Struzik Artur, Zawadzki Jerzy
Department of Team Sport Games, University School of Physical Education, Wrocław, Poland.
Department of Biomechanics, University School of Physical Education, Wrocław, Poland.
Acta Bioeng Biomech. 2016;18(2):163-71.
The aim of this study was to present the methodology for estimation of a leg stiffness during a countermovement jump. The question was asked whether leg stiffness in the countermovement and take-off phases are similar to each other as demonstrated in previous reports. It was also examined whether the stiffness in left lower limb is similar to the one in right lower limb.
The research was conducted on 35 basketball players. Each participant performed three countermovement jumps with arm swing to the maximum height. Measurements employed a Kistlerforce plate and a BTS SMART system for motion analysis. Leg stiffness (understood as an inclination of the curve of ground reaction forces vs. length) was computed for these parts of countermovement and take-off phases where its value was relatively constant and F(Δl) relationship was similar to linear.
Mean value (±SD) of total stiffness of both lower limbs in the countermovement phase was 7.1 ± 2.3 kN/m, whereas this value in the take-off phase was 7.5 ± 1 kN/m. No statistically significant differences were found between the leg stiffness in the countermovement and the take-off phases. No statistically significant differences were found during the comparison of the stiffness in the right and left lower limb.
The calculation methodology allows us to estimate the value of leg stiffness based on the actual shape of F(Δl) curve rather than on extreme values of ΔF and Δl. Despite different tasks of the countermovement and the take-off phases, leg stiffness in these phases is very similar. Leg stiffness during a single vertical jump maintains a relatively constant value in the parts with a small value of acceleration.
本研究旨在介绍一种在反向运动跳跃过程中估算腿部刚度的方法。研究的问题是，反向运动和起跳阶段的腿部刚度是否如先前报告所示彼此相似。同时还研究了左下肢的刚度与右下肢的刚度是否相似。
对35名篮球运动员进行了研究。每位参与者进行三次伴随手臂摆动至最大高度的反向运动跳跃。测量采用了奇石乐测力板和用于运动分析的BTS SMART系统。针对反向运动和起跳阶段中其值相对恒定且F(Δl)关系近似线性的部分，计算腿部刚度（理解为地面反作用力曲线与长度的斜率）。
反向运动阶段双下肢总刚度的平均值（±标准差）为7.1±2.3 kN/m，而起跳阶段该值为7.5±1 kN/m。反向运动阶段和起跳阶段的腿部刚度之间未发现统计学上的显著差异。左右下肢刚度比较时也未发现统计学上的显著差异。
该计算方法使我们能够根据F(Δl)曲线的实际形状而非ΔF和Δl的极值来估算腿部刚度值。尽管反向运动阶段和起跳阶段的任务不同，但这些阶段的腿部刚度非常相似。在单次垂直跳跃过程中，腿部刚度在加速度较小的部分保持相对恒定的值。
