Let’s start with some miles are good. If you’re going to be a runner the law of specificity dictates that you need to run to be a runner. Cycling, swimming, aerobics, weightlifting, playing tiddlywinks and rowing are all good but they do not exercise your neuromuscular system as a runner.
There are some thresholds in running that serve to clarify as well as confuse the issue. You make excellent gains in VO2max going from zero to about 25 miles per week and then again from 25 to 50 miles per week (about 16% gain each time). There is a dramatic drop off going from 50 to 70 miles per week (about 3% gain) and more than 70 miles per week (zero improvement). Here’s the rub. VO2max is not a good indicator of running performance. Bummer for mileage maniacs.
Running more than 20 miles per week yields a sharp rise in the incidence of injuries. The rate of injuries continues to rise from there as miles increase. Double bummer for mileage freaks.
These are the facts based on the last 40 or so years of research.
So, if you can run fewer miles and get the same or better race results and decrease opportunities for injuries, wouldn’t you? Unfortunately, so many runners pride themselves in the miles they run (I know, I’m at 51,300 and counting and I’ve done the 100 mile weeks before) it clouds their minds. It is one thing to run because you love it or because you use it for stress management. It is another to dupe oneself into thinking you are doing yourself more good by running more!