XCSkiForum.com

It's a question that's coming up finally on the WC scene! Couldn't come soon enough.

Well, I'm outta the loop. I gather it's because some dudes are DPing ENTIRE classic courses? So I'd think the answer would be to make them steeper. And to reduce subsequent flat sections.

...Or are some guys able to DP very steep climbs faster than the striders and not go under, do it as many times as a course might require, etc.

Hmmm, if a course were laid out to have twisty up's, maybe even switchbacks... In short, could features be added to discourage DP?

A few decades ago people used to cover most of the Vasaloppet course using diagonal technique.
I wonder how did double poling become the dominant technique on flat(ish) courses?
Was it just a sudden discovery "aha, double poling is faster than diagonal stride"?
Did the construction of the skis changed?
Different waxing?
Something else?

And on the subject of the course design to reduce the double-poling aberration. I recently watched on youtube all the XC races in 2010 Vancouver Olympics. There is very little double poling there, but the course, as you suggested, is mostly up and down, with a lot of twists and turns.
Fun to watch, unlike the double-poling races which resemble R2D2 rambling on skis.