Go here --> [link]
<-- for the tutorial.
A really quick and sloppy tutorial on making muscles bulge automatically, with 3dsmax.
I thought I would mention that the whole reaction manager driven morph target thing in here is useful for a LOT more then just a muscle bulge.
In this tutorial, I make a morph target for the arm where the bicep is enlarged, and when the bone bends, the morph comes on.
This can be used for any kind of adjustment/fix to the rig, not just muscles.
You could make a morph for a skirt to deform better when legs are bent.
You could make a morph for wrinkles on clothes to bunch up when an arm is bent.
you could make a morph for... Well, any specific change you need to happen, when something bends, that doesn't happen automatically as apart of the skin.
Another option is to use the modifier Skin Morph, however I'm not terribly fond of it, because I don't feel I have nearly enough control with it.
There are LOTS of things that you can apply these techniques towards.
In this example, the value of the ExposeTM's bone's local rotate value is the controller - the Driver, or the Master.
The value of the morph target is the driven or the Slave. But anything can be the slave, not just a morph target.
If you have a very dense mesh (lots of geometry) instead of a morph target, you could control the opacity of a displacement map.
Then the black-and-white displacement map, will create geometry displacement when the opacity is turned up.
Lots of things can be done with this sort of technique.