joint moments from ID versus RRA

[John Rogers]

Hello,
I do not understand the output I am getting from Inverse Dynamics.
As an example, attached is a plot of hip_flexion_r_moment that I get from ID run on Sam Hamner's Subject 17 at 5 m/s.
It has a -5600 Nm dip at .35 seconds.
It looks nothing like the usual hip flexion moment.
Am I misunderstanding what I am looking at?
Thanks,
John

[jimmy d]

Hi John,

I ran ID on the model and speed that you used and got expected results (see attached, multiple strides).

Do you have any 'devices' attached to your model? springs, bushings, etc?

These may add unexpected forces into ID analysis. There is a 'do not include' list that can be added to ID. Internally we do this with muscle so that their force contributions are not seen.

Let us know if that helps,
-james

[John Rogers]

Thank you James,
I had soome error in the setup; likely an incorrect file. I started over and got good results.
See my ID (red) vs RRA (blue) results for Right Hip Flexion.
Regards,
John