4 days in not enough time for any kind of altitude acclimatisation. In fact, your body's response to higher altitude decreases the first 10 to 14 days before full acclimatisation at around 3 weeks. I think your ride was mental/motivationally enhanced by the excitement of riding in a new and cool place.
Last edited by BikeWNC; 12-09-04 at 03:14 PM.