"GaitLowExtremity" model

[LEFT][FONT=Arial]Hi, [/FONT][/LEFT]

[LEFT][FONT=Arial]I have questions.[/FONT][/LEFT]

[LEFT][FONT=Arial]I’m using GaitLowExtremity model and I did experiments 23 markers(RFHA,LFHD,LBHD,RBHD,T10,RASI,LASI,LPSI,RPSI,PTHI,LTHI,RKNE,LKNE,RTIB,LTIB,RANK,LANK,RTOE,LTOE,RHEE,LHEE,RMT5,LMT5) & 2 force plates. [/FONT]
[FONT=Arial]And my c3d file is imported in model. (and I performed optimization model and inverse dynamics model)[/FONT][/LEFT]

<First Q>

[LEFT][FONT=Arial]In general, during mid-stance(phase of gait cycle), triceps surae(especially gastrocnemius) are active.[/FONT]
[FONT=Arial]But gastrocnemius’s muscle force and activity of my c3d file were shown very very small values. [/FONT]
[FONT=Arial]Is there something(experimental condition: marker set location or number) wrong??[/FONT][/LEFT]

<Second Q>
And, I’m trying to operate(inverse dynamics) with just a few muscles in GaitLowExtremity model.
Please tell me what to do.

Thank you.


It is difficult to tell exactly why you do not see much activity in the gastrocnemius muscle for the mid-stance, it can many things.

Usually the first thing to look at would be the joint moments, these can be found in the selected output folder, of the human model. Please evaluate these and ensure they look plausible.

Concerning the second question the easiest way to exclude muscles from the model is to use the MechObjectExclude facility of the AnyBodyStudy, in this way you can exclude the muscle from being active mechanically in the study without removing for real…

Please look up the AnyBodyStudy in the reference manual and see the sample code provided which shows how the MechObjectExclude works (scroll to bottom of page)

Be careful when you exclude the muscles you may end up with a model which can not balance the forces.

Best regards

I attached .zip file.
The .pdf file is based on the whole contents of what I’ve been doing and about my first question.
And my data(c3d file, AnyBody file) is included.

Think about it, then let me know.

Best regards.


The problem is that the force plates are upside-down in your model. So of course the force is not applied correctly and the muscle activity is unrealistic.

However i am not sure why those plates are upside-down. They get their orientations from the CORNERS data of the C3D file. I checked on C3D.org and the plates are correctly oriented regarding to the corners, so i suspect that it is the corners themselves that are incorrect. If you switch the corner 1 with the 4 and the 2 with the 3 in ForcePlateType4AutoDetection.any it will look right.

I can’t say what is the reason for this corner problem. Maybe something went wrong in your experimental setup.

Best regards, Sylvain.

So, could I changed it the same force plate formats of AnyBody example model??
For example, using C3D editor program, force plate’s origin and corners and cal matrix…


I think it would be good to investigate why the corners are switched around in the file, to avoid having the problem another time.

Right now you don’t need to have the exact same plate setup as the repository application, but just to get the plates facing up and not down. So i think changing the order of the corners in a C3D editor program will fix it for the moment. Anyway i still recomend to find the real cause of it.

Best regards, Sylvain.