The usual scenario of progressive injury is:

  1. "Gee, my foot, leg, etc is sore. Couldn't have been the running I did this morning".

  2. "Hmmm, when I'm running it feels kind of tight where it was sore yesterday".

  3. "Wow, that was tight yesterday too, maybe I'll run fewer miles tomorrow".

  4. "Well, it's still sore, I'll go run on it to see if it still hurts".

  5. "Ouch! Better not run on this, it might cause permanent damage"

This seems to be how I've managed to knacker my left leg.