There is no keyframing with spline IK. It is a dynamic chain... Think you are confused...

Iron Shackles Dynamic Chain Rig - Maya - YouTube

That is a video of the same thing I do in C4D. The geo is simply bound to the spline so the chain itself is not the driving force in this video. Much like how you would make a dynamic animal tail. You could use a hinge connector as well through traditional dynamics but I am thinking it will create a force that is constricted and not realistic. However even with the Spline IK it will be tough to show the transference of energy from the most outer balls... Many ways my friend...