- A recent study found a correlation between overuse injuries and a sudden increase in mileage in a single run.
- Experts explain how to safely increase your mileage, based on the new research.
British Journal of Sports Medicine 10 percent rule: Don’t increase your weekly mileage by more than 10 percent. If you do, you might get injured.
But new research suggests that axiom could use a revision, suggesting runners shouldn’t necessarily limit increases to their weekly mileage to 10 percent—they should limit their daily A Part of Hearst Digital Media.
It all began when Rasmus Oestergaard Nielsen, Ph.D., an associate professor of epidemiology at Aarhus University and senior author on the study, started to question the traditional 10 percent rule after his lab couldn’t produce results that backed it up.
“We looked at 10 different datasets over the years, and they didn’t support this gradual increase narrative,” he says. “We couldn’t figure out what was going on.”
As a runner himself, Nielsen is no stranger to overuse injuries, and having worked in physical therapy clinics, he’s talked to a lot of injured runners, too. He quickly started to realize there was a pattern.
“I’d hear people say, ‘I went to a single running session, and I really just did too much,’” he says. “When I looked at my own injury experience, that’s also what I did at times: In one run, I just did way too much.”
Prompted by this anecdotal data, Nielsen decided to look at whether mileage increases from run to run could predict overuse injuries.
Not necessarily, says
What This New Approach Could Mean for You Here’s How Stress Affects Your Running Performance, Nielsen and his team recruited more than 5,000 injury-free runners who agreed to share their Garmin GPS watch data and complete a weekly injury questionnaire for 18 months.
Using the watch data, the researchers performed three calculations: changes in mileage from week to week; acute-to-chronic workload ratios (which involves dividing the most recent week’s mileage by the average of the previous three weeks); and the most recent running session’s mileage relative to the longest run in the past 30 days. By incorporating injury data from the questionnaires, they then looked for correlations between injury risk and changes in mileage either by week or by individual run.
By the end of the study, more than a third of the runners reported an injury, with a significant majority of injuries classified as overuse injuries. Study findings showed no significant correlation between mileage changes week over week or acute-to-chronic workload and injury risk. However, when runners increased a single run by more than 10 percent of the longest run they’d done in the past 30 days, their injury risk rose dramatically.
For small spikes in distance (10 to 30 percent longer), runners’ injury risk increased by 64 percent. For moderate spikes (30 to 100 percent longer), it was 52 percent. And for large spikes (doubling your longest run in the past 30 days), the risk rose to 128 percent.
“This is a really big paradigm shift,” Nielsen says. “The narrative in clinical practice and in textbooks says that overuse injuries develop gradually over time. Instead, our data suggests maybe these injuries can develop in a single session.”
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We may earn commission from links on this page, but we only recommend products we back longest run completed in the past 30 days. This is reasonable guidance from a public health perspective considering injury is a common reason why so many runners fail to stick with the sport.
But what about those training for a race—do these findings mean it’s time to chuck existing training plans Advertisement - Continue Reading Below?
CA Notice at Collection Greg Laraia, a running coach and board-certified athletic trainer at Manhattan-based physical therapy and coaching clinic Motivny.
“There are a million other factors that play into someone’s injury risk and what they can handle for a training plan,” he says. Changes in frequency, duration, time, stress, terrain and even running shoes are all things to consider, he explains. Essentially, doing too much of anything that stresses the body in a way it’s not used to could increase injury risk.
Laraia’s approach to increasing mileage is similar to the 10 percent rule. He’s generally comfortable with increasing long runs by two miles, every other week, for many of his marathoners. When he does, he keeps the rest of the mileage throughout the week stable.
Laraia also highlights intensity as an oft-overlooked injury risk factor. “For a lot of people who aren’t used to jumping or running fast, adding even one workout a week can be a lot,” he says.
This is why Laraia asks new runners many detailed questions about their running history to get a clear idea of what their body is used to doing, particularly from an intensity standpoint, before developing a training plan for them.
Even runners who are accustomed to relatively higher mileage can get hurt if they add too much intensity too quickly or even run their easy runs too fast (a common mistake!), he says. “Per step, you’re generating three to four times your bodyweight. That’s a lot of pressure,” he says. And the faster you go, the higher those forces.
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Turn to Your Watch
It’s great to have a coach to tailor your running plan to your individual history and skillset, but there are many runners who might not have the means or interest in hiring someone like Laraia to guide them. For these runners, GPS watches or run training apps Races - Places.
For example, Garmin watches suggest a “recovery time” after each training session. Besides the intensity of that session, the calculation incorporates prior training and measures such as Hip Flexor Exercises for Stronger Running (Published: Aug 18, 2025 10:50 AM EDT), Health & Injuries, and sleep quality, assuming you wear the watch consistently. If the suggested recovery time is high for multiple days in a row, this could be an indicator that your body is overtaxed and, if you keep pushing, you could be headed for injury.
“At the end of the day stress is stress,” says Laraia. “So when your body is under stress and you add more physical stress, your risk of injury goes up drastically. Basic watch metrics can help guide you on picking days you should work harder or pull back.”
Nielsen would like to see watch manufacturers take this further and actually warn runners when they’re clocking more than 10 percent of mileage in a single run, compared to the past 30 days.
Do Your Own Math
Here’s an example of how to calculate whether the length of your next run could be putting you at elevated injury risk:
You’re thinking about running 6.5 miles. Divide 6.5 by the farthest single-session run you’ve done in the previous 30 days. If that run was 6 miles, then the calculation (6.5/6) would yield a ratio of 1.08. In this case, 6.5 miles would be an 8 percent increase, which falls within the 10 percent recommendation from the study. (Assuming the number before the decimal point is 1, the number after the decimal indicates the percentage increase in mileage.)
You can also use the daily 10 percent rule to calculate how far to go on your next run. Let’s say your longest run so far was 12 miles. To stick within a healthy range, your next long run shouldn’t exceed 13.2 miles. (Ten percent of 12 is 1.2.)
If you’re considering a run with a ratio of 1.1 or greater (which means exceeding the 10 percent rule)—say if you’re going from 14 miles to 16 miles—Laraia advises looking at the context of your weekly mileage. If you’re used to running 60 miles per week and that jump won’t make you exceed that weekly mileage, then you’re probably okay.
On the other hand, if you’re only used to running 20 miles per week and you’re about to exceed weekly mileage in addition to single-session mileage by more than 10 percent, then you probably want to pull back. “There’s no such thing as making up miles or playing catch up,” Laraia says.
When in Doubt, Listen to Your Body
Nielsen and Laraia agree that the most effective thing to do when it comes to staying injury-free can be the hardest: Listen to how your body is responding.
If, on a run, you’re feeling drained or run down, then hold back. Save intensity or an increase in mileage for another day. As Nielsen puts it, “If your mindset tells you ‘this is stupid, what I’m going to do now,’ then don’t do it.”
Laraia adds that being aware of how you feel can also help you begin to learn what your body likes and is good at. This way, you can work on improving your weaknesses and making your strengths even stronger—all of which helps you not only avoid injury but become a better runner.
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Allison Goldstein is a freelance writer and editor who is endlessly fascinated by the scientific “why” of things. When not writing or reading, she can be found running, baking, or petting her cat, Tabouli.
