Departments of 1Track and Field and 2Biomechanics, University School of Physical Education in Wroclaw, Poland; and 3Department of Biomechanics, Faculty of Sport, University of Ljubljana, Slovenia.
J Strength Cond Res. 2013 Oct;27(10):2650-61. doi: 10.1519/JSC.0b013e31828909ec.
The purpose of this study was to investigate the effect of 2 strategies, defined by foot placement during the initiation of the take-off on performance in vertical jumps. The additional area of interest in this experiment was whether technique of the take-off phase might be an exploratory factor that has different electromyogram (EMG) muscle activity during squat jump (SJ) and countermovement jump (CMJ) performed starting from the standard position, with parallel foot placement, and from the experimental one, with straddle foot placement. Six well-experienced male 100-400 m sprinters, who were members of the Polish youth and senior national team (mean values: age 21.6 years, best performance: 100 m in 10.54 seconds and 400 m in 45.54 seconds), performed vertical SJ and vertical CMJ from 2 initial positions with different foot placement. To collect all selected kinematic and kinetic data, the video recording system BTS Vixta was used in conjunction with force platforms (Kistler model 9286B). The latest system for 3D motion analysis, BTS SMART, based on the passive IR reflective markers was also applied. Electromyograms of 6 lower limb muscles were collected using a Noraxon EMG device. The CMJ was on average 7 cm higher than the SJ (CMJ, 85 cm and SJ, 78 cm), which amounts to 8.97%. This was not because of the increase of center of gravity (COG) velocity at take-off because velocities of center of gravity (COG) projection were almost equal (SJ, 2.93 m·scompared with CMJ, 2.99 m·s). No significant differences of both magnitude and rate of development of the muscle torques and powers between jumps were found, but when we analyzed the problem with division into single legs (right and left) and with division into different jumps (SJ and CMJ), the differences were evident. The profiles of EMG activity of selected muscles showed some differences between SJ and CMJ. The vertical SJ and CMJ performance measurement may be of value to coaches and conditioning specialists who wish to develop or assess the power ability of lower extremities either unilaterally (single leg) or bilaterally (sum of both legs).
本研究的目的是探讨在起跳阶段脚部位置的 2 种策略对垂直跳跃表现的影响。本实验的另一个关注领域是起跳阶段的技术是否可能是一个探索性因素，在从标准位置、平行脚位开始进行的深蹲跳（SJ）和反向跳（CMJ）中，具有不同的肌电图（EMG）肌肉活动，以及从实验位置、分腿脚位开始进行的 SJ 和 CMJ。6 名经验丰富的男性 100-400 米短跑运动员，他们是波兰青年队和成年国家队的成员（平均值：年龄 21.6 岁，最佳成绩：100 米 10.54 秒，400 米 45.54 秒），从 2 种不同脚部位置的初始位置进行了垂直 SJ 和垂直 CMJ。为了收集所有选定的运动学和动力学数据，使用 BTS Vixta 视频记录系统与力台（Kistler 模型 9286B）相结合。还应用了最新的基于被动红外反射标记的 3D 运动分析系统 BTS SMART。使用 Noraxon EMG 设备采集 6 条下肢肌肉的肌电图。CMJ 比 SJ 高 7 厘米（CMJ，85 厘米，SJ，78 厘米），高 8.97%。这不是因为起跳时重心（COG）速度的增加，因为 COG 速度的投影几乎相等（SJ，2.93 m·s，与 CMJ，2.99 m·s）。没有发现跳跃之间肌肉扭矩和功率的大小和发展速度的显著差异，但当我们将问题分为单腿（右腿和左腿）和不同跳跃（SJ 和 CMJ）进行分析时，差异就很明显了。选定肌肉的 EMG 活动曲线显示 SJ 和 CMJ 之间存在一些差异。垂直 SJ 和 CMJ 性能测量可能对教练和体能专家有价值，他们希望发展或评估下肢的力量能力，无论是单侧（单腿）还是双侧（双腿总和）。
