marker set

Dear AnyBody Support team,

I am working on a project that involves studying whole body motion performed in supine posture. Due to the task constraints, I cannot place any markers on the posterior surface of back or pelvis. I am using plug in gait marker set and have removed the C7, right back and mid back marker. In addition, I moved the LPSI and RPSI markers approximately to the mid-sagittal plane of pelvis. With this marker set, I collected some simple motion data and in the attached model I am trying to run AnyBody model using a C3D file.

The model loads fine, but fails towards the end of parameter optimization step. I have following queries:

  1. for the trunk motion, if only two markers on the anterior surface - “CLAV”,“STRN” are used, will that be a right thing to do. Although the AnyBody model loads fine and moves, these two markers do not form a plane.
  2. If such marker set is used, what is the accuracy of the kinematics calculated by the AnyBody model?
  3. Every time I load the Anybody model that reads from the C3D files, it fails and after I spend a lot of time to match the location of the markers, it works fine. But this matching takes a lot of time, is there a better method to do?

Thanks in advance for your help.

Hi,

I runned the model and saw that it is the kinematic of the MotionOptimization study that fails, you can try to change the kinematic tolerance of this study.
For the questions:

Considering that the pelvis position is defined, those two markers are enough to define the three rotations of the pelvis-trunk joint.

Dificult to quantify, the simple answer is the less markers you have the less accurate the motion is. But i don’t think this is an issue for your model, the simulation will be accurate enough with those markers i think.

AMMR1.3 working with AMS 5 has a new version of the gait model (GaitLowerExtremityProject) where the body markers can be moved by draging them in the model view, this is much faster and easier.

Best regards, Sylvain.