RRA time duration

[Quinten Humphrey]

For executing RRA, I have gathered that the time duration should be when the model is about to step onto the force plate until it steps off. My model stands on the force plates throughout the whole task. Would it be more beneficial to make the time duration smaller or is it fine as it is?

[Carmichael Ong]

For executing RRA, I have gathered that the time duration should be when the model is about to step onto the force plate until it steps off

While this is correct for many cases, I'd like to tighten up the use case a little bit. You should be careful to use RRA only during times when you have all external forces accounted for, or else there will be a mismatch in the external forces applied to the model and the kinematics from the marker data. So, often this comes up in walking where you have to be careful about this in double support phase if one foot is on a force plate and the other is not. While in running, even though there are times where neither foot is on a force plate, but that's ok because neither foot is on the ground!

Would it be more beneficial to make the time duration smaller or is it fine as it is?

This may depend on your exact research question. Do you need to analyze the whole time on the force plate to get to the outcome measures you were looking to calculate? Will you use CMC afterwards (which means you'll be missing the first 30ms at the start of the simulation as the muscles equilibrate) or static optimization (which does not need any time to equilibrate and is a frame-by-frame method)?

[Quinten Humphrey]

Thank you for your help.

For more clarity, my model is based on a pick and place task where both of the subject's feet are standing on their respective force plate for the whole duration (~8.6 seconds) so there is no actual running or walking over the plate. As in this case, I believe the external forces match the IK data.