Out of cursiosity, why does cross country skiing burn significantly more calories than freestyle? Is it because more of the muscles are in play during a cross country 'trip'?
You can ski down a mountain using very few of your muscles and energy however to keep moving doing cross country you really need to use your muscles rather then gravity.
I know when I did it, i was exhausted once I was done. It takes alot out of you but when it comes to freestlye there is no comparison because honestly freestlye doesn't take as long as cross country does.