Background

In the field of three-dimensional motion analysis of the foot, there is little agreement on the preferred size of markers to record kinematic parameters. Although currently applied marker sizes show a considerable range, there has been no detailed investigation of the effect of marker size on the calculation of foot kinematics in the current literature.

Research question

The objective of this research was to determine whether marker size impacts essential parameters that describe foot biomechanics.

Methods

Seventeen subjects participated in this randomized repeatability study. All participants had to walk on a treadmill twice to test two sets of markers (set A: small marker, 9.5 mm, 1 g; set B: large marker, 14 mm, 2 g). Three-dimensional motion capturing was used to record the trajectories of the markers. The spatial relation of the markers, as well as vertical motion of the navicular bone and the angle of the medial longitudinal arch were calculated based on the marker trajectories. In addition to motion capturing, skin rigidity was quantified by applying an oscillatory shear force to the skin. Analysis of variance, root-mean-square error calculations and linear fit methods were applied to evaluate effects of marker size on the calculation of foot kinematics and the impact of skin rigidity.

Results

The estimated foot kinematics appeared to be unaffected by the size of the markers. Further, there was no evidence that skin rigidity influenced the error of the marker trajectories. Interestingly, the large markers fell off more frequently.

Significance

The findings will be of interest to those who use marker-based three-dimensional motion capturing, especially to analyze foot biomechanics. Although the calculation of kinematic parameters appears to be unaffected by marker size, practical aspects, like accidental marker loss, favor the application of small markers.

中文翻译：

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标记大小对脚部三维运动分析的影响。

背景

在脚的三维运动分析领域，关于记录运动学参数的标记的首选尺寸几乎没有共识。尽管当前应用的标记尺寸显示出相当大的范围，但是在当前文献中，没有对标记尺寸对足运动学计算的影响进行详细研究。

研究问题

这项研究的目的是确定标记物的大小是否影响描述足部生物力学的基本参数。

方法

十七名受试者参加了这项随机可重复性研究。所有参与者都必须在跑步机上行走两次以测试两组标记（A组：小标记，9.5毫米，1克； B组：大标记，14毫米，2克）。使用三维运动捕捉来记录标记的轨迹。根据标记物的轨迹计算标记物的空间关系，以及颌骨的垂直运动和内侧纵弓的角度。除了运动捕捉之外，还通过向皮肤施加振荡剪切力来量化皮肤刚度。方差分析，均方根误差计算和线性拟合方法用于评估标记物大小对脚运动学计算和皮肤刚度影响的影响。

结果

估计的脚运动学似乎不受标记物大小的影响。此外，没有证据表明皮肤刚度会影响标记轨迹的误差。有趣的是，大标记掉落的频率更高。

意义

使用基于标记的三维运动捕捉，尤其是分析足部生物力学的人们将对这一发现感兴趣。尽管运动学参数的计算似乎不受标记大小的影响，但实际的方面（如意外丢失标记）有利于小标记的应用。