national levels ( Noé and Paillard, 2005 ), and support previous research on the use of sport-specific dynamic balance tests to ensure the proper selectivity among athletes ( Asseman et al, 2008 ).…”

“…Our findings indicated that the dominant and non-dominant limbs equally contributed to the management of the SST ( Table 4 ; Figure 4 ) independently from the skiers’ ranking level. However, the high-ranking group expressed the best balance performance ( Table 2 ) despite the magnitude of ground reaction forces while turning on-snow is different for the inner and the outer leg ( Ogrin et al, 2021 ). Again, we can speculate that high-ranking skiers adopted more effective control strategies to overcome the constraints at the ankle joint.…”

“…Furthermore, in alpine skiing turning, there are large asymmetries in ground reaction forces between the inside and outside leg. However, these asymmetries are not related to asymmetries in skiers’ muscular strength ( Ogrin et al, 2021 ). Alpine skiing requires also complex motor skills and fine adjustments to maintain balance in challenging conditions ( Schaff and Hauser, 1989 ; Raschner et al, 2017 ).…”

Unilateral Maximal Isometric Hex Bar Pull Test: Within-Session Reliability and Lower Body Force Production in Male and Female Freeski Athletes

“…These findings could therefore be of potential interest for practitioners working with freeski populations. However, unilateral strength measurement values recorded in the laboratory may not be correlated to the ground reaction force kinetics in the sport (Ogrin et al, 2021 ). Further research is required to determine a detailed physiological and neuromuscular profile of academy to elite freeski athletes.…”

Influence of Turn Cycle Structure on Performance of Elite Alpine Skiers Assessed through an IMU in Different Slalom Course Settings

“…There is no consensus on the number of phases into which a turn should be divided. There are authors who have divided the turn into two [4][5][6][7], three [2,3,[8][9][10] or four phases [11,12]. However, most studies agree on a fundamental division on two phases within the turn: the initiation (INI) phase, described as the motion between turns where lateral forces are non-existent, and…”