It’s Time to Get the Junk Miles Out of Your Marathon Training

Some people run simply for exercise. Some people run because they enjoy it. Then there are those runners who often transform from this into one who begins to train. At this point, your runs start having more of a purpose in terms of meeting a particular running goal you’ve set for yourself – such as a marathon. You’re proud of every mile you’re putting toward achieving your goal. And then you overhear someone talking about “junk” miles and you think…what does that even mean? How can someone ever refer to the hard work of running as junk?! It’s certainly a strange term with negative connotations. And no one wants to think their time and effort is going to waste as junk. As a runner who spends a lot of time focusing on my mileage quantity, I wanted to look into this “junk” mile belief and see if there is any truth to it.

So, what do people mean when they refer to runs as “junk miles” and is there really even such a thing? When a runner is in training mode, each run should serve a purpose. Even easy paced recovery runs help a runner achieve their goal. For a marathon runner, higher mileage does matter, but junk miles happen when a runner throws them into their training with no real reason for doing so. It can have negative effects. 

Let’s find out if any of the miles you are running really are “junk” miles and how to change your training to eliminate them. Because if they are, why in the world would you want to waste your time running them?

Who needs to worry about whether they’re running junk miles?

If you are a recreational runner who utilizes running to stay in shape or as a mental health benefit because it makes you happy, then you have no need to worry about junk miles. Neither do the runners who are in their off season and are just trying to maintain a base of weekly mileage. If this is you, keep doing your thing! All runners should have times in their lives where they are just enjoying the sport with zero agenda.

Those who need to listen in are endurance runners who are training for a specific race – especially when training for the marathon distance. Ultimately your goal is to finish your race in the time you have set for yourself. The purpose of your training runs is to help you achieve that goal. When you have a reason behind each training run and know how it’s helping you on this path, you are much more likely to achieve your goal.

Though running just to run can be beneficial for many reasons, you will benefit in your training much more by giving purpose to your runs. By doing this, you’ll ensure you’re not running any junk miles.

The Miles That Are Most Definitely Not Junk

So after much research, you’ve finally selected a plan for your marathon training. On it, you see words like “threshold, race pace, strides, tempo” and others. You’ll also notice the mileage building week by week. The coach who crafted the plan determined the importance of each of these types of runs. Obviously, you would hope that nothing would be put on your schedule that wouldn’t be necessary for you in succeeding your marathon goal. Just like when you were school, you hated when your teacher gave you “busy work” that you felt was unnecessary and not helping you get smarter or learn anything new. You wouldn’t be happy with your coach for doing this to you either.

So, which runs can you know for sure are helpful?

If you trust your coach, and hopefully you do (otherwise you need a new one), you can rest easy knowing that they have your best interest in mind. They wouldn’t require you to do any scheduled runs that they didn’t think benefited you in regard to your running goals. Even if you’re not working with a coach, you should be utilizing a plan with a proven track record that’s been useful for many runners in the past. Once you’ve chosen the plan – trust it. Do what it tells you to do. All the speedwork, all the hills, all the long runs…at the pace they say to.

Once you deviate from the plan…that’s when you might start running junk miles – miles that add no physiological value to your running performance. Or worse.

What Junk Miles Are and Why They’re Bad

Ok. So I said that junk miles are the ones that don’t really help you, but if they aren’t hurting you then who cares? Sometimes you just feel like getting out for a few miles to clear your head – not because your coach said so. These to me aren’t junk, but there IS a fine line.

The fine line is if you’re running them too fast.

How fast is too fast?

The golden rule of running is that approximately 80% of your miles should be run at an easy pace. This equates to around a 52 – 70% of your max heart rate. If you don’t feel like figuring this out, it’s about 2 minutes slower per mile than your 5k pace…or even slower if you want. I talk a lot more about this in my article Train Slower to Run a Faster Marathon, but the main take away is that in order to run a better marathon you need to run a lot of miles and you need to do so without hurting yourself. Running most of your miles at an easy pace ensures this. That leaves the other 20% for speed. The purpose for this speedwork is to build up strength and to develop your anaerobic system. You NEED this to get faster.

But when this works it’s way into your running that’s supposed to be easy, you get junk miles. This is why running that way isn’t a good idea.

1. You can hurt yourself.

Once you start deviating from your training plan and adding in randomly paced runs just because you want to, you risk hurting yourself. Did you know that mid-paced runs can put as much stress on your body as speedwork? And doing so without a purpose isn’t even making you a faster runner.

This doesn’t just include injuries that leave you unable to run at all. It can be any injury or discomfort that’s keeping you from performing your best. Achilles tendonitis, plantar fasciitis, and IT band pain are great examples of injuries you can probably run through but are going to slow you down. And running through these ultimately can put your running to a screeching halt. This is obviously not helping your goals in any way.

I think we can agree that hurting yourself because you didn’t have the self-control to reign in the speed per your plan is pretty junky. And boy is it hard – I am definitely guilty of this!

2. You’ll be chronically fatigued and you’ll sabotage your speedwork.

Even if you don’t feel any injuries creep up from running too many miles faster than you should, you might not be ready to hit your paces on your speedwork days. When your coach (or a tailored plan) gives you paces to run, it’s because they know what you’re capable of. If you’re rarely hitting your 800 m sprint paces, for example, it’s time to pay attention to your training. Have you been throwing in extra miles that weren’t on the agenda just to pad your weekly mileage? Or have you been running your easy runs at a pace faster than you should be because you got bored and wanted to mix it up? If so, this is the point that it’s safe to say you’ve been putting junk miles into your training.

As much as it’s so hard to trust that running so many of your runs slowly is actually making you a better runner, it’s true. All the experts say so. More isn’t always better.

But doesn’t higher mileage correlate to a faster marathon time?

If you’re like me, now is the time that you’re questioning everything you’ve read about higher mileage being an important factor in running a good marathon time. You’re thinking, “How can my miles be junk if they’re adding to my weekly mileage that’s ultimately giving me the necessary miles to run an entire 26.2 miles?”

Running a high amount of miles usually is very beneficial in preparing a marathon runner. In this article from Sports Illustrated, 2018 Boston Marathon winner Desi Linden talks about how she builds up to 100+ mileage weeks. And I highly doubt any of us would call any of her miles junk miles.

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Last year in my quest to qualify for Boston, my highest mileage week was 52 miles. I know that I’m capable of more – both higher mileage weeks and running a faster marathon. So the answer is, yes absolutely, running more can make you faster. But not when it’s at the expense of your body. When you add in miles without any purpose, especially that you run too fast, you are adding in junk miles to your workout.

The key is to build up mileage slowly over time. Once you’ve done so, you can still run high mileage without any junk miles by keeping that easy pace during 80% of your running.

Keeping the Junk Away From Your Marathon Training

Follow these steps to keep junk miles out of your marathon training – AKA the miles that are hurting your training.

  1. Stick to the prescribed mileage and types of runs your coach and/or plan gives you.
  2. Keep the easy runs easy. Don’t be tempted to go too fast for any reason.
  3. Sometimes a special run you want to do will deviate from your plan. An evening run with your kid, a weekend run with friends, or an extra jog to clear your head. No one wants you to lose your love of running by feeling like you need to skip these runs. So when you must, just keep them at an extra easy pace. This will ensure they aren’t giving your body extra fatigue. Anything that adds to mental wellness is certainly not junk.


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