Coaching

The Science-Proven Way to Dial Up Your Mileage

Want to run farther and faster? Try the acute-to-chronic workload ratio (it’s much simpler than it sounds) to help avoid injury.

Last updated: December 23, 2020

When you’re making running part of your lifestyle, slow and steady really does win the race.

How to Increase Your Running Mileage Safely

“One of the biggest mistakes runners make is increasing their mileage or frequency too quickly, to the point that they get injured from a combination of overuse and weakness,” says Steven Mayer, MD, a sports medicine physician at the Northwestern Medicine Regional Medical Group, in Illinois. That’s why running coaches have traditionally recommended the 10-percent rule, or the idea that you shouldn’t advance your distance or pace by more than 10 percent each week.

Running is a high-impact activity; your muscles, joints, bones and connective tissue can take a beating from hitting the pavement as you carry your entire body weight on one leg at a time, over and over. If you start running every day or suddenly double your distance before your tissue has adapted and strengthened to handle the impact, it can start to break down, says Tim Gabbett, PhD, a physiologist and applied-sport scientist at Gabbett Performance Solutions in Brisbane, Australia.

You might not even notice when that breakdown starts. Your cardio fitness (heart and lung capacity) progresses faster than your muscles can keep up with, says Mayer. That means you might think you’re conditioned to turn a few 3-mile runs into 5-milers on the spot, then suffer through shin splints or an achy hamstring later. In that way, running can make it all too easy to chase lofty goals one week, then be shuttled to the sidelines the next.

If you start running every day or suddenly double your distance before your tissue has adapted and strengthened to handle the impact, it can start to break down.

Tim Gabbett, PhD, Physiologist and Applied-Sport Scientist at Gabbett Performance Solutions

How to Increase Your Running Mileage Safely

Forget the Old Runner’s Tale

That’s not to say you shouldn’t try to go farther or faster or run more frequently. After all, nothing sounds more boring that running the same 5K loop three days a week until the end of time. The key, says Gabbett, is to push yourself little by little, exposing yourself to more stress, or load, safely.

While following a guideline for progression is a good idea, the 10-percent rule actually has no scientific basis, and “it’s not necessarily proven to prevent injuries,” says Mayer. In fact, runners who increased their training load by up to 50 percent per week experienced almost the exact same injury rates as runners who followed the 10-percent rule did, according to one study from the University of Groningen in the Netherlands. And novice runners who averaged 20 to 25 percent weekly increases avoided injuries in a study at Aarhus University in Denmark.

Plus, the 10-percent rule doesn’t take into account context or fitness history. If you’re a workhorse athlete already logging 100 miles a week, adding 10 percent (or another 10 miles) to your training load might feel near impossible. On the flip side, if you’ve only ever run 1 kilometer, it would take you nearly 16 months to reach a marathon distance. While that’s totally fine, it may be a way longer time commitment than is necessary or sustainable.

A Personalized Way to Advance

To figure out how to move forward, Gabbett recommends using a more individualized guideline he employs for his athletes: the acute-to-chronic workload ratio. It may not roll off the tongue as easily, but in practice, it’s actually quite simple. “It takes into account how much you ran this week [the acute] versus how much you ran over the past four weeks [the chronic],” he explains. (If you haven’t logged four weeks yet, stick with what feels like a relatively easy amount of mileage for your first month of running to get a foundation under your belt, then use this ratio over and over to keep adding on.)

“It’s a feedback cycle,” says Gabbett. Every time you add to your load via weekly distance or speed, check in on how you’re feeling immediately afterward (“I crushed those hills”) and within 48 hours (“My legs are so sore”). Based on both, you should have enough info to decide whether to dial it up or spend extra time on recovery, he says.

For example, if you’ve been running 10 miles a week for the past few weeks and did 15 miles this week, that load is 1.5 times greater. If it felt hard or bad, you may want to spend another week at 15 miles or even scale back to 10. But if it felt good, you can try increasing your mileage by that same rate next week. Even if you felt incredible, it might be best to stick with the 1.5 increase: Research shows that an acute-to-chronic workload ratio within 0.8 to 1.3 was associated with a low injury risk, but that injury risk increased significantly when the ratio was above 1.5.

One other crucial tool to help keep you happily running along: Strength training. Focusing your resistance routine around glute and core work specifically, research suggests, could help stave off some common overuse injuries, as it bolsters your bones, tendons and muscles to better handle all that stress, says Mayer. Try running every other day and working on strength (and, of course, recovery) in between.

Slow and steady might not sound sexy, but becoming a healthy runner for life? That has a nice ring to it.

Words: Ashley Mateo
Illustration: Ryan Johnson

How to Increase Your Running Mileage Safely

Take It Further

For more expert-backed guidance on mindset, as well as movement, nutrition, recovery and sleep, check out the Nike Training Club app.

How to Increase Your Running Mileage Safely

Take It Further

For more expert-backed guidance on mindset, as well as movement, nutrition, recovery and sleep, check out the Nike Training Club app.

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