Should I follow the 80:20 rule in sub-3 training?
The biggest sub-3 gains often come not from pushing harder – but from knowing when to hold back.
To run fast, you often need to slow down
When I first started running properly, I only really had one gear. Sure, I’d pick it up to overtake someone or push the final kilometre – but, for the most part, I just ran. I didn’t think in terms of zones or paces. I just put my shoes on and went out the door.
It was only when I started working with a coach that I began to understand the idea of training in distinct zones – five perceived effort levels, from very easy to flat-out. It took a while to click but, once it did, I could immediately sense which zone I was in. I didn’t need heart rate data or power readings – just experience. That learned intuition changed everything.
Like many runners, I used to assume faster was always better. When I first joined Strava, I’d try to make every run a personal showcase – slightly faster, slightly further, a little more effort. It was completely unsustainable. My body never had a chance to absorb the training because I never really backed off. And that meant I never fully improved.
That’s where the 80:20 principle comes in.
What is 80:20?
The 80:20 rule – popularised by coach and author Matt Fitzgerald in 80/20 Running – is simple: 80% of your training should be at low intensity, and just 20% should be at moderate to high intensity. That doesn’t mean jogging around all week and sprinting on Sundays. It means strategically planning your week so that your hard sessions are hard – and your easy runs are genuinely easy.
For a sub-3 runner, that might mean:
- Two or three key quality sessions per week (e.g. intervals, tempo, long run with speed)
- Everything else at low intensity – which for many is significantly slower than marathon pace, often 60–90 seconds per km slower
Why it works
Physiologically, this balance helps you develop both your aerobic base and your race-day speed. Easy running builds endurance by strengthening your heart, improving oxygen delivery and recruiting slow-twitch muscle fibres – the ones you’ll rely on most during the marathon.
Hard sessions target lactate threshold, VO2 max and neuromuscular efficiency – essential for speed and sustained pace under fatigue. But they’re also demanding. Do too many, and you break down. Do them when fatigued, and they lose their effect.
By sticking to the 80:20 balance, you avoid the ‘grey zone’ – that middling effort level where you’re working too hard to recover but not hard enough to get faster.
How to make it work
Planning your week around 80:20 doesn’t have to be complicated. A typical sub-3 training week might look like this:
- Monday: Easy recovery run (Zone 1–2)
- Tuesday: Quality session (e.g. intervals or hills – Zone 4–5)
- Wednesday: Easy run
- Thursday: Medium-long run, steady (low Zone 3 at most)
- Friday: Rest or very easy jog
- Saturday: Tempo session or parkrun effort (Zone 3–4)
- Sunday: Long run (often starts easy, may include segments at marathon pace)
Even on harder weeks, the bulk of the weekly volume remains easy. That’s the key: intensity is measured by time or distance – not number of sessions.
You’ll also need to master restraint. Don’t get drawn into pacing battles on Strava or “feeling good” and pushing an easy run harder than planned. If you finish a run thinking, “I could’ve done more,” good. That means you’ve left something in the tank.
A small but telling detail here: many sub-3 runners label their easy runs on Strava as “ER” (Easy Run) or note them as “Z1” rather than calling them “Easy” outright – because 5:00/km pace can look like showing off to outsiders. It’s not. For them, that’s genuinely easy – and they know the value of keeping it that way.
The paradox: slowing down to speed up
The irony is this: many runners who want to run faster try to prove it on every run. But speed doesn’t come from forcing it – it comes from structuring it. The best way to run a faster marathon isn’t to run every run fast – it’s to train smart, with purpose, patience and consistency.
For many sub-3 runners, the breakthrough doesn’t come from the interval session – it comes from finally learning to go easy when easy is needed.
Sometimes, the best way to run 4:15 per km in a marathon… is to spend most of your week running 5:30s.
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