Specifications

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InverseDynamicAnalysis in the study tree at the bottom left of the screen and then the Run button, and
watch the model move. It should look exactly like in the kinematic analysis, however, during this analysis,
the AnyBody system computes all muscle and joint forces in addition to a whole lot of other useful
information. To see it, you once again have to open a ChartFX window (if you don't have the one we used
previously open) by means of the menu Window -> ChartFX 2D (new) in the pull down menus in the top of
the main frame. In this new window, expand the ArmStudy -> Output -> Model -> Muscles branch. You
should see a list of all the muscles appearing. Each of them can be expanded to reveal the data inside. Let
us expand the brachialis muscle and investigate its force variation over the movement. You should see a
node named Fm. If you click it, you should get a curve like the one shown below:
Notice that the force in the muscle drops as the movement proceeds. This is quite as expected, because the
moment arm of the gravity about the elbow gets smaller as the elbow flexes, and less muscle force is
therefore needed to carry it. If you look at the muscle force in the BicepsLong, you see a different pattern: