One workaround I figured I'd share in case it helps anyone is to increase the frame range to double the amount of the loop, then select all the keyframes in the animation pallette, then alt+drag them all to the right until it fits into the empty keyframes. This won't screw up the IK.

 Unfortunately for me, I'll be making several different animations that all connect to each other, so that won't work for me. Oh well.