Reply To: Aerobic Threshold in long duration activities May 31, 2024 at 5:00 pm #134852 Scott JohnstonKeymaster Ralf: If the goal is to improve your aerobic capacity/elevate your AeT then you need to train below your AeT. The drift test tells you whether the STARTING heart rate was at or below your AeT. Your AeT does not drift up during a long ski tour. Scott