# The Contribution of Ski Poles to Aerodynamic Drag in Alpine Skiing
###### Abstract  
The present study was designed to determine the contribution of the cross-sectional area of the ski poles (S\({}_{\rm p}\)) to the total aerodynamic drag during alpine skiing. At three different wind speeds in a wind tunnel, 10 skiers assumed typical alpine skiing postures (high, middle, and tuck), and their frontal aerodynamic drag was assessed with a force plate and their cross-sectional area, along with that of their ski poles, determined by interactive image segmentation. The data collected were utilized to examine intra-subject variation in S\({}_{\rm p}\), the effects of S\({}_{\rm p}\) on the coefficient of aerodynamic drag (C\({}_{\rm d}\)), and the product of C\({}_{\rm d}\) and total cross-sectional area (C\({}_{\rm d}\)'S. The major findings were as follows: (i) S\({}_{\rm p}\) ranged from 0.0067 (tuck position) to 0.0262 m\({}^{2}\) (middle position), contributing 2.2-4.8% of the total cross-sectional area, respectively; (ii) S\({}_{\rm p}\) was dependent on wind speed in the high and middle positions; (iii) intra-subject variations ranged from 0.0018 m\({}^{2}\) (27.6%) in the tuck position to 0.0072 m\({}^{2}\) (30.5%) in the high position; (iv) S\({}_{\rm p}\) exerted a likely effect on C\({}_{\rm d}\) and C\({}_{\rm d}\)'S. The extensive intra- and inter-skier variability in S\({}_{\rm p}\) can account for as much as \(\sim\)5% of the total frontal cross-sectional area and future investigations on how elite skiers optimize their positioning of the poles in a manner that reduces aerodynamic drag are warranted. air resistance; biomechanics; force; kinetics; cross-sectional area; coefficient of aerodynamic drag; wind tunnel; skiing position; ski posture; tuck +
Footnote †: journal: Applied Sciences  
1 Faculty of Sport, University of Ljubljana, 1000 Ljubljana, Slovenia 1  
[PERSON], 4  
Footnote †: journal: Applied Sciences  
Footnote 1:Clearly, the downhill and super-giant slalom, with their considerably higher speeds, involve more aerodynamic drag than slalom and giant slalom [10; 11]. In light of the fact that the difference between the finishing times of elite alpine skiers competing for medals is often on the order of hundredths of a second [12], even very minor optimization of aerodynamic drag can be decisive. To measure aerodynamic drag in connection with alpine ski racing, several experimental approaches have been developed for both speed [13; 14; 15] and technical disciplines [5; 6; 16]. Assessment of the coefficient of aerodynamic drag (C\({}_{\rm d}\)) and cross-sectional area (S), as well as C\({}_{\rm d}\cdot\)S, the product of these two, in wind tunnels have attempted to optimize body posture, showing that height, joint angles, and positioning of the arms and head all influence the aerodynamic drag [5; 6; 16]. Moreover, C\({}_{\rm d}\cdot\)S for the technical disciplines ranged from 0.63-0.66 in the high, 0.51-0.55 in the middle, and 0.23-0.24 in the tuck positions, which is generally lower than the corresponding values reported for the speed disciplines (0.15-0.4) [8; 13]. Investigation of different body postures in a wind tunnel demonstrated that aerodynamic drag was 41% less with the arms in a tuck position than stretched out (as when jumping) [17]. Although the ski poles are positioned more or less transverse to the wind flow during the performance of all of the technical disciplines, including during the intensive turning involved in the speed disciplines (see, for example, Figure 1) and the poles (typically 120-135 cm in length for male skiers) are considerably longer than the arms and have baskets, their impact on aerodynamic drag remains largely unexplored. Accordingly, the contribution of the ski poles to total aerodynamic drag in connection with various postures during alpine skiing at different speeds was assessed here in a wind tunnel.