Help with Scaling

[Filuta Ionescu]

I am using OpenSim to determine hip muscle forces for my study. Unfortunately, I don’t have any kind of experimental data. The only data I have for my model are the height and the weight of my specimen. My question is: how can I use these two pieces of information to determine a scaled model? Thank you

[Bryce Killen]

HI Filuta,

If you only have the height of your subject you have two options that spring to mind.

The first would be to use the height of your subject and the height of the model you want to scale a calculate a global scale factor and apply this to all bodies in your model. Not very elegant but still a solution which should ensure that your model is the same height as your subject

Alternatively there are plenty of anthropometry papers/studies which relate the height of an individual to the length of specific segments for example the femur. You could use these equations and calculate lengths of each body for your subject and then use the markers on the generic OpenSim model to calculate scaling factors for each body and apply those.

Hope this helps

Cheers
Bryce

[Thomas Uchida]

Good suggestions. I'll add another point: if you know only height and weight, you should probably be looking only for qualitative trends rather than detailed information about the individual muscle forces in your subject. To avoid potentially creating a model that is unlike any human, you might consider using a model that has already been scaled (e.g., for a subject whose height and weight are similar to those of your subject).

[Hela Rhouma]

Dear all,

I am working with the gait2392 model and I have the same problem.
I have only the age, height and weight of 12 subjects (female) and I have no idea how to scale the model. What equations to use to calculate scaling factors of each body segmets ?

Thank you

[jimmy d]

Hi, Hela-

Please read the Scaling section of the OpenSim Wiki. There is a section on defining scale factors.

[Muskan Agarwal]

Dear All,
I am also working with OpenSim for the first time and I have the same question. How do I scale my model if I have only the height, weight, foot size of my subject?
Please help