Collect synchronized EMG and GRFs

[Arian Vistamehr]

Is there a way to collect synchronized experimental EMGs and GRFs? What hardware/software is needed to synchronize the data with OpenCap videos?

[Scott Uhlrich]

There is no way to hardware sync with OpenCap, as everything is done over internet.

We do have an example of using common signals to synchronize a force plate (https://github.com/stanfordnmbl/opencap ... ntegration). Keep in mind, however, the time sync'ing method is specific to the task (jumping in this example). If you have marker-based mocap, you could also time synchronize using marker data (e.g. put a marker on the pelvis or hand).

Another approach some people use is to have an LED that signifies when the analog data (GRFs, EMG) start and stop collecting, and visualize the light in the sync'd opencap videos.

[Arian Vistamehr]

Thanks, Scott. Could you please re-send the link again? It does not work.

Is there a way to save the GRFs and video-based marker data in a c3d file for further analysis? Otherwise, how would you suggest integrating GRF data for inverse dynamics analysis? Do you recommend using OpenCap solely for kinematics analysis at this point?

[Scott Uhlrich]

https://github.com/stanfordnmbl/opencap ... ntegration

We do not currently write out to c3d. You can see how we do inverse dynamics in this example. It is possible to do inverse dynamics, but the synchronization part is non-trivial.