St, Mary's University College and Department of Bioengineering, Imperial College London, UK.
Biomed Eng Online. 2010 Nov 17;9:74. doi: 10.1186/1475-925X-9-74.
A vast number of biomechanical studies have employed inverse dynamics methods to calculate inter-segmental moments during movement. Although all inverse dynamics methods are rooted in classical mechanics and thus theoretically the same, there exist a number of distinct computational methods. Recent research has demonstrated a key influence of the dynamics computation of the inverse dynamics method on the calculated moments, despite the theoretical equivalence of the methods. The purpose of this study was therefore to explore the influence of the choice of inverse dynamics on the calculation of inter-segmental moments.
An inverse dynamics analysis was performed to analyse vertical jumping and weightlifting movements using two distinct methods. The first method was the traditional inverse dynamics approach, in this study characterized as the 3 step method, where inter-segmental moments were calculated in the local coordinate system of each segment, thus requiring multiple coordinate system transformations. The second method (the 1 step method) was the recently proposed approach based on wrench notation that allows all calculations to be performed in the global coordinate system. In order to best compare the effect of the inverse dynamics computation a number of the key assumptions and methods were harmonized, in particular unit quaternions were used to parameterize rotation in both methods in order to standardize the kinematics.
Mean peak inter-segmental moments calculated by the two methods were found to agree to 2 decimal places in all cases and were not significantly different (p > 0.05). Equally the normalized dispersions of the two methods were small.
In contrast to previously documented research the difference between the two methods was found to be negligible. This study demonstrates that the 1 and 3 step method are computationally equivalent and can thus be used interchangeably in musculoskeletal modelling technology. It is important that future work clarifies the influence of the other inverse dynamics methods on the calculation of inter-segmental moments. Equally future work is needed to explore the sensitivity of kinematics computations to the choice of rotation parameterization.
大量的生物力学研究采用逆动力学方法来计算运动过程中的节段间力矩。尽管所有的逆动力学方法都植根于经典力学，因此在理论上是相同的，但存在着许多不同的计算方法。最近的研究表明，逆动力学方法的动力学计算对计算出的力矩有重要影响，尽管这些方法在理论上是等效的。因此，本研究的目的是探讨逆动力学选择对节段间力矩计算的影响。
使用两种不同的方法对垂直跳跃和举重运动进行逆动力学分析。第一种方法是传统的逆动力学方法，在本研究中被称为三步法，其中节段间力矩是在每个节段的局部坐标系中计算的，因此需要进行多次坐标系变换。第二种方法（一步法）是最近提出的基于力和矩符号的方法，允许在全局坐标系中进行所有计算。为了最好地比较逆动力学计算的影响，对一些关键假设和方法进行了协调，特别是在两种方法中都使用单位四元数来参数化旋转，以标准化运动学。
两种方法计算得到的平均峰值节段间力矩在所有情况下都相差两位小数，并且没有显著差异（p＞0.05）。两种方法的归一化分散度也很小。
与之前的研究结果相反，两种方法之间的差异可以忽略不计。本研究表明，一步法和三步法在计算上是等效的，因此可以在肌肉骨骼建模技术中互换使用。未来的工作需要澄清其他逆动力学方法对节段间力矩计算的影响，同样需要探索运动学计算对旋转参数化选择的敏感性。
