Good point, and easy to explain. The two Yuri's were moving down hill with the he group initially. It was a very simple survival strategy ,one we all would of thought of. The Two Yuri's foot prints were covered by the snow at the lower elevation when they decided to run ahead.
Why do I know this, because the group actually made it to the forest at a faster pace when at the lower elevation. They were suffering the terrible effects of frost bite by now.
How fast can someone run under those conditions. I know from personal experience fast as hell.
On vacation when I was 12 years old the family was next to a river with some very cool rapids. The rocks on the bottom were slimy and slippery so you couldn't even stand on the edge without busting your head open.
I was exploring downstream when my younger sister was being dragged down the rapids. As fast as lightning I was dialed in and was flying across those slippery rocks like they were not there I had her out in no time.How could I do that? because of Adrenaline.
Zina and Luda were on the minds and the Two Yuri's had no problem running down to the forest...