Rigging and Skinning - Animating with Blender: How to Create Short Animations from Start to Finish - page 139

Figure 9.19 (Continued)
Each axis can also be assigned a degree of “stiffness.” In this context, stiffness is the amount of resistance a
joint puts up before it begins to move. For the mother's collarbones, I only wanted them to move when the
rest of the arm was completely extended, so I assigned the X- and Z-axes a very high value of stiffness: 0.9.
The highest level of stiffness is 0.99, and the lowest is 0, which is the default. Working with stiffness on IK
joints has a bit of an artistic voodoo to it because stiffness values for one joint can affect the way that stiff-
ness works with other joints in the chain. The most reliable method for making use of it is to apply it to the