Zoppirolli Chiara, Pellegrini Barbara, Bortolan Lorenzo, Schena Federico
CeRiSM (Research Center Sport Mountain and Health), Via Matteo del Ben 5/b, Rovereto, 38068, Italy,
Eur J Appl Physiol. 2015 May;115(5):969-79. doi: 10.1007/s00421-014-3078-4. Epub 2014 Dec 17.
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.
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.
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).
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.
本研究旨在评估两组越野滑雪运动员双杖滑雪技术（DP）的能量学和生物力学。
8名高水平（HLG）和8名区域水平（RLG）的滑雪运动员进行了一次5分钟的次最大强度DP试验，在跑步机上以14 km/h(-1)和2°的坡度进行轮滑滑雪。分析了能量消耗（ECDP）、重心（COM）垂直位移范围、身体倾斜度（θ，即垂直线与通过COM和在脚部水平确定的固定枢轴点的直线之间的夹角）以及与COM运动相关的机械功。还考虑了杖和关节的运动学、撑杖力和周期时间。
HLG组的ECDP低于RLG组，COM垂直位移范围和机械功较小，而在撑杖阶段早期θ值较高（P < 0.05）。在HLG组中，杖的倾斜度更高，撑杖力更大，周期持续时间更长（P < 0.05）。考虑所有滑雪运动员，向前多元回归显示，θ的最大值（θ max）和COM垂直位移的最小值是能更好预测ECDP的与COM相关的参数（调整R(2)=0.734；P < 0.001）。此外，θ max与撑杖力积分和周期持续时间呈正相关（P < 0.05）。
撑杖阶段早期明显的身体倾斜和COM垂直位移范围的减小共同解释了两组之间以及滑雪运动员之间在ECDP上的差异。DP期间COM的机械优势运动提高了撑杖效率，降低了周期频率和承受的机械功。
