RRA for Non-gait motions

[Mark Gordon]

I am simulating a leg press task. I am trying to get CMC to work but having a lot of issues. I was going to do RRA, but in the manual it says RRA is only intended for gait. Can I do RRA for my task (I do not have data for the forces on the seat, only from the foot)? If so, is that likely to help my CMC problems?

[Ayman Habib]

Hi Mark,

Unless you have full set of data to satisfy f=ma (within residual errors) it's not possible to get something useful out of either RRA, CMC or Forward. RRA for example tries to reduce "residuals" due to measurement errors, if you have other significant forces in the system that are not modeled that would definitely cause problems since they will be absorbed in these residuals. Running CMC later would be meaningless since the forces that the muscles will be asked to produce will have little connection to reality.

Good luck,
-Ayman

[Mark Gordon]

Can I get the forces from Inverse Dynamics? I have the foot force and the only other force would be gravity and the force of the subject on the chair of the leg press.

I believe Inverse Dynamics gives me a force on the pelvis to keep it in the correct location (basically stationary). If I add those forces to the pelvis would that be enough to run CMC?