Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada.
Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada.
Gait Posture. 2021 May;86:299-302. doi: 10.1016/j.gaitpost.2021.03.024. Epub 2021 Mar 26.
Surface translations are a method of perturbing an individual's balance to evoke balance control responses. However, the force plates used to measure kinetic responses often contain artifacts due to inertial properties coupled with the dynamics of surface translation perturbations. Techniques to attenuate these movement artifacts are not well established within the literature.
Are amplitude- or frequency-based subtraction processing techniques effective at attenuating inertia-based movement artifacts in kinetic signals during surface translations?
One-hundred and two backward surface translations were analyzed from five participants. Perturbation-matched unloaded pre-trials were collected to characterize force plate movement artifacts. For each trial, baseline data was processed to account for inertial artifacts using both amplitude- and frequency-based subtraction methods producing 3 datasets. Root mean square error (RMSE) between the datasets and expected tracings of an unloaded force plate were calculated. The effects of these processes on calculated knee flexion/extension (FE) moment were characterized using an inverse dynamics model which incorporated ground reaction forces and participant kinematics.
Both amplitude- and frequency-based processing methods resulted in near identical changes and substantially reduced RMSE values compared to original data. An RMSE reduction of 91.4 % was observed for the unloaded force channel which aligned with the direction of translation. Peak stance knee FE moments decreased by an average of 3.7 Nm and the average largest difference between the original data and both processing techniques across all trials was 30.4 Nm.
The results provide quantitative evidence that both data processing methods can successfully attenuate the presence of movement artifact found within force plate signals during surface translations. This study provides recommendations to researchers on effective methods for improving data processing techniques to attenuate force plate movement artifacts introduced by surface translations, towards more accurate estimates of joint kinetics during balance reactions.
表面平移是一种扰动个体平衡以引起平衡控制反应的方法。然而，用于测量动力学响应的力板通常由于惯性特性与表面平移扰动的动力学相结合而包含伪影。在文献中，没有很好地建立衰减这些运动伪影的技术。
基于幅度或频率的减法处理技术是否有效地衰减了表面平移过程中动力学信号中的基于惯性的运动伪影？
从五个参与者中分析了 102 个向后表面平移。收集了与加载预试验匹配的扰动，以描述力板运动伪影。对于每个试验，使用基于幅度和基于频率的减法方法处理基线数据以消除惯性伪影，从而产生 3 个数据集。计算数据集与空载力板的期望轨迹之间的均方根误差 (RMSE)。使用包含地面反作用力和参与者运动学的逆动力学模型来描述这些过程对计算的膝关节屈伸 (FE) 力矩的影响。
基于幅度和基于频率的处理方法都导致与原始数据相比，几乎相同的变化和大幅度降低的 RMSE 值。空载力通道的 RMSE 降低了 91.4%，与平移方向一致。峰值站立膝关节 FE 力矩平均减少了 3.7 Nm，并且在所有试验中原始数据和两种处理技术之间的平均最大差异为 30.4 Nm。
结果提供了定量证据，证明这两种数据处理方法都可以成功衰减在表面平移过程中力板信号中存在的运动伪影。本研究为研究人员提供了有关有效方法的建议，以改进数据处理技术，衰减由表面平移引入的力板运动伪影，从而更准确地估计平衡反应中的关节动力学。
