This model has been set up so that the muscle movement in the arm can be seen.
There is a control included in the scene that controls the movement. This is made of a circular spline and is called ‘armCTRL’. There is an attribute on this spline called ‘arm move’. Move the spinner here to control the arm/muscle movement. As the arm moves, the biceps and triceps are set to bulge out to simulate the muscle movement. This has been wired using morph targets (included in the file).
There are also helper objects in the scene that can be used to move the lower arm muscles. For more information see the document. To see the movement see the animation.