Connect muscles to KeepOut

User Guide > Rigging > Maya Muscle > Collision >

Once a KeepOut hierarchy is rigged, you must connect it to one or more Muscle Object nodes (such as capsules, bones or muscles) that you want it to collide against.

Select the Muscle KeepOut locator or parent group.
Ctrl-click to select the Muscle Object or objects you want it to collide against.
Select Muscle > Self/Multi Collision > Connect Muscles to KeepOut.
The nodes are now connected, and the driven group will attempt to slide along the direction provided to stay outside the connected muscle objects.

To disconnect a muscle object from a KeepOut calculation

Select the Muscle KeepOut locator or parent group, as well as the Muscle Object nodes to disconnect from.
Select Muscle > Self/Multi Collision > Disconnect Muscles from KeepOut from the main menu bar.
The node is now disconnected and no longer affects the Muscle KeepOut.