# friction at joints/ insertion points

Hi,

We have found the demo trial very useful and feel that AnyBody will certainly
meet our needs. I just have a few final queries that I hope you would be able to

Do you know if friction in the joints can be taken into account?

Is it possible to have muscle origins/insertions fanned over an area on the
segment?

Many Thanks

Simon

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Hello Simon,

> We have found the demo trial very useful and feel that AnyBody will
> certainly meet our needs. I just have a few final queries that I
> hope you would be able to answer:

Thanks for your kind words and for posting the questions here for the
benefit of other users.

> Do you know if friction in the joints can be taken into account?

This is possible, at least if you know the size of the friction
torque. There is no easy way to make AnyBody compute the friction
force automatically based on normal force (but we are thinking a lot
about how it can be done). If you know the size of the friction
torque, then the solution is to use an AnyForce object. It is an
abstract representation of force that attaches to kinematic measures.
If the measure is linear, then AnyForce becomes a linear force in the
direction of the measure. If the measure is an angle, then the
AnyForce becomes a torque.

Any joint in AnyBody has an angle measure inside it. If you attach an
AnyForce to such an angle, then you are imposing the torque you
specify in the AnyForce to the joint, and the muscles spanning the
joint must carry that torque in addition to whatever else the muscles
do.

> Is it possible to have muscle origins/insertions fanned
> over an area on the segment?

Muscles in AnyBody are string elements, so the standard method is to
attach them to the bone at the center of gravity of their true
insertion area. However, some muscles have such wide attachments that
it is not reasonable to perceive them as one muscle. The pectoralis,
for instance, has a very wide origin on the rib cage and fans out in
different directions from its insertion on the humerus. Such a muscle
will also have many motor units, so that it mechanically functions as
several muscles contrary to its anatomical definition.

So, in AnyBody we model such muscles in several independent units as
shown in this video, where you can see how the pectoralis branches
get recruited individually.

Best regards,
AnyBody Support