Welcome to the group
I have tried to answer your questions below
— In firstname.lastname@example.org, “yocollet” <yoann.collet.1@e…>
> My name is Yoann and i’m working on a project for my master degree.
> I’m from the french Alps near Evian and i’m in Montreal for a
> A part of my project is the modeling if the human shoulder. I will
> use Anybody for this.
> I’ve just got a problem to solve before the modeling.
> How could I define the line of action of the deltoid during
> elevation, in a 2D way first?
I am not sure i understand what is it you would like to do. Normally
we control the muscle line of action by its origin and insertation
points. The muscle may also wrap around spheres and cylinders, its
all in 3D. I am not sure what it is you would like to do in 2D?
> Litterature give the values, but can we define it only by the view
> of the bones?
By line of action do you mean moment arm and is it these values you
have from the literature?
It is not possible to type in directly what should the moment arm
variation for a specific muscle when the arm is elevated. What you
can do is to use the geometry of the bones that the muscle should
wrap around, and then define a AnyShortestPathMuscle which finds the
shortest path from origin to insertation. You may then change the
geometry that the muscle wraps around and it’s insertation and
origin points, until you have the desired moment arm variation.
PCSA of the deltoid is just known for a passive muscle
> or in one position.
The value of the PCSA will not change the line of action or the
momentarm in our model. The muscles are modelled geometrically as
strings with no thickness.
> A solution should be to fix a line from the center of insertion on
> the humerus to the “middle-thickness” of the muscle.
> We know moment arm of deltoid muscle is not constant and not
> during elevation, so it’s quite difficult.
> May you help me?
If you would like that the size of PCSA should have an effect on the
moment arm, it can be done by increasing the size of the geometry
that the muscle wraps around. If you use the AnyShortestPathMuscle
and your geometry is correct in terms of insertation origin and
wrapping surfaces, you should end up with a correct nonlinear
variation of the moment arm.
Please do not hesitate to ask again if you have further questions
> Thank you