When working, keeping warm doesn't use additional calories to the work (skiing and sled-pulling), since heat is a biproduct of the work. In fact they are carefu

When working, keeping warm doesn't use additional calories to the work (skiing and sled-pulling), since heat is a biproduct of the work. In fact they are careful not to work too hard so they don't sweat. (Getting wet makes their insulation ineffective, so is very dangerous.)