IK to FK and vice versa
When having freeform forward kinematic animation - such as motion capture input - you may want to assign an IK solver to the animated chain - doing this will not destroy the underlying animation - and using this script - you will be able to snap the IK Solver Goal motion to the FK animation.
Once done - you can optimize the IK Goal tracks and you end up with the same animation - but as an optimized IK motion - much easier to adjust.
Btw - yet again a little sample file to better understand what I'm talking about : fk2ik_Sample.max