A cool feature that can be applied to both Layer and Region bound bones is Bone Dynamics. This is where we can apply physics to certain bones so they react to movement. Good examples of this would be creating feathers that react to the movement of a wing, physics-based hair, springy objects, and so forth.
Open the example file labeled BoneDynamics.anme. You will see our green friend again. This time, it looks like he's sprout some antennas! We will be applying Bone Dynamics to these two layers by performing the following steps:
Hit the Play button on your timeline to see what the animation looks like. Notice how the antennas remain stationary as the character runs.
Go back to frame 0, take the Select Bone tool, and highlight all the bones that make up the antennas. There should be a total of six bones.
Click on the Bone Constraints drop-down menu on the top bar and notice how there is an object to enable Bone Dynamics at the bottom of the panel. Check the box.
For the Torque...