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Hi,

I am currently investigating whether using OpenSim to simulate a joint reaction analysis on an elbow is plausible. After countless attempts on using the analyze tool to obtain the joint reaction forces (JRF) on the elbow, I am still having doubt whether the results obtained are true since when i compared it with manual calculations, it yields totally different results. I am using the model of the Arm26 and interested in finding the JRF on the elbow joint when in a 90 degree elbow flex pose . Also, I realized that choosing different set of frames and forces to apply to yields a different result and I have some trouble understanding on which parent or child frame to choose.

I have also been suggested to stripped down all the muscles on the model and calculate the joint reaction at the elbow. By doing this, I managed to obtain almost true to the result when comparing it with manual calculation. However, when I proceed to add the BIClong muscle, I obtained two very distinguishable results when comparing with manual calculation. I am confident that the calculations I did manually is fairly accurate but the results does not reflect that.

Attached is the rough calculation of both with and without the BIClong muscle

Any help would be gladly appreciated, Thank you!

The webinar and example files on the "Example - Estimating Joint Reaction Loads" page in the Confluence documentation (https://simtk-confluence.stanford.edu/d ... tion+Loads) might be helpful.

Thank you,

The methods that I used are all based on the webinar video however I am not particularly sure if my calculations are accurate since in the webinar, they have actuators and external data force which I do not have it in my calculation.