Muscle reaches 100% activation in walking and don't why - SO and RRA

[Israel Luis]

Dear Community,

I am doing a standard simulation of walking with OPENSIM 4.0: experimental data obtained from VICON and force plate. I did all the tutorials but I feel very frustrated because Med Gasctronemuis reaches more than 100% activation in Static optimization (after RRA which fulfills the OpenSim recommendations) and I do not why. I have tried many parameters for days: RRA Task, RRA actuators and SO actuators, but I cannot get the muscle activation to get down. I can only achieve it if I increase the SO additional actuators quite high (around 20 Nm) but I have read that these are usually relatively low (<1 Nm).

Could someone suggest to me what could be wrong, please? (I attach the graphs of moments ID and RRA, residuals and MedGas activation)

[Michael Asmussen]

Hi,

Which model are you using for the static optimization? Also, what speed were the participants walking at? Do you have any EMG data to compare your activations against?

All the best,

Mike

[D T]

I am currently going through the same issue. I am unsure if this is a product of the specific model, or if certain inconsistencies in markers cause muscle activities to spike.

[Martin Hora]

Check what model you are using. Old models like gait2392_simbody.osim had low maximum isometric force (e.g., soleus 3549 N) - I had to multiple the max_isometric_force values of plantarflexors by two to get muscle activations during walking below 100%. Newer models like Rajagopal2015.osim have much stronger plantarflexors (e.g., soleus 6194 N).

Best
Martin

[ZHONG WEI]

Hello,friends
Have you solved the problem yet? I am currently going through the same issue and I use Rajagopal2015.osim. Are there criteria for modify if need to change max_isometric_force values?
Best regards!
WEI