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How to Build Up Mileage Safely this Summer

With long days at our disposal and limited options for cross-training, there has never been a better time to lean into running.

couple running together on empty city street during workout at sunrise
Thomas BarwickGetty Images

If you ran cross-country growing up, you’re probably familiar with summer base training. It looks something like this: For about three months, give or take, from the beginning of June until the end of August, your weeks consist of easy to moderate-effort base runs that gradually increase in length over time. The aim of this type of training is not to make you faster, per se, but to build your endurance, strength, and running efficiency, so that when races resume, you have a solid foundation on which you can sharpen your speed.

Obviously, summer this year will look different from past seasons. Because of coronavirus restrictions, many of the activities we usually do during the warmer months (think: racing, traveling, and visiting pools and gyms) might be prohibited, depending on where you live. Fortunately, the closures and cancellations don’t impact one activity: building a solid mileage base. In fact, having more time at home and fewer obligations on your calendar will likely make it even easier to pour more of your energy into running.

Whether you’re training for a race later this year or you simply want to raise your ceiling for years to come, now is the perfect time to build a strong foundation. Without races on the horizon for the next several weeks, you have a relatively risk-free window to experiment with higher mileage without worrying about speedwork or tapering. As Runner’s World has written about before, the benefits of running higher mileage are clear: building up your mileage (to a point) forces your body to adapt on its physiological, biochemical, and molecular levels, which in turn makes you a much more efficient and faster runner. Hello, new PR.

But as anyone who’s suffered an overuse injury knows, there’s a right and wrong way to build mileage. Here, Runner’s World asked Stephen Furst, a former All-American runner at North Carolina State University and current coach at the sub-elite all-women’s team Raleigh Distance Project, to share a few tips for how to increase mileage safely this summer.

Follow the 10- to 15-Percent Rule

Many overuse injuries happen because runners increase mileage too quickly, Furst explained. New runners who ramp up volume too fast are especially vulnerable to injuries, because their bones, tendons, ligaments, and muscles haven’t yet been conditioned to withstand the impact of running. But even seasoned runners can get hurt from building too quickly.

“I’ve seen runners who used to do 100 miles per week get hurt while they are only at 60 per week, because they built up incorrectly,” Furst said. “Just because you used to do a certain amount of miles doesn’t mean you can pick up right where you left off.”

That said, runners who have run higher mileage in the past can usually increase their mileage more rapidly than those who haven’t, since their bodies have already adapted to high-volume training at one time, Furst explained.

Regardless of your previous experience with mileage, all runners should follow the 10- to 15-percent rule: Calculate what 10 to 15 percent of your goal weekly mileage is, then increase your mileage each week by no more than that amount. For example, if your goal is to run 60 miles per week, you should increase your mileage each week by no more than six to nine miles. If you usually run 10 miles per week, increase by no more than 1 to 1.5 miles the following week.

Build for Three Weeks, Rest for a Week

Another key to building mileage safely is to give your body a “down week.” In the same way that you shouldn’t run hard every day, you shouldn’t try to up your mileage every week. Furst recommends increasing mileage for three weeks, and then taking the fourth week “down,” by running a lower weekly mileage and more easier runs than the week before.

For example, if you aim to run 60-mile weeks, you may run weeks of 40 miles, 46 miles, and 52 miles, and then drop back down to 46 miles in the fourth week. This relative resting period gives your legs time to absorb the mileage and build critical muscle memory before tacking on more miles.

“Developing and maintaining consistency in your running is really important,” Furst said. “Any type of change on the body—including mileage—is really stressful, which is why so many injuries happen during buildup phases. Once your body is comfortable in a certain mileage, it is very easy to keep doing that week after week.”

Increase Your Long Run Gradually, Too

Because many recreational runners who are training for marathons do the bulk of their weekly mileage in a weekly long run, it can be tempting to increase mileage by simply ramping up long runs. But this method can be especially hazardous, since extending time on your feet while you’re already tired can result in sloppy form and leave you more prone to injuries.

Furst recommends that runners increase long runs by 10- to 15-percent each week, with a down week every fourth week, in the same way that you increase your overall mileage. For the runner who is building to 60-mile weeks with a peak long run of 20 miles, the four-week pattern could look like this:

  • 40 miles (10-mile long run)
  • 46 miles (12-mile long run)
  • 52 miles (14-mile long run)
  • 46 miles (12-mile long run)

    Take It Easy

    While you’re building mileage, your focus should be on completing the distance, not hitting a certain pace. A common mistake runners make is increasing both volume and intensity at the same time, which can lead to overuse injuries or burnout, Furst said. Speedwork is especially ill-advised while running in the heat, because your body is already working harder to maintain a given pace. Leave intervals for later this year, when the weather is cooler and you’re preparing to race again.

    Prioritize Fueling and Recovery

    Hands down, the best way to successfully build mileage is to recover well. “In my experience, runners usually aren’t overtrained, but under-recovered. A lot of runners blame their failure on being overtrained when really they just had a bad day,” Furst said.

    While most runners think of recovery as what immediately happens after a workout—cooling down, stretching, and foam rolling—it involves much more than that. Getting a proper amount of sleep, eating the right foods and enough of them, strength training regularly, practicing mindfulness, and eliminating extra stress are all necessary components of recovery.

    Sleep and fueling enormously impact athletes’ training performance, Furst said. Runners often misinterpret signs of sleep deprivation as training fatigue, which can lead to running less when you really just need more sleep. While Furst’s runners usually have jam-packed work, travel, and social schedules, the coronavirus restrictions have eliminated many of those obligations, allowing them to get more sleep each night.

    “They’re getting around 8.5 hours of sleep per night, which is more than they have in 10 years,” Furst said. And it’s paid off in practice: “Their fitness levels are great, even though the training environment is not optimal.”

    Fueling properly is important for any training cycle, but it’s especially critical when you’re increasing mileage, because you have to consume more calories to keep up with the extra energy you’re burning each week. Keep in mind that while counting calories can be helpful in ensuring you get enough food, you shouldn’t stress about it.

    For runners, eating more—especially whole grains, produce, and healthy proteins and fats—is always better than eating less, because it ensures that your body has plenty of energy and nutrients to rebuild bones and muscles. And don’t be surprised if you gain a little weight when you’re building mileage. Furst said that he often gains a few pounds during a buildup, but once his body becomes comfortable with the mileage, his normal appetite returns again, and he sheds the extra pounds.

    Look Out for Injury Warning Signs

    Even if you do everything right while building mileage, injuries sometimes happen. That’s just the nature of our high-impact sport. While overtraining is unlikely to happen if you increase volume slowly and prioritize recovery, if you feel extremely fatigued while running for seven days in a row, you should probably take a few days off, Furst said.

    Continuing to run on exhausted or achy legs can make you more at risk for developing overuse injuries. If you do develop an injury that changes the way you run and alters your gait mechanics, you should have it checked out by a doctor.

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