title: Energetics and biomechanics of double poling in regional and high-level cross-country skiers.
abstract: OBJECTIVE
  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.
authors.affiliation: CeRiSM (Research Center Sport Mountain and Health), Via Matteo del Ben 5/b, Rovereto, 38068, Italy, chiara.zoppirolli@univr.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Zoppirolli
authors.forename: Barbara
authors.initials: B
authors.lastname: Pellegrini
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bortolan
authors.forename: Federico
authors.initials: F
authors.lastname: Schena
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D012865:Skiing / Q000502:physiology*
chemical_list: D019344:Lactic Acid