Anybody Situp model

Hi, I’m very new to the Anybody software and am currently using the programme for a project on muscles used during sit ups. I am facing some problems trying to establish the model. Most of the models in the repository involves standing and placing both feet on the ground. Can anyone here guide me on how i should go about making a model in the situp position? Or maybe someone here has a model which could share with me.

Help is deeply appreciated

Hi Jared,

I think I would begin with making a copy of the FreePosture model from the Examples section of the repository and then work from there. The FreePosture model is grounded at the pelvis and you can control the posture and movement from the Mannequin file.

There is an alternative version, FreePostureMove, which gives you the ability to impose movements as interpolation functions from the Mannequin file.

I would start by getting the posture and movement right. When they work, I would change the support conditions from the grounded pelvis to what the real body feels in terms of support from the floor.

Good luck,

Hi John,

Thanks for the tip. It really helped me get started on the modelling. I’m just wondering, how do i change the constains of the model? Also, is the constrain only limited in the Z-direction?

Really appreciate your help here. So thanks!


Hi Jared,

There are many ways of adding reactions to the model and the reactions are not constrained into any particular direction.

If you have not looked at some of the tutorials yet i think you have a look at this one:

As i wrote reaction force can be applied in many ways:

[li]In joint and drivers which may have reaction switch on or off
[/li][li]using AnyReacForce which enables reaction forces without adding kinematics constraints
[/li][li]As AnyGeneral muscles which can be used to construct unilateral forces.
[/li][li]As Friction elements which can be used to create both normal force and friction forces, see jointanddrivers.any in PedalDemoConditional for example of use.

So which solution you need depends entirely on what the boundary conditions is to your model in real life. If the person is sitting on the floor? it may be a good idea to look in the SeatedHumanModel in the seatsupport.any file. It should be possible to reuse some of boundary conditions acting between pelvis and chair and shift these to act between pelvis and floor.

Best regards