Forner-Cordero A, Koopman H J F M, van der Helm F C T
Institute for Biomedical Technology (BMTI), Biomedische Werktuigbouwkunde, CTW Gebouw, Universiteit Twente, PB 217 NL-7500 AE Enschede, The Netherlands.
J Biomech. 2006;39(5):948-57. doi: 10.1016/j.jbiomech.2005.01.019.
Traditionally, gait analysis has been based on normalizing the stride time to a percentage and then averaging several strides measured under the same conditions. This procedure relies on the questionable assumptions that gait is a cyclic movement with superimposed noise and that there is no variability in the timing of activation or in the angles within the stride so no rescaling occurs during the percentage conversion. However, there is a fluctuation in the timings at which the peak values occur. A typical hallmark of this time-rescaling is the increase of the joint angle standard deviation when the angular velocity increases. The goal of this paper is to present a description of gait to avoid averaging without distorting the original curves. In addition, it allows the analysis of the fluctuation between consecutive strides. In this method, it is assumed that gait is quasi-periodic. The key point is the representation of gait by a state vector that evolves in time. This state vector can be used to calculate the instantaneous period and provides a measure of the time fluctuations between strides. The sequence of states method describes a quasi-periodic movement like gait with a continuous estimate of cycle time and provides measure of the deviations between cycles.
传统上，步态分析是将步幅时间标准化为一个百分比，然后对在相同条件下测量的几个步幅进行平均。这个过程依赖于一些有问题的假设，即步态是一种叠加有噪声的循环运动，并且在步幅内激活时间或角度没有变化，因此在百分比转换过程中不会发生重新缩放。然而，峰值出现的时间存在波动。这种时间重新缩放的一个典型特征是当角速度增加时关节角度标准差的增加。本文的目的是给出一种步态描述，以避免平均化而不扭曲原始曲线。此外，它还允许分析连续步幅之间的波动。在这种方法中，假设步态是准周期性的。关键在于用一个随时间演化的状态向量来表示步态。这个状态向量可用于计算瞬时周期，并提供步幅之间时间波动的度量。状态序列法描述了一种类似于步态的准周期性运动，具有对周期时间的连续估计，并提供了周期之间偏差的度量。
