I mean, I think I understand what they're saying. A thirty minute tempo will develop your aerobic capacity more than a thirty minute easy run-- more or less ana

I mean, I think I understand what they're saying. A thirty minute tempo will develop your aerobic capacity more than a thirty minute easy run-- more or less analogous to progressive overload in weightlifting. That's not to say that you can't grow/improve as a runner without challenging sessions, but I imagine the rate of improvement would be significantly lower. Pro runners would be doing as many workouts as possible per week if recovery weren't an issue!