How to simulate muscles under skin?
Is it possible to do it in standard software like Max and Maya?
Or do I need a special muscle system plugin to do this?
Thank you.

You can fake the muscle under the skin in different ways.
One is to use modifiers that depend on the angle of the bones like latices and bulges and morphs.
Another is to use additional bones for animation.
And the last one is to use actual muscle geometry that will defform acordingly in combination with some warp modifier.
Hope it helps.