Busting the Myth of “Junk Miles”

Published February 23, 2023 11:41AM

Rewind the clock to early September, 2001. I was a senior in high school and my cross country team had just hosted our first meet of the year. I was finishing a cool-down after the race with a few teammates.

As we stretched and recounted war stories from the race, the indoor track coach walked past us into the fieldhouse. He asked us how much mileage we had run after the race, to which we replied: “Four miles.”

“Junk miles!” he scoffed, apparently letting us know what he thought of our 30-minute cool-down. Little did he know, I had been trying to run as many of those alleged “junk miles” as I could for the previous three months. Also, I had just won my first cross country race ever.

Today, I often think back to this moment and wonder what would have happened if I had listened to that coach. Because, truthfully, I ignored him.

In the following few years, one of my top training goals was to dramatically increase my weekly mileage from about 30 miles per week in high school, to averaging over 60 as a freshman in college. Soon, I was regularly running 80-plus miles per week.

Were these wasted miles? Was my effort unnecessary for my goals? Could I have run less, but raced faster?

What Are Junk Miles?

“Junk miles” is typically a pejorative term to describe wasteful running that won’t help you reach your goals. Instead of mileage that’s strategically structured to increase fitness, junk miles are what some coaches consider extra miles that will just leave you more tired with an increased injury risk.

Often, runners and coaches who subscribe to a low-mileage, high-intensity training program believe that junk miles are real. If a run isn’t a workout, there’s very little place for it in their training program.

Conversely, high-mileage runners love extra miles and don’t consider them as junk or wasteful. They believe that more running is better, within reason, and that volume will ultimately lead to faster race times. For high-mileage runners, all miles have a purpose, even if they’re “extra” or are done at an easy or moderate effort. That purpose is aerobic development.

Are Junk Miles Real?

Most runners, especially new runners or low-mileage runners, are most limited by their aerobic fitness. Basically, what holds them back the most is a lack of endurance. And the best way to build this general endurance is to run a lot of easy miles.

But endurance isn’t the only physical skill being developed by a ton of easy running. Easy runs also contribute to muscular-structural development. In other words, your muscles and connective tissues are toughened by repeatedly running at an easy effort. After all, you must be able to run easy before you can run fast. Without a foundation of easy (“junk”) miles, the body won’t be aerobically or structurally ready to handle the demands of racing or high-intensity workouts down the road.

We can also look beyond the physiological benefits of easy running to what elite athletes are doing out in the real world. Most pro athletes, especially those who compete in long-course races like the marathon and beyond, train under a high mileage program that often sees mileage levels in excess of 100 miles per week (and a vast majority—likely 80 percent or more—is at an easy effort). Pro Jakob Ingebrigtsen, for example, won the 1500m at the 2020 Olympics and, even as a middle-distance runner, regularly runs over 100 miles per week.

And that’s not just for elite athletes. In 2017, Strava looked at the training data of 30,000-plus marathoners. They discovered that men who ran Boston Marathon qualifying times ran about twice as many miles as men who did not qualify. The results are also similar for women.

In a previous article, we learned the difference between “capacity workouts” versus “utilization workouts.” Those additional miles that some coaches consider “junk” miles are in the capacity-building category of workouts. Done consistently over time, they will undoubtedly increase your capacity for more training.

In summary, the physiology and real-world results of both elite and recreational runners clearly demonstrate that more running is usually a good thing.

And Now, For Some Caveats

Of course, additional mileage can also become burdensome. It’s not as simple as saying, “more is better.”

Some volume loads are simply too high, no matter who you are. There are very few runners who can manage 130-plus miles per week, even the most talented and economical elite athletes. At this point, concerns about injuries, hormonal stress, and fatigue become more important than the benefits of more aerobic development. While there are outliers—elite athletes who run monster mileage levels of 130+—it’s rare and those athletes usually struggle to maintain that volume in the long-term.

And of course, recreational runners without the support of a sponsor and a wide open schedule may struggle with lower volumes of 70-80 miles per week. “High” mileage is relative.

Most often, the problem runners experience with higher mileage levels is the multiyear journey to those levels. In other words, it’s the rate of increase that’s the problem. Beware of the “Three Too’s” that often lead to overtraining or injury: too much mileage, too fast, too soon.

Easy mileage must also be truly easy, especially when that volume is growing. Beware of too much Zone 3 running, which famed coach Jack Daniels might call “grey zone training.” When you’re building mileage, keep those miles easy (Zone 1 or 2 or a perceived effort of 3-5 on a 10-point scale).

All mileage increases should be gradual and occur not just over weeks, but over months and years. Learning how to run high mileage is a methodical and patient process! When in doubt, slow down and run less, to keep yourself healthy.

How to Plan Junk Miles

Now that we understand that more mileage is usually better, if done safely, how do we go about running more easy miles? We can start by determining what mileage level you’re comfortable with right now. Look over your training journal to determine a mileage range that feels easy and that isn’t too physically or mentally stressful. That’s your baseline mileage.

When you’re building mileage up to your baseline, you can be more aggressive than the classic “10 Percent Rule” (which says to only increase your mileage by 10 percent per week). This volume is easy, after all. But as soon as you reach your baseline mileage, we must be more conservative. Beyond this level, we’re reaching into uncomfortable territory that’s more stressful to your body, your mind and your weekly schedule. Now, it’s more effective to increase mileage by 5 to 10 percent every one to two weeks instead.

It can also be helpful to add in a recovery week, where volume decreases by 10-25 percent every three to six weeks. This nuanced approach helps runners better build mileage in a safe way that minimizes injury risk. Over time, the peak mileage from season to season can increase by 5-10 percent, helping you consistently reach higher and higher volumes over the years.

The Bottom Line

The next time someone scoffs at your running volume full of “junk miles,” you can rest easy knowing that you’re following in the footsteps of elite runners, Boston Marathon qualifiers, and the fundamentals of exercise physiology. Keep those miles truly easy, build gradually, include other intentional workouts, and you’ll thrive in the long run.