Sorry If I was a bit unclear, I half of my point was about the ability to have good dorsiflexion. As in being mobile enough to have enough dorsiflexion(and how much is enough as in angle.).
Here is poster jmf communicating what I’m getting at more efficiently.
"Coming down from the 800m to the 400m I’m trying to learn how to really sprint. One thing I’m wondering is if inflexibility around the ankle - as in I can’t squat low without a heap of plates under my heels- is a barrier to running fast. If so, which stretch/exercise would best fix this? "