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Hi,

Hope everything is going well with you.

In my research on children with cerebral palsy who suffer crouch gait or toe walking, I noticed that the values and weights in the IK Marker Task and IK Coordinate Task differ from those of the healthy group. Moreover, these values and weights significantly influence the final IK results. Do you have any suggestions on how to obtain more accurate data in studies of abnormal gait?

Best regards,
Xiaoxia

Hi Xiaoxia, this is probably a better question for the general OpenSim forum: indexPhpbb.php?group_id=91&pluginname=phpBB.

You could also consider applying for the Restore Center virtual office hours in the future: https://restore.stanford.edu/virtual-office-hours/

Hi Xiaoxia and Matt,

I thought I could help on this subject here since I will be starting a very similar project too.

As Matt said, in OpenSim, the IK relies on weights to "trust" the markers' data. More weight equals more "trust."

I regularly process mocap data (Vicon) with OpenSim. If the patient has impaired gait, I need to "trust less" in some markers.

This happens especially if the patient has valgus/varus foot. I hypothesize that the IK with the scaled model cannot cope with the markers of the foot (most of the time) when trusted equally. So, I usually decrease the weight of the foot markers when some odd things happen. I don't know if that's your case.

When the patient has severe foot deformities, if I leave all the weights equal, the IK usually converges to a gait with 180 degrees of hip rotation

Hope it helps.

Best regards.