Energetics and biomechanics of double poling in regional and high-level cross-country skiers.

Purpose:The aim of this study was to evaluate the energetics and the biomechanics of double poling technique (DP) in two groups of cross-country skiers.Methods:Eight high-level (HLG) and eight regional-level (RLG) skiers performed a 5-min sub-maximal DP trial, roller skiing on a treadmill at 14 km h−1 and 2°. Energetic cost (ECDP), center of mass (COM) vertical displacement range, body inclination (θ, i.e., the angle between the vertical line and the line passing through COM and a fixed pivot point identified at feet level) and mechanical work associated to COM motion were analyzed. Pole and joint kinematics, poling forces and cycle timing were also considered.Results:HLG showed lower ECDP than RLG, smaller COM vertical displacement range and mechanical work, whereas higher θ during the early part of the poling phase (P < 0.05). In HLG, pole inclination was higher, poling forces greater and cycle duration longer (P < 0.05). Considering all skiers, a forward multiple regression revealed that the maximum value of θ (θ max) and the minimum value of COM vertical displacement resulted the COM-related parameters that better predict ECDP (AdjR 2 = 0.734; P < 0.001). Moreover, θ max positively related to poling force integrals and cycle duration (P < 0.05).Conclusions:A pronounced body inclination during the early poling phase and a reduced COM vertical displacement range concur in explaining the differences in ECDP found between the groups and among the skiers. A mechanically advantageous motion of COM during DP improves poling effectiveness, reduces cycle frequency and the mechanical work sustained