Faculty of Behavioural and Movement Sciences, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, THE NETHERLANDS.
Norwegian Olympic Federation, Oslo, NORWAY.
Med Sci Sports Exerc. 2023 Jul 1;55(7):1241-1249. doi: 10.1249/MSS.0000000000003147. Epub 2023 Mar 18.
Force-velocity profiling has been proposed in the literature as a method to identify the overall mechanical characteristics of lower extremities. A force-velocity profile is obtained by plotting for jumps at different loads the effective work as a function of the average push-off velocity, fitting a straight line to the results, and extrapolating this line to find the theoretical maximum isometric force and unloaded shortening velocity. Here we investigated whether the force-velocity profile and its characteristics can be related to the intrinsic force-velocity relationship.
We used simulation models of various complexity, ranging from a simple mass actuated by a linearly damped force to a planar musculoskeletal model comprising four segments and six muscle-tendon complexes. The intrinsic force-velocity relationship of each model was obtained by maximizing the effective work during isokinetic extension at different velocities.
Several observations were made. First, at the same average velocity, less effective work can be done during jumping than during isokinetic lower extremity extension at this velocity. Second, the intrinsic relationship is curved; fitting a straight line and extrapolating it seem arbitrary. Third, the maximal isometric force and the maximal velocity corresponding to the profile are not independent. Fourth, they both vary with inertial properties of the system.
For these reasons, we concluded that the force-velocity profile is specific for the task and is just what it is: the relationship between effective work and an arbitrary estimate of average velocity; it does not represent the intrinsic force-velocity relationship of the lower extremities.
文献中提出了力-速度分析，作为一种识别下肢整体力学特性的方法。通过在不同负荷下绘制跳跃的有效功与平均蹬伸速度的关系图，可以得到力-速度曲线，拟合一条直线，并将其外推以找到理论上的最大等长力和空载缩短速度。在这里，我们研究了力-速度曲线及其特征是否与内在的力-速度关系相关。
我们使用了各种复杂程度的模拟模型，从由线性阻尼力驱动的简单质量到包含四个节段和六个肌肉-肌腱复合体的平面骨骼肌肉模型。每个模型的内在力-速度关系通过在不同速度下最大化等速伸展过程中的有效功来获得。
我们观察到了以下几点。首先，在相同的平均速度下，跳跃过程中的有效功比等速下肢伸展过程中的有效功少。其次，内在关系是弯曲的；拟合直线并外推似乎是任意的。第三，最大等长力和与曲线相关的最大速度不是独立的。第四，它们都随系统的惯性特性而变化。
由于这些原因，我们得出结论，力-速度曲线是特定于任务的，它只是有效功与任意平均速度估计之间的关系；它不代表下肢的内在力-速度关系。
