MSkin
Basic Coord. Object MusclesMSkin
The MSkin object ties Muscle objects to the geometry of your character, in the same way that joints and the Skin object deform your mesh.
Muscle objects can be placed anywhere in the hierarchy, but it is recommended that you place the MSkin object below any existing Skin object used on a character's geometry.
This is necessary to ensure muscles deformations are applied after the joints deformations.