Department of Sports Science and Physical Activity, University of Bedfordshire , Bedford, UK.
Sports Biomech. 2021 Feb;20(1):109-130. doi: 10.1080/14763141.2018.1460395. Epub 2018 May 16.
Stiffness describes the resistance of a body to deformation. In regard to athletic performance, a stiffer leg-spring would be expected to augment performance by increasing utilisation of elastic energy. Two-dimensional spring-mass and torsional spring models can be applied to model whole-body (vertical and/or leg stiffness) and joint stiffness. Various tasks have been used to characterise stiffness, including hopping, gait, jumping, sledge ergometry and change of direction tasks. Appropriate levels of reliability have been reported in most tasks, although they vary between investigations. Vertical stiffness has demonstrated the strongest reliability across tasks and may be more sensitive to changes in high-velocity running performance than leg stiffness. Joint stiffness demonstrates the weakest reliability, with ankle stiffness more reliable than knee stiffness. Determination of stiffness has typically necessitated force plate analyses; however, validated field-based equations permit determination of whole-body stiffness without force plates. Vertical, leg and joint stiffness measures have all demonstrated relationships with performance measures. Greater stiffness is typically demonstrated with increasing intensity (i.e., running velocity or hopping frequency). Greater stiffness is observed in athletes regularly subjecting the limb to high ground reaction forces (i.e., sprinters). Careful consideration should be given to the most appropriate assessment of stiffness on a team/individual basis.
僵硬度描述了物体抵抗变形的能力。就运动表现而言，人们期望更硬的腿部弹簧能够通过增加弹性能量的利用来提高表现。二维弹簧质量和扭转弹簧模型可用于模拟整个身体（垂直和/或腿部僵硬度）和关节僵硬度。各种任务都已用于描述僵硬度，包括跳跃、步态、跳跃、雪橇测功和变向任务。尽管不同的研究之间存在差异，但大多数任务的可靠性都得到了适当的报道。垂直僵硬度在所有任务中表现出最强的可靠性，并且可能比腿部僵硬度更能敏感地反映高速奔跑性能的变化。关节僵硬度表现出最低的可靠性，其中踝关节僵硬度比膝关节僵硬度更可靠。确定僵硬度通常需要进行力板分析；然而，经过验证的基于现场的方程允许在没有力板的情况下确定整个身体的僵硬度。垂直、腿部和关节僵硬度的测量都与性能测量结果相关。随着强度的增加（即跑步速度或跳跃频率），通常会表现出更大的僵硬度。在经常承受高地面反作用力的运动员（如短跑运动员）中观察到更大的僵硬度。应仔细考虑在团队/个人基础上最适当的僵硬度评估。
