Muscle activity as defined by AnyBody is literally when a muscle is
active, right? It says in the documentation that MuscleActivity is
the normalized muscle force, and I just wanted to be clear that the
muscle activity is what I think it is.
Hi Sarah
The muscle activity is defined as f/N, here f is the muscle force
and N is the muscle strength, there is no activation dynamics
involved, so the activity reflects the current force in the muscle
normalized with the muscles current strength.
Best regards
Soeren AnyBody Support
— In anyscript@yahoogroups.com, “Sarah R. Sullivan”
<sarsulli@e…> wrote:
>
> Muscle activity as defined by AnyBody is literally when a muscle is
> active, right? It says in the documentation that MuscleActivity is
> the normalized muscle force, and I just wanted to be clear that the
> muscle activity is what I think it is.
>
Hi,
I have questions about muscle activity data output. Is the muscle activity
defined by dividing
Fm by Strength? If it is correct, I assume that the activity value should always
lower than one.
I am wondering why there are several muscles in my models have the activity
value output
more than one? A file named MVC.zip has been uploaded for your reference. This
model is
used to simulate a MVC test of knee extension in sitting position. A force is
loaded on the
ankle joint similar to the subject test.
I would like to use these subject MVC test simulations to determine individual
subject’s
muscle strength. I am wondering is there any good way to scale the muscle
strength in the
AnyBody?
Thanks in advance for your answer.
Mark
Hi Mark,
It is exact that the muscle activity is defined by dividing the
muscle force by his strength. So the muscle activity should be always
lower than one in real human body. However in AnyBody the muscles can
provide a force higher than their own strength and therefore have an
activation of more than 100%. When this occur you can see the
concerned muscle become purple in the view window, and that mean a
normal person should not be able to do this particular movement.
In your case the over activity is very high (1300%) so I suspect some
problems in the boundary conditions. The drivers for the body look
good, I actually have a doubt on the load applied on the ankles. 500
N in each leg sounds a lot to me, in addition that it is applied in
backward in a direction where the leg are not so strong. My idea is
that you should check if the load is correct.
You can scale the muscle strength in two ways. There is this line in
the Main file:
AnyVar StrengthIndexLeg= 1;
This variable is a global strength factor for all the leg’s muscles.
If you want to scale each muscle individually then you have to do it
in the BRep/Aalborg/Leg3D/MusPar.any file where you will find the
muscle model for each muscle.
Best regards,
Sylvain, AnyBody Support.
— In anyscript@yahoogroups.com, “chiayuan1116” <chiayuan1116@…>
wrote:
>
> Hi,
>
> I have questions about muscle activity data output. Is the muscle
activity defined by dividing
> Fm by Strength? If it is correct, I assume that the activity value
should always lower than one.
> I am wondering why there are several muscles in my models have the
activity value output
> more than one? A file named MVC.zip has been uploaded for your
reference. This model is
> used to simulate a MVC test of knee extension in sitting position.
A force is loaded on the
> ankle joint similar to the subject test.
>
> I would like to use these subject MVC test simulations to determine
individual subject’s
> muscle strength. I am wondering is there any good way to scale the
muscle strength in the
> AnyBody?
>
> Thanks in advance for your answer.
>
> Mark
>