PR Pacer · Training Notes
What Are "Junk Miles," Actually?
Not just miles you didn't need.
"Junk miles" gets used loosely, usually as a way to dismiss easy or slow running as pointless. That's not actually what the term means, and treating it that way leads runners to cut the wrong things. Junk miles are effort with no clear purpose in your training — not miles that happen to be slow.
The classic version
The clearest example: running hard on a day meant to be easy, with no real benefit to show for it, just fatigue you end up paying for on the day that was actually supposed to be hard. That's a genuine junk mile — not because the pace was wrong in isolation, but because it worked against the purpose the day was supposed to serve.
Slow doesn't mean junk
This is the part that trips people up: miles aren't junk because they're slow. An easy run done at the right easy effort is doing exactly its job — building aerobic base, aiding recovery, adding volume your body can actually absorb. Calling that a junk mile misunderstands what it's for. Miles become junk when they cancel out tomorrow's real workout, not when they're simply unhurried.
The question that actually matters
The fix isn't running less overall. It's making every run answer a question: what is this one actually for? An easy run — recovery and aerobic base. A tempo run — threshold fitness. A long run — endurance. A run with a clear, honest answer to that question is doing real work, whatever its pace. A run with no answer — run hard out of habit, or run at some undefined in-between effort that's neither restorative nor a real stimulus — is the one actually worth reconsidering.
Purpose beats pace. That's the actual test, not how fast or slow any single run happens to be.
Ask your coach what a specific session is actually for.
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Frequently asked
- What are junk miles?
- Not simply miles you didn't need — effort with no clear purpose. The classic version is running hard on a day meant to be easy, with no benefit, just fatigue you pay for later.
- Are slow miles junk miles?
- No. Miles aren't junk because they're slow — they're junk when they cancel out tomorrow's real workout. A properly-paced easy run is doing exactly its job.
- How do I avoid junk miles?
- Make every run answer a question: what is this one actually for? A run with no clear answer is the one worth reconsidering.