Hi,
I want to validate a model by calculating joint forces by maximally
exciting muscles spanning the joint. Is it possible to do this in Anybody?
This will be an isometric task, so segment rotation is zero. Can I somehow
drive all msucles to their maximal activity and calculate joint reaction
force due to muscles? It seems like a forward dynamics problem, is there a
workaround for such problem in Anybody?
thanks for your help
prabhav
[Non-text portions of this message have been removed]
Hello Prabhaw,
AnyBody cannot do forward dynamics - sorry. But if you really want to do an
isometric task, i.e. fixed rotation of the segment, then it is not a forward
dynamics problem. You know the motion (or rather the position), which is the
same for all times.
As I read your email, you want to find the maximal joint moment the muscle
can produce. Is this right?
I that case, you can apply an external force to the leg that produce the
wanted joint moment, e.g. you can apply an AnyForce to the joint itself
(e.g. knee rotation would imply to apply a knee moment). If you then
increase this force (moment), e.g. as a function over time, you can identify
the point when the muscle activity becomes 1. This point is, in a modeling
sense, the maximal capability of the body. At this point you can read out
the value of the external load.
If you are looking to find other joint reactions, i.e., the constraint
reaction forces in the joint, then these will depend on the external force
you apply. But this is not your concern - is it?
Multi-degree of freedom joints and multi-articular muscles may make the
picture a bit more complicated. There are many parameters that may affect
the result you get, so the actual setup you make (posture and external
constraints supporting the body) are important; as they would be in a
laboratory experiment.
Also consider gravitational forces (not easy to get rid of in the
laboratory, but in AnyBody you can;-).
I hope this helps a bit.
Best regards,
Michael
Michael Damsgaard, AnyBody Support
<http://www.anybodytech.com> www.anybodytech.com
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Prabhav Saraswat
Sent: Wednesday, March 12, 2008 19:40
To: anyscript@yahoogroups.com
Subject: [AnyScript] Muscle Excitation
Hi,
I want to validate a model by calculating joint forces by maximally
exciting muscles spanning the joint. Is it possible to do this in Anybody?
This will be an isometric task, so segment rotation is zero. Can I somehow
drive all msucles to their maximal activity and calculate joint reaction
force due to muscles? It seems like a forward dynamics problem, is there a
workaround for such problem in Anybody?
thanks for your help
prabhav
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
Hi Michael,
Thats exactly what I was looking for. I am only
interested in maximal joint force all muscles spanning the joint can
produce. The method you described should solve the problem for me. i
will have only flexion/extension moment in the experimental set-up. So
there should be only one dof for the model. My only concern is that
all the muscle may not reach maximal activation together. I will keep
you posted on what i get out of the model.
Thanks for the quick reply.
Prabhav
On Mar 14, 2008, at 2:38 AM, AnyBody Support wrote:
> Hello Prabhaw,
>
> AnyBody cannot do forward dynamics - sorry. But if you really want
> to do an
> isometric task, i.e. fixed rotation of the segment, then it is not a
> forward
> dynamics problem. You know the motion (or rather the position),
> which is the
> same for all times.
>
> As I read your email, you want to find the maximal joint moment the
> muscle
> can produce. Is this right?
>
> I that case, you can apply an external force to the leg that produce
> the
> wanted joint moment, e.g. you can apply an AnyForce to the joint
> itself
> (e.g. knee rotation would imply to apply a knee moment). If you then
> increase this force (moment), e.g. as a function over time, you can
> identify
> the point when the muscle activity becomes 1. This point is, in a
> modeling
> sense, the maximal capability of the body. At this point you can
> read out
> the value of the external load.
>
> If you are looking to find other joint reactions, i.e., the constraint
> reaction forces in the joint, then these will depend on the external
> force
> you apply. But this is not your concern - is it?
>
> Multi-degree of freedom joints and multi-articular muscles may make
> the
> picture a bit more complicated. There are many parameters that may
> affect
> the result you get, so the actual setup you make (posture and external
> constraints supporting the body) are important; as they would be in a
> laboratory experiment.
>
> Also consider gravitational forces (not easy to get rid of in the
> laboratory, but in AnyBody you can;-).
>
> I hope this helps a bit.
>
> Best regards,
>
> Michael
>
> ------------------------------
>
> Michael Damsgaard, AnyBody Support
>
> <http://www.anybodytech.com> www.anybodytech.com
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
> On Behalf
> Of Prabhav Saraswat
> Sent: Wednesday, March 12, 2008 19:40
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Muscle Excitation
>
> Hi,
> I want to validate a model by calculating joint forces by maximally
> exciting muscles spanning the joint. Is it possible to do this in
> Anybody?
> This will be an isometric task, so segment rotation is zero. Can I
> somehow
> drive all msucles to their maximal activity and calculate joint
> reaction
> force due to muscles? It seems like a forward dynamics problem, is
> there a
> workaround for such problem in Anybody?
>
> thanks for your help
>
> prabhav
>
> [Non-text portions of this message have been removed]
>
> [Non-text portions of this message have been removed]
>
>
>
[Non-text portions of this message have been removed]
Hi Prabhav,
Just a brief comment.
Actually, you can be (almost) sure that not all muscles reach an activity of
1.0 simultaneously. For a certain loading situation, the muscles are needed
to various extend; even some are not needed at all, they will end with zero
activity, because they do not help carrying the load at all.
Using the “Min Max Muscle Activity” criterion, which is default in
AnyBodyStudy, you do however obtain that all muscle work together optimally
in the sense that the maximal activity cannot be lowered. This postpone the
point were any of the muscles reach activity of 1.0 as far as possible (i.e.
to as high load as possible) and it also implies that several muscles
(typically) reach 1.0 at the same time because to collaborate “optimally”.
Good luck with your investigation!
/Michael
Michael Damsgaard, AnyBody Support
<http://www.anybodytech.com> www.anybodytech.com
From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Prabhav Saraswat
Sent: Friday, March 14, 2008 16:51
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] Muscle Excitation
Hi Michael,
Thats exactly what I was looking for. I am only
interested in maximal joint force all muscles spanning the joint can
produce. The method you described should solve the problem for me. i
will have only flexion/extension moment in the experimental set-up. So
there should be only one dof for the model. My only concern is that
all the muscle may not reach maximal activation together. I will keep
you posted on what i get out of the model.
Thanks for the quick reply.
Prabhav
On Mar 14, 2008, at 2:38 AM, AnyBody Support wrote:
> Hello Prabhaw,
>
> AnyBody cannot do forward dynamics - sorry. But if you really want
> to do an
> isometric task, i.e. fixed rotation of the segment, then it is not a
> forward
> dynamics problem. You know the motion (or rather the position),
> which is the
> same for all times.
>
> As I read your email, you want to find the maximal joint moment the
> muscle
> can produce. Is this right?
>
> I that case, you can apply an external force to the leg that produce
> the
> wanted joint moment, e.g. you can apply an AnyForce to the joint
> itself
> (e.g. knee rotation would imply to apply a knee moment). If you then
> increase this force (moment), e.g. as a function over time, you can
> identify
> the point when the muscle activity becomes 1. This point is, in a
> modeling
> sense, the maximal capability of the body. At this point you can
> read out
> the value of the external load.
>
> If you are looking to find other joint reactions, i.e., the constraint
> reaction forces in the joint, then these will depend on the external
> force
> you apply. But this is not your concern - is it?
>
> Multi-degree of freedom joints and multi-articular muscles may make
> the
> picture a bit more complicated. There are many parameters that may
> affect
> the result you get, so the actual setup you make (posture and external
> constraints supporting the body) are important; as they would be in a
> laboratory experiment.
>
> Also consider gravitational forces (not easy to get rid of in the
> laboratory, but in AnyBody you can;-).
>
> I hope this helps a bit.
>
> Best regards,
>
> Michael
>
> ------------------------------
>
> Michael Damsgaard, AnyBody Support
>
> <http://www.anybodyt <http://www.anybodytech.com> ech.com>
www.anybodytech.com
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
[mailto:anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com]
> On Behalf
> Of Prabhav Saraswat
> Sent: Wednesday, March 12, 2008 19:40
> To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
> Subject: [AnyScript] Muscle Excitation
>
> Hi,
> I want to validate a model by calculating joint forces by maximally
> exciting muscles spanning the joint. Is it possible to do this in
> Anybody?
> This will be an isometric task, so segment rotation is zero. Can I
> somehow
> drive all msucles to their maximal activity and calculate joint
> reaction
> force due to muscles? It seems like a forward dynamics problem, is
> there a
> workaround for such problem in Anybody?
>
> thanks for your help
>
> prabhav
>
> [Non-text portions of this message have been removed]
>
> [Non-text portions of this message have been removed]
>
>
>
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]