The topics covered in this section include:
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 | - The ExternalLoads editor dialog window shown on the left will appear when the editor button
 is clicked. - The Force data file specified at the top of this dialog window is a .mot or .sto file containing experimental data. The labels in this file have to be unique so that there's no ambiguity regarding which columns are used to define the forces.
- In case the column labels are not unique, the OpenSim GUI will detect that and offer the option to overwrite or write a new file with unique labels. Earlier versions of OpenSim allowed for duplicate column names but this behavior has been deprecated.
- Underneath you can specify the Kinematics for external loads file, filtering options for this file, and a list of ExternalForce(s) and/or torques that have been defined so far. In general, you should leave this blank. OpenSim will then use the specified kinematics that are being tracked by ID, RRA, and CMC (e.g. for ID for RRA it would be IK kinematics, and for CMC it would be RRA kinematics), which is generally more accurate.
- You must select Save… after you define your forces in order to write them to the XML file that will be used by the tool.
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 | - You can select any of the listed forces and/or torques for editing or deletion by choosing it and then clicking on the Edit… or Delete buttons, respectively.
- Click on the Add… button to add a new force and/or torque to the list.
- Choosing the Add… button opens the dialog window (Create/Edit ExternalForce) shown in the figure on the left.
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Within the Create/Edit ExternalForce window, you can define either a Point Force or a Body Force.
- A point force (most commonly used) is a force applied at a specified point and an optional torque. Using the drop down menu at the bottom of the window, you can specify the reference frames that the point and the force are expressed in.
- A body force is a force applied to the origin of the body frame (not necessarily the CoM) and a required torque, for a total of six components. By definition, a torque is a rotational "force" or moment so the point of application does not need to be specified. Thus for a body force, you should check applies force and applies torque. The selections in "Point Columns", "Force Expressed In", and "Point Expressed In" will be ignored.
The drop-down menus for Force Columns, Point Columns, and Torque Columns allow you to specify which of the columns in the Force Data file are to be used to define the ExternalForce. Columns in the Force data file corresponding to the same force are assumed to live in adjacent columns and to have a common prefix that's used as an identifier for the corresponding ExternalForce. This common prefix is stored in the xml file as a "force_identifier", similar rules apply for the "point_identifier" in case a point needs to be specified and "torque_identifier" for the case when a torque is also applied. Other attributes of the ExternalForce are:
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