Being born in Sweden, Willow has always had a good level of endurance just from living where she did. The standard hockey training regime got her super far, but she also was training at high elevation which helps your body pump more blood meaning you can go for longer, and I think training in extreme cold kind of does the same thing because you need more blood to be warm. Regardless, it works for her and it’s a reason why she’s so good for the course of the entire game. The other method she uses is the new resistance training exercise bike her trainer recommended to her. It automatically starts at the max resistance and you can only make it go up and up so you’ll be trying to bike your way through some tar and quicksand all at once. If that doesn’t make your lungs build up the greatest stamina of all time I don’t know what will.