Nilsson Johnny, Jakobsen Vidar, Tveit Per, Eikrehagen Olav
Norwegian University of Sport and Physical Education, Oslo, Norway.
Sports Biomech. 2003 Jul;2(2):227-36. doi: 10.1080/14763140308522820.
The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross-country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: 'short', self-selected (normal) and 'long'. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self-selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s-1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (F2), anterior-posterior (Fy) and mediolateral (Fx) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3-D by an opto-electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior-posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior-posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior-posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior-posterior force impulse and velocity.
本研究的目的是探讨越野滑雪双杖滑行时，蹬杖阶段时长、地面反作用力、蹬杖后速度增加量与杖长及杖角度之间的关系。七名男性地区精英越野滑雪运动员自愿参与本研究。受试者使用三种不同长度的滑雪杖进行最大双杖蹬地动作：“短”杖，自选（正常）长度杖和“长”杖。短杖比自选杖短7.5厘米，长杖比自选杖长7.5厘米。受试者对每种杖长进行七次最大蹬杖动作，这些动作在21次试验中随机选取。每次试验中，受试者从1.2米高的下坡加速，在到达位于坡底的测力板上进行最大双杖蹬地动作前达到3.92米/秒的速度。测力板测量左杖的垂直（F2）、前后（Fy）和内外侧（Fx）反作用力。通过光电系统以三维方式记录滑雪杖的位置。根据记录的数据计算蹬杖阶段时长、冲量、平均力、蹬杖后速度增加量和杖角度。使用长杖进行双杖滑行产生的前后推进反作用力冲量和速度增加量显著大于正常杖（p < .05）和短杖（p < .05）。尽管短杖产生的平均前后反作用力更大。因此，蹬杖阶段时长是决定前后推进冲量的主要因素。对于从业者而言，当目标是增加蹬杖阶段时长、前后力冲量和速度时，这些结果在选择杖长方面可能会有所帮助。
