I live in a state where there is a lot of snow in the winter so around half of the cross country kids join Nordic, and the other half does winter running. To get in shape for track I will say winter running can’t compare to Nordic. Here in Minnesota the running trails are plowed and easy to run on, so winter trading is full of aerobic endurance building. Nordic is different, is a lot less muscle impact and upper body as well. I’ve seen the heart rates not go above 140 in a Nordic race. My opinion is winter running will drastically help you get in shape faster compared to doing Nordic cross country skiing in the winter. I don’t know a lot but if someone can give some insight, feel free to reply