I am with hflam, use IK to place the feet or hands, but then select parent body parts, legs for the feet, arms for hands, etc. and SET a keyframe there.  Once IK is turned back off body elements tend to shift a bit too, and slight adjustments are often required.

I tend to avoid adding BODY keyframes so I can later adjust THAT element in the scene file, but it is important to add keyframes to the parent elements, and it's true setting a whole body keyframe would work.

Mostly it takes time and a whole lot of work to create an animated sequence.

Best Wishes,
Rªnce