Modifying passive force-length curve properties of DeGrooteFregly2016Muscle

[Karthick Ganesan]

Hi all,
How can I modify the passive FL curve properties of this muscle. I can modify the passive fiber strain at one norm force . What about the other properties?
Thanks,
Karthick.

[Nicholas Bianco]

Hi Karthick,

Currently, passive fiber strain at one norm force is the only property that's modifiable on the DGF muscle. What are you trying to change? Perhaps we'll add other properties to control the passive force curve in the future.

-Nick

[Karthick Ganesan]

Thanks Nick.
As Ross pointed out that in his model rectus femoris produces high passive force in the beginning of swing phase, I wanted to tweak some passive force properties. Passive strain at one norm force is already set as 1 compared to the default 0.6. So thought of changing curviness or exponential shape factor.

Karthick.

[Nicholas Bianco]

The passive strain parameter usually has the largest effect on passive force, hence why it is a property of the model. You might find that you need to increase the passive strain well above the default to avoid excessive forces, especially in biarticular muscles like the recfem, which undergo large excursions.