meaning of axes in the tendon force length curve

[Linjie Wang]

Hi, there.

Could anyone help explain what the X and Y axes in the tendon force length curve mean and their units? I read from some literature that Y means the normalized force (tendon force by optimal force) and X means the strain ((tendon length-tendon slack length)/tendon slack length). However, in light of the values in the screenshot, I am quite suspicious that is not the case at all, at least for this type of muscle (Schutte).

Thanks,
Linjie

[jimmy d]

The Schutte muscles are deprecated and are no longer supported. I am not sure why you would be using them.

The source code for the (deprecated) Shutte muscle muscle is here. The specific curve is hardcoded from line 79.

The normalized Tendon length is calculated, and strain is used as the input to the (hardcoded) spline. So it seems that the X-axis is strain and the Y-axis is force.

[Linjie Wang]

Hi, James.

Thanks a lot for your reply.

I downloaded the model from Grand challenge competition to predict in vivo knee loads. And the muscles in that model are the Schutte type. I noticed Ayman used to explain in one post that although Schutte muscle has been deprecated, it still works. Deprecation only means this muscle type has been stopped for further development and test.

Anyway, so do you suggest to use latest muscle type such as Millard?

Thanks again,
Linjie

[jimmy d]

yep.

[Linjie Wang]

Thanks!

[Linjie Wang]

Ive changed the muscle into the Millard equilibrium type. However, when I run CMC again, the calculation even failed at the states calculatioin. No matter how I increased the control values, or changed some mucsles' max isometric force, optimal fiber length, tendon slack length, the calculatioin just couldn't go beyond. Does anyone know the possible reasons? Any suggestion would be appreciated.

Thanks in advace,
Linjie