Joint Reaction Force

Archive AnyScript Yahoo archive
1

Hi,

I facing a problem with my model. May I know what does the joint
reaction force actually measure? When I did a single right leg drop
landing model, the peak knee reaction force is about 18800N which is
very large. It is about 40 time body weight. Why is the reading so
large? Is it due to the absolute joint reaction force experience by the
knee due to the muscle? pls advise.

Thanks

Best Regards
Eugene

2

Hello Eugene,

This post might be of interest to you.

http://tech.groups.yahoo.com/group/anyscript/message/1192

Cya,

Jean-Olivier

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of eugeneyang40
Sent: Thursday, August 02, 2007 12:13 PM
To: anyscript@yahoogroups.com
Subject: [AnyScript] Joint Reaction Force
Importance: High

Hi,

I facing a problem with my model. May I know what does the joint
reaction force actually measure? When I did a single right leg drop
landing model, the peak knee reaction force is about 18800N which is
very large. It is about 40 time body weight. Why is the reading so
large? Is it due to the absolute joint reaction force experience by the
knee due to the muscle? pls advise.

Thanks

Best Regards
Eugene

[Non-text portions of this message have been removed]

3

Hi Jean-olivier

Thanks for the link.

I roughly understand the reason behind model with and without muscle.
But I am still puzzled by the large force generated. I used the
following and obtain my kneereaction from the ChartFX under
KneeReaction/F:

AnyForceMomentMeasure KneeReaction = {
AnyRefFrame &Ref = .SegmentFolder.Shank.KneeJoint;
AnyRefFrame &Reac = .JointFolder.Knee.Constraints.Reaction; };

The reading is different from Fout under the constraint. Why is that
so? Which should be the value for me to use. I had uploaded a model
in yahoogroup under single leg landing folder. Does the value
reflects the actual knee reaction force experience by the subject or
it simply due to the muscle acting on it. Sorry, I am really lost
with this and need to write a report on this. Pls help.

Thank you

Regards
Eugene

— In anyscript@yahoogroups.com, Jean-Olivier Racine <jean-
olivier.racine.1@…> wrote:
>
> Hello Eugene,
>
>
>
> This post might be of interest to you.
>
> http://tech.groups.yahoo.com/group/anyscript/message/1192
>
>
>
> Cya,
>
> Jean-Olivier
>
>
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of eugeneyang40
> Sent: Thursday, August 02, 2007 12:13 PM
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Joint Reaction Force
> Importance: High
>
>
>
> Hi,
>
> I facing a problem with my model. May I know what does the joint
> reaction force actually measure? When I did a single right leg drop
> landing model, the peak knee reaction force is about 18800N which
is
> very large. It is about 40 time body weight. Why is the reading so
> large? Is it due to the absolute joint reaction force experience by
the
> knee due to the muscle? pls advise.
>
> Thanks
>
> Best Regards
> Eugene
>
>
>
>
>
> [Non-text portions of this message have been removed]
>

4

Hi Eugene

I have been investigating your model a bit.

I have tried to run the model named MyLanding2LV2.zip

If you run this model without the muscles on you will get a reaction
in the hip joint in the z direction starting from 2900N and then
dropping to about 650N. This is in correspondance with the input
force on the forceplates, which looks identical.

The reason why the AnyForeMomentMeasure displays a different value
then the fout of the joint is a difference in the reference
cooridnate system. When applying the AnyForceMomentMeasure it wil
measure in the global ref system whereas the fout of the knee joint
are using the references of the shank knee joint node as i recall
it.

If you then apply the muscles to the model you should expect higher
forces because the muscle contractions will increase the reaction
forces of the joint. These reaction forces are the real onces that
the subject will “feel”. These force are a combination of the load
applied in the force plates and the reaction forces the muscles
generates on the knee, this is like in reality.

That said the reaction force seems rather high, but i am not sure
what a realistic level is for this exercise. If you look at your
muscle activities these are also rather high and indicates that the
model is overloaded.

I hope this explanation made things more clear otherwise please
write again.

Best regards
Søren, AnyBody Support

— In anyscript@yahoogroups.com, “eugeneyang40” <eugeneyang40@…>
wrote:
>
> Hi Jean-olivier
>
> Thanks for the link.
>
> I roughly understand the reason behind model with and without
muscle.
> But I am still puzzled by the large force generated. I used the
> following and obtain my kneereaction from the ChartFX under
> KneeReaction/F:
>
> AnyForceMomentMeasure KneeReaction = {
> AnyRefFrame &Ref = .SegmentFolder.Shank.KneeJoint;
> AnyRefFrame &Reac = .JointFolder.Knee.Constraints.Reaction; };
>
> The reading is different from Fout under the constraint. Why is
that
> so? Which should be the value for me to use. I had uploaded a
model
> in yahoogroup under single leg landing folder. Does the value
> reflects the actual knee reaction force experience by the subject
or
> it simply due to the muscle acting on it. Sorry, I am really lost
> with this and need to write a report on this. Pls help.
>
> Thank you
>
> Regards
> Eugene
>
>
> — In anyscript@yahoogroups.com, Jean-Olivier Racine <jean-
> olivier.racine.1@> wrote:
> >
> > Hello Eugene,
> >
> >
> >
> > This post might be of interest to you.
> >
> > http://tech.groups.yahoo.com/group/anyscript/message/1192
> >
> >
> >
> > Cya,
> >
> > Jean-Olivier
> >
> >
> >
> > From: anyscript@yahoogroups.com
[mailto:anyscript@yahoogroups.com]
> On Behalf
> > Of eugeneyang40
> > Sent: Thursday, August 02, 2007 12:13 PM
> > To: anyscript@yahoogroups.com
> > Subject: [AnyScript] Joint Reaction Force
> > Importance: High
> >
> >
> >
> > Hi,
> >
> > I facing a problem with my model. May I know what does the joint
> > reaction force actually measure? When I did a single right leg
drop
> > landing model, the peak knee reaction force is about 18800N
which
> is
> > very large. It is about 40 time body weight. Why is the reading
so
> > large? Is it due to the absolute joint reaction force experience
by
> the
> > knee due to the muscle? pls advise.
> >
> > Thanks
> >
> > Best Regards
> > Eugene
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>

5

Hi Soren,

I am facing a few problems here and really not sure how to solve it.
I have uploaded 3 new model (all right leg only) in the landing gait
folder.

  1. The first model is base on a small hop and landing on single
    leg.The hop is only very small, basically like a step forward and
    then land on single leg and finish off with a single leg squat. The
    joint reaction force (JRF) at knee is about 9000N. The second model
    is the full movement recording at 200Hz. For this model, it i run it
    at nStep = 101, i get a peak force of about 13000N, and at nStep=
    step, the peak JRF is 24000N.(Which result will be reasonable to
    use?) The third model also the full movement but recording at 400Hz.
    This one i get a peak force of 33000N.

2)Therefore, is there anything wrong about my modeling that resulted
in such huge Knee JRF? Can i model a landing like this?

  1. Since Anybody is an optimisation software, how much is the result
    overestimated. Can I assume about double?

Since a squat is about 5 to 6 times body weigh, assuming if single
leg is about 12 times BW, the small hop should not reach 20 times BW.

Thank you. I hope my question is not to confusing. Do hope anyone who
is familiar with this can help.

Best Regards
Eugene

– In anyscript@yahoogroups.com, “AnyBody Support” <support@…>
wrote:
>
> Hi Eugene
>
> I have been investigating your model a bit.
>
> I have tried to run the model named MyLanding2LV2.zip
>
> If you run this model without the muscles on you will get a
reaction
> in the hip joint in the z direction starting from 2900N and then
> dropping to about 650N. This is in correspondance with the input
> force on the forceplates, which looks identical.
>
> The reason why the AnyForeMomentMeasure displays a different value
> then the fout of the joint is a difference in the reference
> cooridnate system. When applying the AnyForceMomentMeasure it wil
> measure in the global ref system whereas the fout of the knee joint
> are using the references of the shank knee joint node as i recall
> it.
>
>
> If you then apply the muscles to the model you should expect higher
> forces because the muscle contractions will increase the reaction
> forces of the joint. These reaction forces are the real onces that
> the subject will “feel”. These force are a combination of the load
> applied in the force plates and the reaction forces the muscles
> generates on the knee, this is like in reality.
>
> That said the reaction force seems rather high, but i am not sure
> what a realistic level is for this exercise. If you look at your
> muscle activities these are also rather high and indicates that the
> model is overloaded.
>
> I hope this explanation made things more clear otherwise please
> write again.
>
> Best regards
> Søren, AnyBody Support
>
>
> — In anyscript@yahoogroups.com, “eugeneyang40” <eugeneyang40@>
> wrote:
> >
> > Hi Jean-olivier
> >
> > Thanks for the link.
> >
> > I roughly understand the reason behind model with and without
> muscle.
> > But I am still puzzled by the large force generated. I used the
> > following and obtain my kneereaction from the ChartFX under
> > KneeReaction/F:
> >
> > AnyForceMomentMeasure KneeReaction = {
> > AnyRefFrame &Ref = .SegmentFolder.Shank.KneeJoint;
> > AnyRefFrame &Reac = .JointFolder.Knee.Constraints.Reaction; };
> >
> > The reading is different from Fout under the constraint. Why is
> that
> > so? Which should be the value for me to use. I had uploaded a
> model
> > in yahoogroup under single leg landing folder. Does the value
> > reflects the actual knee reaction force experience by the subject
> or
> > it simply due to the muscle acting on it. Sorry, I am really lost
> > with this and need to write a report on this. Pls help.
> >
> > Thank you
> >
> > Regards
> > Eugene
> >
> >
> > — In anyscript@yahoogroups.com, Jean-Olivier Racine <jean-
> > olivier.racine.1@> wrote:
> > >
> > > Hello Eugene,
> > >
> > >
> > >
> > > This post might be of interest to you.
> > >
> > > http://tech.groups.yahoo.com/group/anyscript/message/1192
> > >
> > >
> > >
> > > Cya,
> > >
> > > Jean-Olivier
> > >
> > >
> > >
> > > From: anyscript@yahoogroups.com
> [mailto:anyscript@yahoogroups.com]
> > On Behalf
> > > Of eugeneyang40
> > > Sent: Thursday, August 02, 2007 12:13 PM
> > > To: anyscript@yahoogroups.com
> > > Subject: [AnyScript] Joint Reaction Force
> > > Importance: High
> > >
> > >
> > >
> > > Hi,
> > >
> > > I facing a problem with my model. May I know what does the
joint
> > > reaction force actually measure? When I did a single right leg
> drop
> > > landing model, the peak knee reaction force is about 18800N
> which
> > is
> > > very large. It is about 40 time body weight. Why is the reading
> so
> > > large? Is it due to the absolute joint reaction force
experience
> by
> > the
> > > knee due to the muscle? pls advise.
> > >
> > > Thanks
> > >
> > > Best Regards
> > > Eugene
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
>