The old way of sumultaing muscle in Maya was a total pain in the a**e to set up and would have been dealt with by either the modeller or rigger.
As far as I ever read deformers were used to push and pull spheres or created objects using SDKs and MEL (i think) to allow a bone joint to bend and at the same time deform the muscle, then the outer layer of skin would be forced to react using soft bodies ( i may have this totaly wrong, but this is how I read it).
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