A recent article in the Florida Times-Union explained how high mileage can lead to injuries that sideline runners and cause long-term problems. According to the article, “[c]ross-training with cycling, swimming or weights can help avoid injury. ‘It’s actually tricking the body. That might be a way of resting, rather than taking a lot of time off,’ said [Nigel] Sparks, the 1992 Big Ten soccer player of the year at Penn State” [and an assistant professor at the University of Florida’s Bone and Joint Center at Emerson].
The key is to avoid these injuries though creative, purposeful training, as described in Smart Marathon Training.
Read more at http://jacksonville.com/sports/local-sports/local-running/2012-03-03/story/runners-which-bigger-speed-bump-age-or-mileage#ixzz1oYmUiMSV
High mileage can lead to overuse injuries, but neither doctor deters runners from training and competing often, if they do it smartly.