Error running Forward Dynamics Full Body Lumbar Spine Model (FBLS)

[Saadia Talay]

I am trying to figure out the changes in motion due to a change in muscle forces. For this purpose I am trying to run Forward Dynamics on the Full-body Musculoskeletal Model of the Lumbar Spine https://simtk.org/projects/fullbodylumbar/.

I scale the model, run the inverse kinematics, RRA, and static optimization (SO) before running the forward dynamics tool. For the forward dynamics, I use the controls and states from the SO results and actuators from both the RRA and SO folders.

However, the model crumples up and I get the following errors:

(nr=870 nc=765)
Found 870 state vectors with time stamps ranging
from 0 to 0.855667.

Using dt specified from storage UNKNOWN
WARNING: No suitable initial conditions found for
glut_max2_l:
by

WARNING: Thelen2003Muscle::computeInitialFiberEquilibrium(SimTK::State& s)
Continuing with an initial fiber force and length of 0 and 0.145221
Here is a report from the routine:

Solution Error : 103.457523 > tol (0.000008)
Newton Iterations : 200 of max. iterations (200)
Check that the initial activation is valid, and that the whole
length doesn't produce a pennation angle of 90 degrees, nor a fiber
length less than 0:
Activation : 0.050000
Whole muscle length : 1.#QNAN0


WARNING: No suitable initial conditions found for
glut_max3_l:
by

WARNING: Thelen2003Muscle::computeInitialFiberEquilibrium(SimTK::State& s)
Continuing with an initial fiber force and length of 0 and 0.142259
Here is a report from the routine:

Solution Error : 138.687300 > tol (0.000006)
Newton Iterations : 200 of max. iterations (200)
Check that the initial activation is valid, and that the whole
length doesn't produce a pennation angle of 90 degrees, nor a fiber
length less than 0:
Activation : 0.050000
Whole muscle length : 1.#QNAN0


WARNING: No suitable initial conditions found for
ext_dig_l:
by

WARNING: Thelen2003Muscle::computeInitialFiberEquilibrium(SimTK::State& s)
Continuing with an initial fiber force and length of 0 and 0.104029
Here is a report from the routine:

Solution Error : 140.958515 > tol (0.000005)
Newton Iterations : 200 of max. iterations (200)
Check that the initial activation is valid, and that the whole
length doesn't produce a pennation angle of 90 degrees, nor a fiber
length less than 0:
Activation : 0.050000
Whole muscle length : 1.#QNAN0


WARNING: No suitable initial conditions found for
ext_hal_l:
by

WARNING: Thelen2003Muscle::computeInitialFiberEquilibrium(SimTK::State& s)
Continuing with an initial fiber force and length of 0 and 0.113900
Here is a report from the routine:

Solution Error : 43.928155 > tol (0.000002)
Newton Iterations : 200 of max. iterations (200)
Check that the initial activation is valid, and that the whole
length doesn't produce a pennation angle of 90 degrees, nor a fiber
length less than 0:
Activation : 0.050000
Whole muscle length : 1.#QNAN0


What should I do to fix these?