sit-to-stand, can one GRF be split and applied to each foot?

[Karen Fitzgerald]

Hi all,

I have gait data for a sit-to-stand trial however both of the subject feet are on one force plate.
When I create my .mot file for this grf I have a force applied somewhere between both feet which makes sense (see image attached).

I was wondering is there a way to split this force between both feet as it should essentially be half the force for each foot. I know it wont be an exact solution but I can't remeasure this subject with a foot on two separate force plates.

Has anybody had any experience with this?
I would love to hear your suggestions/advice.

Thanks,
Karen

Screenshot 2018-11-19 11.52.08.png (106.76 KiB) Viewed 218 times

[jimmy d]

I was wondering is there a way to split this force between both feet as it should essentially be half the force for each foot. I know it wont be an exact solution but I can't remeasure this subject with a foot on two separate force plates.

Using a tool of your choice (Matlab, Python, Excel), you could divide the GRF into two forces (XYZ components) that have no moments. To calculate a location to apply these forces, you could report the location of markers placed on the (approximate) underfoot surface of both feet.

Using these assumptions, you would limit yourself in some ways (no moments), but you are limited by your data anyway.

[Karen Fitzgerald]

Thanks for the advice James.

I'll give this a try.