It may be possible, however, to get the fitness and durability benefits of running more miles without increasing your injury risk as much as high mileage does for the typical runner. Just follow these three guidelines:
Guideline No.1: Ramp Up Slowly
As the physical stress theory shows, whether an increase in physical stress makes a tissue stronger or breaks it down is determined by the magnitude of that increase. In running, that translates into the rate at which you increase your weekly mileage.
By ramping up very slowly—the often-cited rule is 10 percent per week—you expose your leg tissues to manageable amounts of damage that they can repair and adapt to before the next time you run. When your tissues are given the opportunity to fully restore their prior homeostasis between runs, then you can't get injured—by definition—because an injury is a loss of homeostasis.
Guideline No.2: Obey Your Pain
No numerical rule can predict how your body will respond to your training. While in the long run using the 10-percent rule will certainly keep you healthier than you would be if you included abrupt mileage spikes in your training, it still doesn't make any sense to continue increasing your running mileage at a rate of 10 percent per week if you've developed a sore spot that gets a little worse every time you run.
You must never ignore pain.
When you develop a sore spot, reduce your running just enough to make the pain go away and then begin increasing your mileage cautiously. Sometimes it's necessary to stop running completely for a few days, but that is more than worth it when you consider that the possible consequences of ignoring the pain and continuing to run might be many weeks off with a far more serious injury later.
Guideline No.3: Be Consistent
Research suggests that injuries are more likely to occur during periods of increasing running mileage than they are during periods of steady mileage, even if that steady mileage level is high.
According to the physical stress model, simple repetition of a familiar stress is unlikely to cause a loss of homeostasis, and in running that means that you're unlikely to break down by maintaining your mileage at a consistently high level once you've safely brought it up to a high level initially.
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Naturally, "high mileage" is relative. As a general rule, avoid letting your weekly mileage dip below 50 percent of your peak weekly mileage. So if your heaviest training week during the year is 50 miles, try to avoid running fewer than 25 miles at any other time of the year, except perhaps during a brief (one- or two-week) off-season break.race.
This article is adapted from The Runner's Body, by Ross Tucker, PhD, Jonathan Dugas, PhD, and Matt Fitzgerald (Rodale, 2009).