How can I get out joint angles and loads from a model

[vikram chohan]

Hi,

So i have got my own data in which I have scaled the model in OpenSim and set up the inverse kinematics using the gait data i have obtained in a lab using markers. How do i get the joint angles and forces acting in this model?

Thanks in advance!

[Dimitar Stanev]

You have to perform an inverse kinematics and inverse dynamics analyses, respectively.

https://simtk-confluence.stanford.edu/d ... Kinematics
https://simtk-confluence.stanford.edu/d ... e+Dynamics

[vikram chohan]

So I have managed to do the inverse kinematics. However I am still struggling with the inverse dynamics. I have got an inverse dynamics file and all i want to find out are forces using opensim. Any further help you can give?

Thanks.

[Thomas Uchida]

Inverse Dynamics computes net joint moments. If you're interested in joint loads, you probably want to include the contribution of muscles.

[vikram chohan]

So is there no way to find out the overall force produced from one leg/foot?

[jimmy d]

Vikram, how can you estimate the joint and muscle forces produced when you don't have ground reaction forces?

[vikram chohan]

With respect to your answer of ground reaction forces, would that just not be x% multiplied by the body weight of the individual? So I need to find the weight of one muscle group(s) in order to get out a round reaction force?

[jimmy d]

Nope. Without some reaction force, you can't compute useful dynamics. If you want to just guess some forces to make a toy model and analyses, you can do that-- but it would just be that, a toy.

If you didn't collect any force data, there are public data sets that are available that have kinematic and force data. SimTK has walking and running projects.

[vikram chohan]

The force data I obtained via a mot file which was obtained from the gait lab and translated into opensim. No external forces/loads were applied.