I think the oft missed bit about zone 2 is that the goal is to increase volume. If you simply reduce intensity without increasing volume, you'll get worse, not better.
If you only run 30 minutes once a week, you won't see as many gains if you do it in zone 2 than zone 3/4. But you also can't run 10h/w zone 4/5, so that's where the zone 2 comes into play. It allows to increase volume without increasing fatigue/risk of injury too much.
If you only run 30 minutes once a week, you won't see as many gains if you do it in zone 2 than zone 3/4. But you also can't run 10h/w zone 4/5, so that's where the zone 2 comes into play. It allows to increase volume without increasing fatigue/risk of injury too much.