Muscle Groups
Muscle groups are defined in the .osim model to be used in the pipeline. If you are using the RCNL Model, a number of muscle groups are already defined in the model for ease of use. The RCNL model can also be used as a reference for recommended groups.
Activation Groups
Reference in MTP and NCP XML files: <activation_muscle_groups>
Activations of certain muscles should be approximately the same. One example of this is the VasActivationGroupR which includes the three vasti because we would expect all three to have similar activations.
Fiber Length Groups
Reference in MTP XML file as the element: <normalized_fiber_length_muscle_groups>
Normalized fiber lengths of certain muscles should be approximately the same. For example, all three lines of action for the glutes should be similar. GlutmaxNormalizedFiberLengthGroupR is in the RCNL Model to describe this relationship.
There may be overlap between fiber length groups and activation groups for some groups, but other groups may be different. Simpler muscle groups like the glutes will have overlap while more complex groups like ankle invertors will differ.
Collected EMG Groups
Reference in MTP XML file: <collected_emg_channel_muscle_groups>
Only a finite number of EMGs can be placed on the subject for experimental data collection. A single EMG may be collecting muscle excitation information about multiple muscles. An EMG scale factor group, like GlutmaxMeasuredEMGChannelGroupR in the RCNL Model, can be used to describe this relationship. Unlike the other groups, it is required that these groups have the same name as the corresponding EMG channel in your EMG .sto file.
Missing EMG Groups
Reference in MTP and NCP XML file: <missing_emg_channel_muscle_groups>
Similar to the collected EMG group, the missing EMG groups are groups of muscles without EMG data. The missing EMG groups will be filled in by synergy extrapolation at the start of MTP, which finds the optimal approximation of the excitations of included muscles.