Pulling in-motion muscle-tendon lengths out

[Daniel Leib]

Good morning,

I've recently been very interested in using OpenSim to generate muscle-tendon lengths during dynamic activities such as walking and cycling, and I think I may have stumbled on a way to do it. Since I don't really have anything to compare the numbers to, however, I thought it best to make sure I'm not simply generating a data set that happens to look like, but isn't really, muscle lengths.

After running the RRA analysis, if you go to the plot tool and put muscle-tendon length on the Y axis and choose a muscle, it is possible to plot the resulting RRA_states file on the X axis. It appears to then generate the muscle length plotted against time from the simulation.

Is this supposed to happen? Is it actually muscle length being plotted? The values seem reasonable given the tasks and subjects I've tried it on.

Thanks,

Dan

[Ayman Habib]

Hi Dan,

That's indeed the case. You can plot muscle lengths (and all other buit-in quantities) during a motion by picking the motion/time for X quantity, muscle-length for Y and the muscle(s) you care about for muscle-names.

We will release a User's guide that will detail all this very soon.

Good luck,
-Ayman

[Daniel Leib]

Ah, fantastic! This will be very helpful in my thesis!

Thanks,

Dan