The Problem with “Junk Miles” — and Why Easy Doesn’t Always Mean Effective

Darius Silaghi

In endurance training, “easy miles” are often treated as inherently beneficial. They’re seen as safe, low-risk, and universally productive — the kind of work that quietly builds fitness in the background.

But not all easy running is created equal.

And for certain athletes — especially middle-distance and track-focused runners — there is a point where “easy” becomes too easy to be useful, while still carrying a cost.

That’s where the concept of junk miles starts to matter.

When Easy Stops Being Productive

Easy running has a clear purpose.

It supports aerobic development, promotes circulation, reinforces movement patterns, and allows athletes to accumulate volume without excessive fatigue. Done correctly, it’s one of the most important tools in endurance training.

But the key phrase is done correctly.

If the pace drops too far below an athlete’s aerobic threshold — particularly in well-trained runners — the physiological stimulus becomes minimal. Oxygen consumption is low, cardiovascular stress is limited, and the session contributes little to meaningful adaptation.

At the same time, the mechanical cost of running doesn’t disappear.

Every stride still produces impact. Every kilometer still loads tendons, joints, and connective tissue. The body still has to absorb that stress, regardless of how slow the pace is. So you end up in a situation where stimulus is low, but cost is still present

That imbalance is what turns easy running into junk volume.

Why This Matters More for Track Athletes

For long-distance runners, very low-intensity running can still play a role. Their training is heavily aerobic, and even small amounts of stimulus accumulate over time.

But for track athletes — 800m, 1500m, even 5k specialists — the equation is slightly different.

Their performance depends on:

  • high-quality aerobic power

  • speed and neuromuscular efficiency

  • precise intensity distribution

If a session is too slow, it doesn’t meaningfully support any of these qualities. It doesn’t develop aerobic power, it doesn’t reinforce race-relevant mechanics, and it definitely doesn’t contribute to speed.

It just adds time on feet. And over weeks and months, that matters.

Because training isn’t just about what you do — it’s about what you choose to spend your recovery capacity on.

Stress Without Direction

The real issue with junk miles isn’t that they’re easy.

It’s that they’re directionless.

Every session should have a role:

  • building

  • maintaining

  • recovering

  • preparing

When pace drops below a useful range, the session stops serving a clear function. It’s no longer recovery — because it still creates mechanical stress. It’s no longer development — because the stimulus is too low.

It exists in a grey zone. And grey zones are expensive in high-level training. Because they take from the same pool of recovery resources that your quality sessions depend on.

A Better Alternative: Preserving the Intent, Reducing the Cost

If the goal of a session is low-intensity aerobic work, then the question becomes:

Do you need to run to achieve it?

In many cases, the answer is no.

This is where low-impact modalities can play a valuable role — not as replacements for running, but as tools to execute the intent of a session more efficiently.

An easy aerobic session performed on a bike, for example, can:

  • reach the same cardiovascular zone

  • maintain oxygen uptake

  • support recovery

…while significantly reducing mechanical stress.

Tools like the Concept2 BikeErg are particularly well-suited for this type of work. They allow for precise control of intensity, smooth power output, and repeatable aerobic sessions without the cumulative impact of running.

For athletes in high-volume phases, or those balancing frequent quality sessions, this can make a meaningful difference.

Final Thought

There’s a tendency to think that more time on your feet automatically leads to more progress.

But at a certain level, that stops being true: some even dare to say that going 30-40% slower than threshold pace is barely worth it, run slower that that and you are already in a grey zone, not gaining additional recovery-benefits but extending time on feet!

Back to blog
Sponsors