Vicon ProCalc 6DOF Modeling Tutorial

About this tutorial

This tutorial explains how to:

• Use the Vicon ProCalc software to create a simple 6-degrees-of-freedom model based on cluster markers attached to shoes as well as anatomical markers used in the static trial only.
• Automatically define foot strike and foot off events for a trial where a subject runs on a treadmill.
• Extract relevant parameters that characterize the motion.

After you complete this tutorial, you will understand the workflow involved in defining a 6-degrees-of-freedom model based on a very simple marker set. Of course, most biomechanical models are more complicated than this one, but using what you have learned here as the basis, you can expand this to include other segments.

About the data for this tutorial

To follow this tutorial, navigate to C:\Program Files\Vicon\ProCalc\Help and unzip the ProCalc Tutorials Data file. Choose a path or directory that has sufficient read/write permissions and that you can remember and access easily (eg, C:\Users\Public\Documents\Vicon). If you have completed a ProCalc tutorial in the past, you may have already completed this step.

For this tutorial, we will use the 6DOF Data session. Within this folder, there are two trials:

• Static.c3d
• Running.c3d

In addition, two Vicon subject files are included:

• Feet.mp
• Feet.vsk

To access the trials in ProCalc, ensure you have a hierarchy that looks like the example below, though the specific path will depend on the location of your extracted data.

The model used for this tutorial is as simple as possible. Three markers are attached to the heel of each shoe asymmetrically – two are placed vertically with respect to one another on the most posterior aspect of the shoe, and the third one is placed laterally and asymmetrically, so that the distances of the three sides in the triangle formed by the markers are all different. Two further markers are placed, on the lateral and medial malleolae, respectively. These define the ankle joint center and the ankle flexion/extension axis.

The aim is to use this simple marker set and model to calculate foot strike and foot off events, and to derive some temporo-spatial parameters, as well as some kinematic parameters.