Using motion files with constraints

[Isabelle E]

Hey,

I'm a student currently writing my thesis using opensim. I'm really new to the program, I've just finished the first three tutorials. I'm now interested in muscle activation in the trunk. Therefore I downloaded some available lumbar spine models. Most of them have coupled coordinate constraints. So this means the total flexion of the trunk is represented by one independend coordinate (L5_S1_Flex) and the other lumbar vertebraes (L4_L5, ...) are dependend coordinates.
When I use the slider in the coordinate window for SPINE_flexion and extension of the trunk you can see, that the motion is a summary of small motions of all the lumbar vertebraes (So the coupler coordinate constraints are active).
But when I use a motion file as input (comes in the download folder of the model) in which only the independend coordinate (SPINE_flexion) is given in degrees, only that specific joint is moving and all the others (which I thought are coupled) are fixed or "welded", so they are not moving.

Motion file:
flex45andback5sec10Hz_3DOF
version=1
nRows=51
nColumns=5
inDegrees=yes
endheader
time PELVIC_rot SPINE_flexion SPINE_latbend SPINE_rotation
0.00000000 0.00000000 0.00000000 0.00000000 0.00000000
0.10000000 0.00000000 -0.17741922 0.00000000 0.00000000
0.20000000 0.00000000 -0.70687887 0.00000000 0.00000000
0.30000000 0.00000000 -1.58002907 0.00000000 0.00000000
0.40000000 0.00000000 -2.78309970 0.00000000 0.00000000
0.50000000 0.00000000 -4.29711763 0.00000000 0.00000000
0.60000000 0.00000000 -6.09820588 0.00000000 0.00000000
0.70000000 0.00000000 -8.15796023 0.00000000 0.00000000
0.80000000 0.00000000 -10.44389711 0.00000000 0.00000000

So my question now is: How do I generate a trunk - flexion movement? (I'm gonne use vicon system later on, but wanted to check which model to use by using existing motion files).
Do I have to manually type in all the different angles of the vertebraes? I thought thats what the coupled coordinate constraints are for?

Thank you so much for your answers!!
Isabelle