meaning of variable from getLinearAccelerationInGround

[Hide Kimpara]

Dear Experts,
It was long time silence in this forum. I restarted to use the OpenSim in recent.
I have a question about "getLinearAccelerationInGround".
Body acceleration data are available in Analysis Tool of GUI software. However, in order to simulate outputs of accelerometers on the body during movement, I tried to use a function of "getLinearAccelerationInGround".
When I use this function with a simplified pendulum model, the output variables look similar with acceleration of body kinematics in global.
However, I applied this function to a skeletal muscle model, the output shows quite different from acceleration of bodykinematics obtained from Analysis with IK, RRA, and CMC analysis.
What makes this difference? If I need to make values of "getLinearAccelerationInGround" similar as the bodykinematics, what kind of methods are necessary?

Thank you and Best,
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