Easy running, and why most of yours should be easy
The highest-leverage change most runners can make is to slow down the runs that were never supposed to be hard.
- Easy means conversational — a full sentence, out loud, without planning your breathing round it.
- Four-fifths of your weekly time is the usual rule of thumb — useful as a check, not a target to hit.
- Easy running is not junk mileage. It is where most aerobic adaptation happens.
- If your easy runs are too hard, your hard sessions will be too easy. The two failures arrive together.
Most of the time you spend running should be easy enough to hold a conversation through. For a lot of runners, moving toward that is the highest-leverage change available — larger in its effect than adding a session, buying anything, or trying harder.
You will see this expressed as eighty–twenty. It is a useful figure and it is not a law: it comes from observing how experienced endurance athletes distribute their training, and it says nothing about what the remaining fifth should contain, or whether it applies to someone running three hours a week.
What easy is for
What is not a rule of thumb is the mechanism. Easy running develops the aerobic system that everything else sits on: more capillaries, more mitochondria, a heart that moves more blood per beat, muscles better at using fat for fuel. Those adaptations respond to time spent at a manageable effort, not to intensity.
Crucially, it costs very little to recover from. That is what makes it repeatable — and repeated stimulus is what produces change.
How to find the effort
- Say a full sentence out loud. If it comes in fragments, slow down.
- Nose-breathing should be roughly possible, even if you do not do it the whole way.
- You could go further. Not much further — but the thought is not absurd.
- You finish thinking you could have done a bit more. That is a well-judged easy run.
Effort, not pace, is the instruction. The same easy effort will be a very different pace in August than in March, and slower again into a headwind or up a hill — and it should be.
Why running them slightly too hard is so costly
This is worth being precise about, because the cost is not obvious.
A moderately hard easy run produces slightly more aerobic stimulus than an easy one, and costs considerably more recovery. Do that four times a week and you arrive at your genuine quality session already tired. The session then goes badly — not disastrously, just flatly — and you get less from the part of the week that was supposed to make you faster.
So the two failures arrive together: the easy runs are too hard and the hard runs are too easy. The whole week collapses toward the middle, which is the one place that reliably builds nothing.
The uncomfortable part
Easy running often feels too slow to be worth doing, especially if you are used to finishing runs tired. Sometimes it means being overtaken. Frequently it means a pace you would not volunteer publicly.
It is still the method. Runners who race well spend most of their week running slower than people assume — and our view is that the ones who stall for years are often the ones who never let a run be genuinely easy.
Common questions
How slow should an easy run be?
Slow enough to speak a full sentence out loud. Considerably slower than 5K race pace — but the conversational test is more reliable than any number because it adjusts for heat, hills and how tired you are.
Is easy running just junk mileage?
No — that phrase usually describes moderate running, not easy running. Genuinely easy running builds aerobic capacity at a low recovery cost, which is what allows the frequency that drives improvement.
Why do I feel worse on easy runs than hard ones?
Often because they are not easy. A run at an awkward middle effort feels worse than either a genuinely easy run or an honest hard session, and does less than either.