Hello to everybody,
I have a simple question.
Is it possible to get the direction of muscle forces in deformed and
undeformed configuration?
with best regards.
Natiq
Hi Natiq
I am not sure, i fully understand the question, what do you mean by deform
and un deformed configuration?
It is possible to use the AnyForceMomentMeasure to find the direction and
magnitude of a muscles force where it attaches to the bone.
In the file section of this group there is a small example of this issue.
Please see the file SmallExamples/OutputForFE.any (or something very
similar ;-)), it should explain among other things how this is done.
Best regards
Søren
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of natiqpervaiz
Sent: 22 February 2008 11:21
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle forces
Hello to everybody,
I have a simple question.
Is it possible to get the direction of muscle forces in deformed and
undeformed configuration?
with best regards.
Natiq
[Non-text portions of this message have been removed]
Hello,
Thanks for the reply from my previous post as to why the inverse
dynamics did not work. The model works fine now.
However, I have one problem regarding the muscle forces calculated.
Only the muscles which are in contraction appear to exert any force,
with all other muscles remaining passive. For example, the gluteus
maximus is expected to be active, but is not. I wondered - is this
down to poor muscle definition or other factors of the model (e.g.
moment of inertia’s are set to zero). Although the model only performs
a simple motion, I think the extending muscles should still have some
force (similar to the arm model in the tutorial). Also, the calculation
of the muscle length appears to change when all muscles are modelled
together, compared to when they are modelled individually, even though
the same motion is performed.
I have uploaded the model (HipJoint) and would be grateful of any
advice you may be able to provide.
Many Thanks
Hi,
I think the first reason why you don’t get reasonable activations is because
the units in your model are not coherent. AnyBody don’t work with a specific
unit system, however the system used have to be coherent. We usually use the
SI units. In your model the forces are still in N and the gravity in m.s-2
as usual but the segments dimensions are in centimetres instead of meters as
they should.
So I think the first step is to adjust the units in a coherent system.
Also it would be better to give some moment of inertia to the bones.
About the muscle length you are right there is a small bug but it is
actually of no importance for the results. The output variable Lmt is the
length of the total muscle-tendon unit and Lm is the length of the
contractile element only. In the case of the simple muscle model those two
variables have the same value because the muscle is only a contractile
element. The bug is the following: sometimes Lm returns the value of another
muscle of the model, but Lmt is always correct and is the one you should be
looking at.
Notice that this happens only with the simple muscle model where neither Lm
nor Lmt are used for other calculations, therefore there is no impact on the
muscle forces.
Best regards,
Sylvain, AnyBody Support
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of dc_pete
Sent: 15. januar 2009 16:01
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle Forces
Hello,
Thanks for the reply from my previous post as to why the inverse
dynamics did not work. The model works fine now.
However, I have one problem regarding the muscle forces calculated.
Only the muscles which are in contraction appear to exert any force,
with all other muscles remaining passive. For example, the gluteus
maximus is expected to be active, but is not. I wondered - is this
down to poor muscle definition or other factors of the model (e.g.
moment of inertia’s are set to zero). Although the model only performs
a simple motion, I think the extending muscles should still have some
force (similar to the arm model in the tutorial). Also, the calculation
of the muscle length appears to change when all muscles are modelled
together, compared to when they are modelled individually, even though
the same motion is performed.
I have uploaded the model (HipJoint) and would be grateful of any
advice you may be able to provide.
Many Thanks
[Non-text portions of this message have been removed]
Thanks for the advice, much appreciated.
— In anyscript@yahoogroups.com, AnyScript Support
<anyscriptsup@…> wrote:
>
> Hi,
>
>
>
> I think the first reason why you don’t get reasonable activations
is because
> the units in your model are not coherent. AnyBody don’t work with a
specific
> unit system, however the system used have to be coherent. We
usually use the
> SI units. In your model the forces are still in N and the gravity
in m.s-2
> as usual but the segments dimensions are in centimetres instead of
meters as
> they should.
>
> So I think the first step is to adjust the units in a coherent
system.
>
> Also it would be better to give some moment of inertia to the bones.
>
>
>
> About the muscle length you are right there is a small bug but it is
> actually of no importance for the results. The output variable Lmt
is the
> length of the total muscle-tendon unit and Lm is the length of the
> contractile element only. In the case of the simple muscle model
those two
> variables have the same value because the muscle is only a
contractile
> element. The bug is the following: sometimes Lm returns the value
of another
> muscle of the model, but Lmt is always correct and is the one you
should be
> looking at.
>
> Notice that this happens only with the simple muscle model where
neither Lm
> nor Lmt are used for other calculations, therefore there is no
impact on the
> muscle forces.
>
>
>
> Best regards,
>
> Sylvain, AnyBody Support
>
>
>
>
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of dc_pete
> Sent: 15. januar 2009 16:01
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Muscle Forces
>
>
>
> Hello,
> Thanks for the reply from my previous post as to why the inverse
> dynamics did not work. The model works fine now.
> However, I have one problem regarding the muscle forces calculated.
> Only the muscles which are in contraction appear to exert any
force,
> with all other muscles remaining passive. For example, the gluteus
> maximus is expected to be active, but is not. I wondered - is this
> down to poor muscle definition or other factors of the model (e.g.
> moment of inertia’s are set to zero). Although the model only
performs
> a simple motion, I think the extending muscles should still have
some
> force (similar to the arm model in the tutorial). Also, the
calculation
> of the muscle length appears to change when all muscles are
modelled
> together, compared to when they are modelled individually, even
though
> the same motion is performed.
> I have uploaded the model (HipJoint) and would be grateful of any
> advice you may be able to provide.
> Many Thanks
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
Hi,
so far I’ve used the simple muscle model (BodyModel) to calculate the
muscle forces and use them in FEM software. Therefore I’ve used the Fm
value as it represents the total muscle force.
But if I use the MuscleModel3E what is my total muscle force which I
have to consider on the bone in FEM?
Fm is for the contractile element, Fp for the passive force and Ft the
tendon force.
Do I have to sum up this three values to become the total muscle force?
Thank you.
Best regards
Thomas
Hi Thomas
When using the three element muscles model, then simply use the tendon force
Ft, as the input for the FEM model, this is the force the acting on the
bone.
Best regards
Søren, AnyBody Support
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of knox40
Sent: 29 January 2009 09:48
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle Forces
Hi,
so far I’ve used the simple muscle model (BodyModel) to calculate the
muscle forces and use them in FEM software. Therefore I’ve used the Fm
value as it represents the total muscle force.
But if I use the MuscleModel3E what is my total muscle force which I
have to consider on the bone in FEM?
Fm is for the contractile element, Fp for the passive force and Ft the
tendon force.
Do I have to sum up this three values to become the total muscle force?
Thank you.
Best regards
Thomas
[Non-text portions of this message have been removed]