Struzik Artur, Zawadzki Jerzy
Department of Biomechanics, University School of Physical Education, Wrocław, Poland.
Acta Bioeng Biomech. 2013;15(2):113-8.
With respect to cyclic movements such as human gait, running or hopping, leg stiffness is a little variable parameter. The aim of this study was to investigate changes in leg stiffness during the phase of countermovement and take-off when performing a single maximum counter-movement jump. Kistler force plates and a BTS SMART system for comprehensive motion analysis were employed in the study. The study covered a group of 12 athletes from university basketball teams. Leg stiffness was calculated in those parts of countermovement and take-off phases where its level is relatively constant and the relationship F(Δl) is similar to linear one. Mean total stiffness (±SD) in both legs in the countermovement phase amounted to 6.5 ± 1.5 kN/m, whereas during the take-off phase this value was 6.9 ± 1 kN/m. No statistically significant differences were found between leg stiffness during the countermovement phase and takeoff phase in the study group at the level of significance set at α = 0.05. This suggests that the leg stiffness in phase of countermovement and phase of take-off are much similar to each other, despite different function of both phases. Similar to cyclic movements, leg stiffness turned out relatively constant when performing a single vertical jump. There are also reported statistically significant correlations between body mass, body height, length of lower limbs and leg stiffness. The stiffness analysed by the authors should be understood as quasi-stiffness because the measurements of ΔF(Δl) were made during transient states where inertia and dumping forces are likely to affect the final result.
对于诸如人类步态、跑步或跳跃等周期性运动而言，腿部刚度是一个略有变化的参数。本研究的目的是调查在进行单次最大反向运动跳跃时，反向运动和起跳阶段腿部刚度的变化情况。本研究采用了奇石乐测力板和用于综合运动分析的BTS SMART系统。该研究涵盖了一组来自大学篮球队的12名运动员。在反向运动和起跳阶段中，腿部刚度水平相对恒定且力与位移变化量（F(Δl)）的关系近似线性的那些部分计算腿部刚度。反向运动阶段双腿的平均总刚度（±标准差）为6.5±1.5 kN/m，而起跳阶段该值为6.9±1 kN/m。在显著性水平设定为α = 0.05时，研究组的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。这表明尽管两个阶段功能不同，但反向运动阶段和起跳阶段的腿部刚度彼此非常相似。与周期性运动类似，进行单次垂直跳跃时腿部刚度相对恒定。据报道，体重、身高、下肢长度与腿部刚度之间也存在统计学上的显著相关性。作者分析的刚度应理解为准刚度，因为力与位移变化量（ΔF(Δl)）的测量是在惯性和阻尼力可能影响最终结果的瞬态状态下进行的。
