Delhaye Clément, Cross Matthew R, Bowen Maximilien, Samozino Pierre, Hintzy Frédérique
Univ. Savoie Mont Blanc, Inter-University Laboratory of Human Movement Biology, Chambéry, France.
Département Scientifique et Sportif, Fédération Française de Ski, Annecy, France.
Front Sports Act Living. 2020 Nov 25;2:589257. doi: 10.3389/fspor.2020.589257. eCollection 2020.
In alpine ski racing, different line choices can drastically affect turn or sectional performance. The straight-line transition between two turns is the main phase where skiers can gain speed in a race, open their trajectory, or reduce their path length. Between two turns, a skier can foster speed increase by spending more time in a straight line, inducing sharper turning phases (Z strategy). Inversely, speed can be conserved during the entire turn cycle by performing long curved turns separated by a short straight line (S strategy). This research aimed to evaluate the kinetic and kinematic specificities associated with the line strategy and to explore interactions of selected strategy with skier performance and energy dissipation. A mixed-level population of male alpine skiers ( = 17) skied a timed giant-slalom course while equipped with specialized force plates and a positional device collecting synchronized normal ground reaction force and position-time data, respectively. Time of edge switch was computed from the force signal as the period with the lowest force application on the outside ski. From positional data, turn cycles were separated into turning and straight-line phases (radius bellow and above 30 m, respectively). Time length, path length in the straight line, speed amplitude, and change in specific mechanical energy were computed for each turn and averaged for each skier. The path length during straight line was used to continuously characterize the line strategy within the spectrum between the Z (long straight line) and S (short straight line) strategy. Path length in the straight line was correlated with the amplitude of speed over a straight line ( = 0.672, = 0.003) and relative and absolute time spent in the straight line = 0.967 < 0.001). However, path length in straight line was not correlated with decrease of speed in the following turn ( = -0.418, = 0.390) or time without force application on the outside ski ( = 0.195, = 0.453). While higher-performing athletes on the course performed turns during which they dissipated less energy when normalized to entry speed ( = -0.620, = 0.008), it appears they did so with variable turn strategies approaches.
在高山滑雪比赛中，不同的线路选择会极大地影响转弯或分段表现。两个转弯之间的直线过渡阶段是滑雪者在比赛中能够加速、拓宽滑行轨迹或缩短滑行路径的主要阶段。在两个转弯之间，滑雪者可以通过在直线上花费更多时间来加快速度，进入更急的转弯阶段（Z策略）。相反，通过进行由短直线分隔的长弯道转弯（S策略），可以在整个转弯周期内保持速度。本研究旨在评估与线路策略相关的动力学和运动学特性，并探讨所选策略与滑雪者表现和能量耗散之间的相互作用。一组混合水平的男性高山滑雪者（n = 17）在配备专门测力板和位置装置的情况下，滑行了一场计时大回转比赛，分别收集同步的正常地面反作用力和位置-时间数据。根据力信号计算外侧雪板上力施加最低时期的刃转换时间。根据位置数据，将转弯周期分为转弯阶段和直线阶段（半径分别低于和高于30米）。计算每个转弯的时间长度、直线段路径长度、速度幅度和比机械能变化，并对每个滑雪者进行平均。直线段路径长度用于连续表征Z（长直线）和S（短直线）策略范围内的线路策略。直线段路径长度与直线段速度幅度相关（r = 0.672，p = 0.003），与在直线上花费的相对和绝对时间相关（r = 0.967，p < 0.001）。然而，直线段路径长度与下一个转弯的速度降低无关（r = -0.418，p = 0.390），也与外侧雪板无作用力的时间无关（r = 0.195，p = 0.453）。虽然在赛道上表现较好的运动员在转弯过程中，相对于进入速度的归一化能量耗散较少（r = -0.620，p = 0.008），但他们似乎采用了不同的转弯策略方法。
