Runner's Knees

I came across this post today with Hal Higdon as the author. I'm a fan of his and used some of his program when I trained for my first marathon. I'm curious to find out where 55 miles came from and also why Hal, who ran more than 100 miles per week many years ago has now downsized his recommended weekly mileage? It may be that at his age that's all he feels like doing or he's not training for a marathon and doesn't need the additional mileage.

Are runners' knees worse off than non-runners'?

"The stress of impact causes the joint to adapt positively, thereby improving its overall health," writes Barker. "There is, however, a threshold that if surpassed exceeds the normal wear and tear a joint can endure."

Determining a level of safe exercise, however, puzzles researchers. One study quoted by Barker suggests 55 weekly miles as the point where joint breakdown begins, but only a small percentage of runners train that much, even when getting ready for a marathon.

Hal Higdon
For Active.com