[Bjorn]

Those with greater knowledge might correct me, but as far as I understand your aerobic capacity is defined by the local muscles used in the activity of interest and not by the heart. The heart rate (and HR drift) is simply an effect of the work performed by the local muscles. Consequently, the aerobic capacity – and therefore HR drift and HR zones differs between different sports/activities. For myself, my aerobic capacity (upper Z2 HR ) is 137 bpm in running, 132 bpm in uphill walking on treadmill and 122 bpm on a bike.

Again, someone may correct me, but if you would like to improve the skiing I think you should be careful in doing what may be Z3 in skiing – since the accumulation of fatigue will have a negative effect on the technique. Better to go easier with good technique on longer sessions, and complement with shorter intervals and more like ME training to build strength.