# Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodytech.com/662.0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanModel.Trunk.JointsLumbar.L5SacrumJnt;
F = -100.0*Main.Model.HumanModel.Trunk.JointsLumbar.L5SacrumJnt.Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output.Model.HumanModel.Trunk.JointsLumbar.L5SacrumJnt.Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogroups.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodytech.com/662.0.html>
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanModel.Trunk.JointsLumbar.L5SacrumJnt;
F = -100.0*Main.Model.HumanModel.Trunk.JointsLumbar.L5SacrumJnt.Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

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

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment?Â How do I solve for the shear force?
Â
Also, I found AnyFroceMomentMeasure which appears to give me the resultant force
and moment at any point I specify.Â I am using it this way:
{
};AnyForceMomentMeasure2L3Reaction = AnyForceBase&Muscles1 =
Main.Model.HumanModel.Trunk.MusclesSpineRight.ErectorSpinae.ILplL1CI;AnyForceBas
e&Muscles2 =
Main.Model.HumanModel.Trunk.MusclesSpineRight.ErectorSpinae.ILplL2CI;AnyRefFrame
& L3Seg= Main.Model.HumanModel.Trunk.SegmentsLumbar.L3Seg;
I believe that function is using the L3 segment as a reference point and then
taking the forces from whatever I define (i.e. Muscles1 and Muscles2) and
solving for both the applied force and moment at the reference frame I assign
(which in this case is L3 segment).Â IsÂ my interpretation correct?Â
Â
Thank you very much for all of your help…Â I really appreciate it.
Â
Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@anybodytech.com>
To: anyscript@yahoogroups.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

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

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

Hi Lacey,

For a joint the output …Constraints.Reaction.Fout gives you all the
component of the reaction depending on the type of joint. L5SacrumJnt is a
spherical joint, so there are three reactions for the three locked
translation and no reactions for the three free rotations. In the ChartFX
window you can see three components for this joint reaction force: one is
compression, one is lateral shear and one is frontal shear. You can draw the
joint node frame to see exactly which of x y and z axis correspond to which
force.

Your understanding of the AnyForceMomentMeasure2 is correct. You can also
look in the reference manual, there is a detailed description of this
functionality.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Lacey Bresnahan
Sent: 21. august 2008 19:30
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment? How do I solve for the shear force?

Also, I found AnyFroceMomentMeasure which appears to give me the resultant
force and moment at any point I specify. I am using it this way:
{
};AnyForceMomentMeasure2L3Reaction = AnyForceBase&Muscles1 =
Main.Model.HumanModel.Trunk.MusclesSpineRight.ErectorSpinae.ILplL1CI;AnyForc
eBase&Muscles2 =
Main.Model.HumanModel.Trunk.MusclesSpineRight.ErectorSpinae.ILplL2CI;AnyRefF
rame& L3Seg= Main.Model.HumanModel.Trunk.SegmentsLumbar.L3Seg;
I believe that function is using the L3 segment as a reference point and
then taking the forces from whatever I define (i.e. Muscles1 and Muscles2)
and solving for both the applied force and moment at the reference frame I
assign (which in this case is L3 segment). Is my interpretation correct?

Thank you very much for all of your help… I really appreciate it.

Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsup%40anybodytech.com>
anybodytech.com>
To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt.
Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On
Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

[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]

Sylvain,
I have been working with the AnyForeceMomentMeasure2 for the past week.Â I
haveÂ three questions:
1.Â How is Fout calculated when using …Constraints.Reaction.Fout for the
spherical joints?
2.Â When using AnyForceMomentMeasure2 I have included all the muscles as well as
AnySeg L4 and L5, however the forces that are generated using this …Measure2
are not the same as the forces from …Constraints.Reaction.Fout.Â Any idea why
this is?
3.Â How can I verify that the moment I am measuring using …Measure2 is
correct?
Thank you again for all of your assistance.
Lacey Bresnahan

----- Original Message ----
From: anyscriptsup <anyscriptsup@anybodytech.com>
To: anyscript@yahoogroups.com
Sent: Friday, August 22, 2008 8:08:04 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

For a joint the output …Constraints. Reaction. Fout gives you all the
component of the reaction depending on the type of joint. L5SacrumJnt is a
spherical joint, so there are three reactions for the three locked
translation and no reactions for the three free rotations. In the ChartFX
window you can see three components for this joint reaction force: one is
compression, one is lateral shear and one is frontal shear. You can draw the
joint node frame to see exactly which of x y and z axis correspond to which
force.

Your understanding of the AnyForceMomentMeasu re2 is correct. You can also
look in the reference manual, there is a detailed description of this
functionality.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On Behalf
Of Lacey Bresnahan
Sent: 21. august 2008 19:30
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment? How do I solve for the shear force?

Also, I found AnyFroceMomentMeasu re which appears to give me the resultant
force and moment at any point I specify. I am using it this way:
{
};AnyForceMomentMea sure2L3Reaction = AnyForceBase& Muscles1 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL1CI;
AnyForc
eBase&Muscles2 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL2CI;
AnyRefF
rame& L3Seg= Main.Model.HumanMod el.Trunk. SegmentsLumbar. L3Seg;
I believe that function is using the L3 segment as a reference point and
then taking the forces from whatever I define (i.e. Muscles1 and Muscles2)
and solving for both the applied force and moment at the reference frame I
assign (which in this case is L3 segment). Is my interpretation correct?

Thank you very much for all of your help… I really appreciate it.

Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt.
Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

[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]

Hi Lacey,

I think this is a matter of reference frame: in …Constraints.Reaction.Fout
for a joint the reaction forces are given in the ref frame of the first node
defined in the joint.

In AnyForceMomentMeasure2 there is a member called AnyRefFrame. The function
will give you the equivalent force and moment (for the sum of all the forces
you specified) at this particular point (AnyRefFrame) you specified and
expressed in global coordinate system.

So it is normal that the forces are different because you are not measuring
exactly the same forces.

To be able to compare the two output forces it requires a lot of precision
and it could be quite difficult with such a complex model. You should of
course use the appropriate point of interest, the joint node in this case.
Then make the precise list of all the muscles and segments contributing on
this reaction, you cannot miss even one, this is the complex part. And at
least do some coordinate transformation to have the results in the same
coordinate system.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Lacey Bresnahan
Sent: 28. august 2008 23:54
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

Sylvain,
I have been working with the AnyForeceMomentMeasure2 for the past week. I
have three questions:

1. How is Fout calculated when using …Constraints.Reaction.Fout for the
spherical joints?
2. When using AnyForceMomentMeasure2 I have included all the muscles as
well as AnySeg L4 and L5, however the forces that are generated using this
…Measure2 are not the same as the forces from …Constraints.Reaction.Fout.
Any idea why this is?
3. How can I verify that the moment I am measuring using …Measure2 is
correct?
Thank you again for all of your assistance.
Lacey Bresnahan

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsup%40anybodytech.com>
anybodytech.com>
To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
Sent: Friday, August 22, 2008 8:08:04 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

For a joint the output …Constraints. Reaction. Fout gives you all the
component of the reaction depending on the type of joint. L5SacrumJnt is a
spherical joint, so there are three reactions for the three locked
translation and no reactions for the three free rotations. In the ChartFX
window you can see three components for this joint reaction force: one is
compression, one is lateral shear and one is frontal shear. You can draw the
joint node frame to see exactly which of x y and z axis correspond to which
force.

Your understanding of the AnyForceMomentMeasu re2 is correct. You can also
look in the reference manual, there is a detailed description of this
functionality.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On
Behalf
Of Lacey Bresnahan
Sent: 21. august 2008 19:30
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment? How do I solve for the shear force?

Also, I found AnyFroceMomentMeasu re which appears to give me the resultant
force and moment at any point I specify. I am using it this way:
{
};AnyForceMomentMea sure2L3Reaction = AnyForceBase& Muscles1 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL1CI;
AnyForc
eBase&Muscles2 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL2CI;
AnyRefF
rame& L3Seg= Main.Model.HumanMod el.Trunk. SegmentsLumbar. L3Seg;
I believe that function is using the L3 segment as a reference point and
then taking the forces from whatever I define (i.e. Muscles1 and Muscles2)
and solving for both the applied force and moment at the reference frame I
assign (which in this case is L3 segment). Is my interpretation correct?

Thank you very much for all of your help… I really appreciate it.

Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt.
Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

[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]

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

That makes sence.Â Do you know if it is possible to find which forces are
contributing the the calculation of …Constrains.Reaction.Fout?Â I think that
would help me to ensure I am including everything I should.

Thank you again,

Lacey Bresnahan
Rush University Medical Center
Chicago, IL USA

----- Original Message ----
From: AnyScript Support <anyscriptsup@anybodytech.com>
To: anyscript@yahoogroups.com
Sent: Friday, August 29, 2008 4:33:12 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

I think this is a matter of reference frame: in …Constraints. Reaction. Fout
for a joint the reaction forces are given in the ref frame of the first node
defined in the joint.

In AnyForceMomentMeasu re2 there is a member called AnyRefFrame. The function
will give you the equivalent force and moment (for the sum of all the forces
you specified) at this particular point (AnyRefFrame) you specified and
expressed in global coordinate system.

So it is normal that the forces are different because you are not measuring
exactly the same forces.

To be able to compare the two output forces it requires a lot of precision
and it could be quite difficult with such a complex model. You should of
course use the appropriate point of interest, the joint node in this case.
Then make the precise list of all the muscles and segments contributing on
this reaction, you cannot miss even one, this is the complex part. And at
least do some coordinate transformation to have the results in the same
coordinate system.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On Behalf
Of Lacey Bresnahan
Sent: 28. august 2008 23:54
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

Sylvain,
I have been working with the AnyForeceMomentMeas ure2 for the past week. I
have three questions:

1. How is Fout calculated when using …Constraints. Reaction. Fout for the
spherical joints?
2. When using AnyForceMomentMeasu re2 I have included all the muscles as
well as AnySeg L4 and L5, however the forces that are generated using this
…Measure2 are not the same as the forces from …Constraints. Reaction. Fout.
Any idea why this is?
3. How can I verify that the moment I am measuring using …Measure2 is
correct?
Thank you again for all of your assistance.
Lacey Bresnahan

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Friday, August 22, 2008 8:08:04 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

For a joint the output …Constraints. Reaction. Fout gives you all the
component of the reaction depending on the type of joint. L5SacrumJnt is a
spherical joint, so there are three reactions for the three locked
translation and no reactions for the three free rotations. In the ChartFX
window you can see three components for this joint reaction force: one is
compression, one is lateral shear and one is frontal shear. You can draw the
joint node frame to see exactly which of x y and z axis correspond to which
force.

Your understanding of the AnyForceMomentMeasu re2 is correct… You can also
look in the reference manual, there is a detailed description of this
functionality.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of Lacey Bresnahan
Sent: 21. august 2008 19:30
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment? How do I solve for the shear force?

Also, I found AnyFroceMomentMeasu re which appears to give me the resultant
force and moment at any point I specify. I am using it this way:
{
};AnyForceMomentMea sure2L3Reaction = AnyForceBase& Muscles1 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL1CI;
AnyForc
eBase&Muscles2 =
Main…Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL2CI;
AnyRefF
rame& L3Seg= Main.Model.HumanMod el.Trunk. SegmentsLumbar. L3Seg;
I believe that function is using the L3 segment as a reference point and
then taking the forces from whatever I define (i.e. Muscles1 and Muscles2)
and solving for both the applied force and moment at the reference frame I
assign (which in this case is L3 segment). Is my interpretation correct?

Thank you very much for all of your help… I really appreciate it.

Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt.
Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

[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]

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

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

Hi Lacey,

It’s a very detailed and long task to list all the forces contributing to
the joint reaction forces, you can easily forget some of them and it will
probably be long before you have it right. I think I have lost at some point
your real objective, and I have the feeling that this big calculation could
be a waste of time if it is just to check the result of
…Constrains.Reaction.Fout. I mean the system uses the same equations and
solver to calculate both output. So once you would have the correct list of
forces you would without doubt get the same values.

I think you should consider what is it you want to measure exactly with
ForceMomentMeasure2 before going on in such a task.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of Lacey Bresnahan
Sent: 29. august 2008 16:32
To: anyscript@yahoogroups.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

That makes sence. Do you know if it is possible to find which forces are
contributing the the calculation of …Constrains.Reaction.Fout? I think
that would help me to ensure I am including everything I should.

Thank you again,

Lacey Bresnahan
Rush University Medical Center
Chicago, IL USA

----- Original Message ----
From: AnyScript Support <anyscriptsup@
<mailto:anyscriptsup%40anybodytech.com> anybodytech.com>
To: anyscript@yahoogrou <mailto:anyscript%40yahoogroups.com> ps.com
Sent: Friday, August 29, 2008 4:33:12 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

I think this is a matter of reference frame: in …Constraints. Reaction.
Fout
for a joint the reaction forces are given in the ref frame of the first node
defined in the joint.

In AnyForceMomentMeasu re2 there is a member called AnyRefFrame. The
function
will give you the equivalent force and moment (for the sum of all the forces
you specified) at this particular point (AnyRefFrame) you specified and
expressed in global coordinate system.

So it is normal that the forces are different because you are not measuring
exactly the same forces.

To be able to compare the two output forces it requires a lot of precision
and it could be quite difficult with such a complex model. You should of
course use the appropriate point of interest, the joint node in this case.
Then make the precise list of all the muscles and segments contributing on
this reaction, you cannot miss even one, this is the complex part. And at
least do some coordinate transformation to have the results in the same
coordinate system.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On
Behalf
Of Lacey Bresnahan
Sent: 28. august 2008 23:54
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

Sylvain,
I have been working with the AnyForeceMomentMeas ure2 for the past week. I
have three questions:

1. How is Fout calculated when using …Constraints. Reaction. Fout for the
spherical joints?
2. When using AnyForceMomentMeasu re2 I have included all the muscles as
well as AnySeg L4 and L5, however the forces that are generated using this
…Measure2 are not the same as the forces from …Constraints. Reaction.
Fout.
Any idea why this is?
3. How can I verify that the moment I am measuring using …Measure2 is
correct?
Thank you again for all of your assistance.
Lacey Bresnahan

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Friday, August 22, 2008 8:08:04 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

For a joint the output …Constraints. Reaction. Fout gives you all the
component of the reaction depending on the type of joint. L5SacrumJnt is a
spherical joint, so there are three reactions for the three locked
translation and no reactions for the three free rotations. In the ChartFX
window you can see three components for this joint reaction force: one is
compression, one is lateral shear and one is frontal shear. You can draw the
joint node frame to see exactly which of x y and z axis correspond to which
force.

Your understanding of the AnyForceMomentMeasu re2 is correct… You can also
look in the reference manual, there is a detailed description of this
functionality.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of Lacey Bresnahan
Sent: 21. august 2008 19:30
To: anyscript@yahoogrou ps.com
Subject: Re: [AnyScript] Joint Reaction Forces and Moments

When I am using Main.Study.Output. Model.HumanModel .Trunk.JointsLum
bar.L5SacrumJnt. Constraint
s.Reaction.Fout in AnyChart does that provide me with the total compression
force at that segment? How do I solve for the shear force?

Also, I found AnyFroceMomentMeasu re which appears to give me the resultant
force and moment at any point I specify. I am using it this way:
{
};AnyForceMomentMea sure2L3Reaction = AnyForceBase& Muscles1 =
Main.Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL1CI;
AnyForc
eBase&Muscles2 =
Main…Model.HumanMod el.Trunk. MusclesSpineRigh t.ErectorSpinae. ILplL2CI;
AnyRefF
rame& L3Seg= Main.Model.HumanMod el.Trunk. SegmentsLumbar. L3Seg;
I believe that function is using the L3 segment as a reference point and
then taking the forces from whatever I define (i.e. Muscles1 and Muscles2)
and solving for both the applied force and moment at the reference frame I
assign (which in this case is L3 segment). Is my interpretation correct?

Thank you very much for all of your help… I really appreciate it.

Lacey

----- Original Message ----
From: anyscriptsup <anyscriptsup@ <mailto:anyscriptsu p%40anybodytech. com>
anybodytech. com>
To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
Sent: Thursday, August 21, 2008 2:33:35 AM
Subject: RE: [AnyScript] Joint Reaction Forces and Moments

Hi Lacey,

With this piece of code you are creating a moment in the L5Sacrum joint,
this moment is proportional to the rotation of the joint. In the neutral
position there is no moment applied to the joint and then the moment
increase with the angle.

This moment should represent the stiffness of the spine. You can visualize
it in the ChartFX window browsing through the model tree to the location you
included it.

Regarding to the joint reaction forces you can investigate the linear
reaction forces, due to the compression for example in
Main.Study.Output. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt.
Constraint
s.Reaction.Fout. But the lumbar joints don’t provide reaction forces as
moments because the joints are modelled as a spherical joints. So the
reaction to the spring force you applied is carried by the muscles, and it
is difficult to separate this particular reaction force from all the others
the muscles also carry.

Best regards,

Sylvain, AnyBody Support.

From: anyscript@yahoogrou ps.com [mailto:anyscript@ yahoogrou ps.com] On
Behalf
Of lebresnahan
Sent: 19. august 2008 23:33
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Joint Reaction Forces and Moments

I am working with the spine model and I am trying to understand how I
can measure the joint reaction forces and moments. I have followed the
tutorial at http://www.anybodyt <http://www.anybodyt ech.com/662. 0.html>
ech.com/662. 0.html to add the spring
force. However, I am not sure how I actually measure the moment. I am
using:
AnyForce L5S1Spring = {
AnySphericalJoint &L5S1Hinge =
Main.Model.HumanMod el.Trunk. JointsLumbar. L5SacrumJnt;
F = -100.0*Main. Model.HumanModel .Trunk.JointsLum bar.L5SacrumJnt. Pos;
};

If you could please tell me what I am measuring using this constraing
and what the output represents I would appreciate it.

Thank you,
Lacey Bresnahan

Department of Orthopedic Surgery
Rush University Medical Center
Chicago, IL

[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]

[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]