Is junk mileage making you slower?
Before we answer that question, let’s figure something else out.
What exactly is junk mileage?
Seems simple enough, but a quick Google search and a few clicks yield no less than four distinct definitions:
1. Easy, recovery miles.
2. Recovery miles that are done too fast.
3. Too many recovery miles.
4. Any miles that can’t be classified as recovery, tempo, or interval pace.
Wow! With four, maybe more, definitions floating around, is it any wonder junk miles are the subject of so much disagreement?
Ok, so we can’t precisely define “junk,” but maybe we don’t need to. Let’s throw out definition #4, since it doesn’t jive with the others, and just ask the question, “How can any ‘easy’ running be bad?”
The answer to this one is clearer: Easy running, also called recovery running, is counterproductive when it negatively impacts the next day’s workout. Often we don’t know that we’re running too fast on what are supposed to be slow days. And when we run long, slow distance, it’s tempting to count that mileage as recovery mileage, in the interest of fitting an extra speed workout into the week.
Though not everyone agrees, most of us would concede that if your easy run causes you to miss your paces during the next day’s speed workout, you overdid it a little bit. Still, that might not be such a bad thing. As pointed out in a Running Times article on the subject, there’s a tradeoff between running volume and training stress, both of which benefit us. Faster workouts provide the stress; running easy in between them contributes added volume. So if you push the easy mileage one day and your speedwork suffers, all is not lost. You simply weighted the scale toward volume that week. Ever have such a tough track workout that you felt compelled to take the next day off, thus decreasing weekly mileage for the week? I know I have. Yet, strangely, nobody calls that additional effort on the track “junk.”
The point is that we need both speed workouts and easy runs. Neither is junk; they both serve a purpose. Speed, or stress, causes us to get stronger by increasing our VO2 max. Easy mileage, or volume, trains our brain to build pathways that make running more efficient. (It doesn’t, studies show, actually do anything to help with recovery. Rest does that.)
But if we need both of these things, can’t we just blend them together into a single, moderate-paced style of run, the perfect balance between difficulty and distance? Fortunately, no. (That’d get a little boring, wouldn’t it?) As speed workouts get slower and easy runs get faster, they lose their respective yin and yang. On a longer time scale, we use periodization to focus on different goals at different times because we adapt most efficiently this way. Day-to-day, the same principles are at work. Alternating one intensity with another is the way to get faster.
To answer the question at the beginning of this post: Yes, if what you’re running is truly junk, then it might be time for change. If you’re blurring the physiological lines between workouts, so that one is indistinguishable from the next in terms of intensity and duration, then it might be time to take out the trash. But keep those workouts distinct; give it everything you have on speed days and force yourself to go (extra) slow on the easy days, and you’ll avoid the junkyard.