Specifications

Try clicking Ekin, Epot, and Emech in turn. You will notice that Epot and Emech are very similar. This is

because the movement in this model is relatively slow, so the kinetic energy remains small throughout the

simulation and has little influence.

The KinematicError is not very interesting unless something is wrong with the analysis. It stores the error

in the kinematic analysis as a measure of how far the kinematic constraints of the problem are from being

satisfied. Normally this should be zero or very close to zero. If is it not, information about the development

of the kinematic error may help you determine the cause of the problem.

Finally, the MaxMuscleActivity is the a measure of the overall effort of the body model but it requires

further explanation, so we shall get to it a little later.

Time-dependent data

The predominant way of looking at data is as a function of time or rather time steps. If you expand the

Model branch into the Segs section, you can investigate the movement of the "hand" of the model as shown

in the figure above.

Expand the tree until you get to the HandNode object as shown to the left. Then click the r property. This

displays three curves on the screen corresponding to the x, y, and z coordinates of the handnode as the arm

moves. The z coordinate is zero because it is a 2-D problem. By the way, the color codes of the chart view

are red, green and blue in that order, so red is for x, green is for y, and blue is for z.

Let us look as more complex data. Most users of musculoskeletal analysis are interested in muscle forces. In

this model we can find the muscles in the tree by expanding the nodes Main.Model.Muscles. Take the first

muscle, brachialis, and click the Fm property.

Fm is the muscle force, and as you can see, the brachialis force declines as the arm moves. Not all of the

muscle data items in the tree contain any reasonable results. It depends a bit on the muscle model in

question. But the muscle force, Fm, and the active state, Activity, are always available. Please refer to the

Muscle Modeling tutorial

for more information.

Detailed data investigation