Overspeed has been attempted in a variety of ways and to different degrees. I have always used tailwind (Cheap and plentiful at York U) as an overspeed method and the contrast there is done by either modifying subsequent sessions to sub-max or running into a headwind if you fear the athlete will get carried away or the weather isn’t cooperating. (Tailwind stretches out the stride while a headwind shortens it).
The East Germans used altitude training for this effect for sprinters in Mexico City for years but the longer duration of their training camps meant sufficient exposure to “local conditions” that food poisoning often undid any benefit.