Spine Rhythm Off- Kinematically Indeterminate

Hi AnyBody Team,

I am really new to the program and I want to use the basic human standing model and I want to fix the subjects lumbar spine. Since I am so new, I was trying just to turn the “BM_SPINE_RHYTHM OFF” but when I try to perform an analysis I get the error message

“…Study: Model is kinematically indeterminate: Position analysis failed :402 independent constraints and 420 unknowns”

I looked around and compared this to a study with the spine rhythm on and I can see that the missing drivers to make the model kinematically determinate are

“Main.HumanModel.BodyModel.Trunks.JointsLumbar.SpineRhythmDrv(18 constr. Segments(8):PelvisSeg Sacrum Seg L5Seg L4Seg L3Seg L2Seg L1Seg ThoraxSeg”

What should I do to make this kinematically determinate? My goal is to find the reactions are their feet just from standing with a fixed spine as opposed to a person without a fixed spine.

Thank you!


Hi Emily,

By default you don’t need to anything. The individual intervertebral angles of the lumbar spine will be set to zeros automatically. So you will have it “fixed”. Please remove this define “BM_SPINE_RHYTHM OFF” and it will work like you need it. The spine rhythm means that the angles will be automatically distributed from the thoracopelvic angle - so as long as this angle is 0, everything else will be zero too.

Best regards,