What is a unit of muscle activation in OpenSim?

[Hyun-Seob, Lee]

Hi everyone.
I have a few questions about muscle activation value while studying OpenSim.
I had the following figure which is made in OpenSim. In the figure, muscle activation values are showed on the Y-axis.
그림1.png

1. Are this values normalized? If then, how is normalizing?
2. What is mean these muscle activation values?
3. What are differences compare with EMG activation signal?


I have been searching the information about activation unit in OpenSim. But I can't find it.


Please let me know any information!


Thanks,

[Aaron Fox]

Re: What is a unit of muscle activation in OpenSim?

Hi Lee,

I believe you can view these activation values much like you would a normalised EMG signal, with a value of 1 representing the maximal activation achievable by the muscle. The activation used by the muscle in OpenSim is dictated by things like it's maximum force, current fibre length, optimal fibre length, pennation angle, current contraction velocity etc., much like a normal physiological muscle is. I believe in most studies people compare these activation values from OpenSim to their EMG signals normalised to maximal voluntary contractions or similar.

Hope that helps,

Aaron

[Hyun-Seob, Lee]

Re: What is a unit of muscle activation in OpenSim?

Thanks for your response with explaining.
Your post helped me a lot really.

If you have any related documents or webpage, please let me know.

Have a nice day.

Lee

[Hyun-Seob, Lee]

Re: What is a unit of muscle activation in OpenSim?

Thanks for your response with explaining.
Your post helped me a lot really.

If you have any related documents or webpage, please let me know.

Have a nice day.

Lee

Hi Lee,

I believe you can view these activation values much like you would a normalised EMG signal, with a value of 1 representing the maximal activation achievable by the muscle. The activation used by the muscle in OpenSim is dictated by things like it's maximum force, current fibre length, optimal fibre length, pennation angle, current contraction velocity etc., much like a normal physiological muscle is. I believe in most studies people compare these activation values from OpenSim to their EMG signals normalised to maximal voluntary contractions or similar.

Hope that helps,

Aaron

[Manvendra Singh]

Re: What is a unit of muscle activation in OpenSim?

Check https://simtk-confluence.stanford.ed...ation+Dynamics

[Hyun-Seob, Lee]

Re: What is a unit of muscle activation in OpenSim?

Thanks Manvendra.