Originally Posted by
OBoile
This is only true if you're running some very high mileage. For most people, including cyclists doing it as cross training, it's fine and may even have a protective effect.
There can also be the problem of continuing to run the same mileage after marrying and establishing a career and putting on weight, as so many do. Cyclists can get away with putting on weight. So can runners, but only to a point.