In clinical gait trials for kinetic analysis involving one or more force plates, Vicon Nexus can automatically provide an indication of whether or not the foot is correctly positioned and is producing valid data for your live trials. Nexus displays this information on screen. This can save you time when you are assessing each foot strike to decide whether it is valid.
As each strike is detected, or is determined to be invalid, the box representing the force plate in the 3D Perspective view turns the appropriate color:
- Red: left foot strike
- Green: right foot strike
- Dark gray: invalid strike
Counters on either side of the force plate box show how many valid strikes have been detected for the left foot and the right foot during the current session.
To use auto-detection of foot strikes:
- Before you begin, ensure that you have:
- Calibrated the Vicon system.
- Applied the appropriate marker set to the subject.
- Ensured that you have a valid subject in Nexus.
- Connected and configured one or more force plates.
- On the Windows menu (or in the 3D Perspective view, right-click to access the context menu), click Footstrike Monitor Settings and in the dialog box, ensure the options for foot strikes are as required:
- Reset footstrikes button enables you to reset the foot strike counters.
- Force Threshold: Minimum force required on force plate to produce foot strike
- Marker Height Threshold: Minimum height of foot marker above force place for foot to be recognized for foot strike
- Left and Right Foot Markers: Comma-separated list of names of one or more markers that define the segment (i.e. foot) that will strike the plate.
- In the Options dialog box (press F7), ensure that Footstrikes is selected and that the display options for Font Size, Opacity, and Background Color are as required.
To reset foot strike counters:
- Right-click anywhere in the workspace and then click Reset.
- Press CTRL+SHIFT+R
Using multiple foot plates
If your trial requires multiple force plates, they are laid out in the order of the force plate IDs (that is, FP1 is furthest left/uppermost depending on the position of the force plate box).
Strikes straddling two force plates are marked invalid. However, if required they can be processed by the Process Dynamic Plug-in Gait Model pipeline operation, by selecting the Allow cross-plate strikes option.