When connecting a NURBS muscle to the Muscle skin deformer, only certain points are calculated for Sticky weighting. Later on if you weight a point that was not properly bound, the deformer appears to get slower since it now calculates this information on the fly during deformation.

To fix points that have weighting to muscles that they were not originally bound to, you can use the following auto-fix option:

1. Select the mesh that has a Muscle deformer applied with Sticky weights to muscles.
2. Select Muscle > Skin Setup > Auto-Fix Invalid Sticky Bind Points from the main menu bar.

   The mesh is checked, and any muscles/points that need it are corrected.