02.04
Most than a tutorial this is a simple explanation about how to use some modifiers and constrains to made a muscle system on Blender.
Fist at all here is the .blend, for the inpatients 
If you open the file you will see some like these:
There are a Leg mesh, and a Muscle, Tendon and Heel meshes.
Playing with the layer you will find an armature:
There is a couple of Green bones, what that mean? well, these bones have a Constraint like these:
With the constraint the bone will have the muscle behaviour, stretching and flattening. You could make a constraint selecting first the bone to the muscle will be attached, then maintaining shift selecting the Muscle Bone (¿?), theeen doing Ctrl+Shift+C and selecting Stretch Constraint. The Muscle or Tendon object must be attached to these bones (Ctrl+P).
About how to deform the leg mesh you must to apply a ShrinkWrap modifier to the leg object.
Then you can apply some SoftBody simulations to the Muscle and its done! You have a full realistic leg rig 
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Thank you for this! You have explained clearly and quickly, everything I needed to know about this to finish a project I am working on.
As an added note; You can optimize the speed of the shrink wrap modifier, if you delete any faces on the muscles that will not come into contact with the mesh to be deformed.
Thank you.
Muy buena la explicación. El inconveniente que tuve es que no pude bajar el .blend. Si podes arreglar el link estaría más que agradecido.
Corregido el link!
Buenisimo!!! Mil gracias!!! No sabes lo que estoy renegando con el blender para que la malla se desforme como la gente. Visite todo internet pero en el único lugar que encontré la explicación que buscaba fue acá.
Repito, mil gracias!!!
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