Some of the more rudimentary guides I've read say to avoid rocking in the saddle. Some pedaling efficiency guides also suggest keeping your butt in one place.
How is it then that when a pro is observed from behind, you see a lot of rocking and "snaking", an alternating contraction of the sides of the back? Dave Zabriskie is textbook for this in his TTs. I've only heard this simply explained by, "Oh, you'll see more of that from pros during climbs, sprints and time trials."
What's your feeling on this? It seems that these riders are deriving more power from the technique in a way that might raise work output at sub-lactate threshold.
It also appears that distributing work load to more muscle groups might reduce lactate production.