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The .osimx File Type

Because model properties that are not described in OpenSim model files (.osim) are optimized and used across the NMSM Pipeline, an addendum file of the type .osimx is saved and passed between tools. The specifics of these files are discussed here.

Muscle Properties​

The following elements can be included in the muscle properties of the .osimx XML file inside an <RCNLMuscleSet>:

  • <electromechanical_delay>
  • <activation_time_constant>
  • <activation_nonlinearity_constant>
  • <emg_scale_factor>
  • <optimal_fiber_length>
  • <tendon_slack_length>
  • <max_isometric_force>

Ground Contact Properties​

The .osimx file also includes ground contact properties that can be used to inform Treatment Optimization.

Contact surface elements contain information inside an <RCNLContactSurfaceSet> about the GCP results to fully describe the personalization:

  • <resting_spring_length>
  • <dynamic_friction_coefficient>
  • <viscous_friction_coefficient>
  • <damping_factor>
  • <latching_velocity>
  • <belt_speed>

Synergy Sets​

The .osimx file includes muscle synergy information that informs Treatment Optimization how muscles are grouped into synergies.

The following elements are included in an <RCNLSynergySet>:

  • <muscle_group_name>
  • <num_synergies>