Biomechanical Analysis of Double Poling in Elite Cross-Country Skiers

Abstract

DP was found to be a complex movement involving both the upper and lower body showing different strategies concerning several biomechanical aspects. Future research should further investigate the relationship between biomechanical and physiological variables and elaborate training models to improve DP performance.

Biomechanics of simulated versus natural cross-country sit skiing

“…The first peak occurred at the impact, while the second is related to propulsion. Compared to able-bodied athletes who showed lower impact force with respect to peak force (Holmberg et al 2005), XC sit-skiers impact force was higher in both conditions. This higher impact force may be due to the sitting position and the ability of the athlete to take advantage of the force of gravity when poling, which influences the inclination of the pole at ground contact and subsequently the force transmitted to the ground at the impact through each pole.…”

“…As a result, the first part of elbow flexion in the propulsion phase might be similar to a pull-up movement ). This greater range of motion in the upper limbs could also explain the higher peak and average muscle activity for Latissimus during the poling phases in simulated compared to the natural conditions because of its extensor function in the first part of the poling phase (Holmberg et al 2005). Moreover, a greater trunk flexion in simulated conditions during the poling phase could explain the higher Rectus Abdominis activation, which indicates better stability.…”

“…However, to verify this assumption, the direction of the force application should be measured. The impact force induced a pre-activation of Pectoralis and Rectus Abdominis ( Figure 3A) to increase the muscle stiffness in order to prepare the body for the pole impact, and stabilizes the involved joints to generate more propulsion at the beginning of the poling phase similar to able-bodied skiers (Holmberg et al 2005).…”

“…For each cycle the average muscle activity (aEMG) and the muscle activity peak (EMG peak ) were calculated on the rectified signals and on the linear envelope respectively (Holmberg et al 2005). Since the minimum number of good cycles available for all the athletes was lower than seven, neuromuscular variables were calculated from five out of seven consecutive propulsion cycles.…”

“…Although many studies have been conducted on the physiology (Hoffmann et al 1991;Pellegrini et al 2013), biomechanics (Millet et al 1998a(Millet et al , 1998bHolmberg et al 2005Holmberg et al , 2006Stöggl and Holmberg 2011;Zoppirolli et al 2015), and neuromuscular activity (Holmberg et al 2005) of able-bodied skiers in DP, very few studies have assessed this technique in sitskiing. Bernardi et al (2013) evaluated changes in speed and kinematic parameters during flat and uphill tracks, finding an average cycle duration of 0.98 s and 0.84 s respectively, while Gastaldi et al (2012Gastaldi et al ( , 2014Gastaldi et al ( , 2016, investigated DP kinematics in sit-skiing athletes belonging to different classes using a markerless kinematic analysis.…”