Department of Biostatistics, Faculty of Medicine, University of Oslo, Oslo, Norway.
J Biomech. 2012 Jul 26;45(11):2014-8. doi: 10.1016/j.jbiomech.2012.05.014. Epub 2012 Jun 4.
When assessing reliability of three dimensional gait analysis, the coefficient of multiple correlation (CMC), a measure of similarity of waveforms, is frequently used. Several shortcomings of the method have been reported. It is strongly related to the range of motion (ROM); it is supposed to take values from 0 to 1, but is known to obtain complex values and break down. Removing offset before calculations appears to make it insensitive to apparent differences in gait. In the present work we use stochastic simulations to demonstrate why all of this happens, and the consequences thereof. We also demonstrate other, lesser-known, issues with the method, such as the strong dependency on number of subjects and test situations. The results are demonstrated on real data from an inter-rater repeatability study. We conclude that the CMC in its current form is generally unsuitable as a tool for assessing reliability in kinematic gait data.
在评估三维步态分析的可靠性时，通常使用复相关系数（CMC），这是一种衡量波形相似性的指标。该方法存在几个缺点已经被报道。它与运动范围（ROM）密切相关；其值应该在 0 到 1 之间，但已知会得到复杂的值并失效。在计算之前去除偏移量似乎会使它对步态的明显差异不敏感。在本工作中，我们使用随机模拟来演示为什么会发生这种情况，以及其后果。我们还演示了该方法的其他不太为人知的问题，例如对受试者数量和测试情况的强烈依赖性。结果在来自一个评分者间重复性研究的真实数据上进行了验证。我们得出结论，CMC 在其当前形式下通常不适合作为评估运动学步态数据可靠性的工具。
