How many miles is too much for running ?

If somebody who doesn't run and hasn't trained properly goes out and forces their way through a marathon the chances are they will injure themselves.

However if you train correctly and slowly build up you mileage base you can run long distances with no problems. Your body will adapt to the miles and you will become stronger and you will have great endurance. Once you're running 50 plus miles a week it becomes really easy, you start to feel like shit when you don't run. Phone Post 3.0

100miles is too much.
50miles regular is fine.
Consistency trumps intensity in the world of injury prevention Phone Post 3.0