Rigging: Digital Orthopedia - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 274

Spikes, or No Influence
Proceed through your whole armature, testing the motion of each bone to look for deformation problems.
When you find them, figure out which bone is causing the problem, select it, and adjust its influence on
the mesh with Weight Painting mode. Every so often during the process, grab one of the master control
bones and move it around. During the original binding and throughout the skinning process, it's possible
to end up with portions of your mesh that aren't influenced by any bones at all. These will show up as
“spikes” in the mesh when you move the overall control bones, or as overall areas that remain in place
when their bones are moved. Figure 9.35 shows what happens to the character's head when the whole
rig is moved.
Figure 9.35 Shriek!