Great thread and although I think we may have had this discussion somewhere on here before here are my thoughts…
These types of workouts may cause structural adaptations in the lower limbs given the nature of the runs. General/Semi specific endurance of the “body” primarily the legs over longer distances would be the adaptation. At the same time energy system adaptation would occur since when we are working the energy systems it is a partial muscle group(s) being worked which control which energy system we are using. At the same time research shows us there is a crossover/bleeding of one energy system to the next which means when we are working the oxidative/gylcolytic system(s) we are also including the ATP-CP System which would explain how it may have a positive effect on short sprint times more specifically the 100 meters.