Thanks for your answers, my goal is personal, I don’t have any competition in mind, but I would like to run some small 20-30 km trail with 2/3000 meters of altitude difference in our mountains (Apuan Alps). I understand that workouts where I go too far in zone 3 are not very productive, but staying in zone 2 is really a fight! I can do it well when I train on a flat level, but on routes with elevation gain it is much more difficult … But from the answers received I understand that to improve the aerobic base I still have to prefer these routes with elevation gain, since my goal is to do trail in the mountains. In general I try to train 3 to 5 times a week, always staying over an hour.
Thanks again to everyone, happy Easter,