What is 80/20 training and why should you be trying it? (2024)

Here’s an idea: do most of your training at a leisurely pace and, come race day, you’ll be nailing your goals like Kipchoge on an autumn Berlin morning. It may seem far-fetched, but it’s supported by the latest research, which tells us that running slower for the bulk of our runs really can reap huge rewards.

‘From our research, it’s clear that elite athletes (including Kipchoge) train around 80% of the time at what we’d call low intensity, and they spend just 20 per cent of their time training hard,’ says Dr Stephen Seiler of the University of Agder, Norway, one of the world’s foremost exercise physiologists.

Seiler’s endurance epiphany occurred in the early 2000s when he analysed a huge swathe of studies into training intensity and duration. Since then, further studies by the likes of sports scientists Veronique Billat, Augusto Zapico and Jonathan Esteve-Lanao have corroborated Seiler’s theory that 80/20 is the holy grail of running fitness.

What is 80/20 training?

‘Whether the elite is training 20 or 40 hours a week, the training broadly follows this 80/20 split,’ says Seiler. At the extreme end, Paula Radcliffe adhered to an 80/20 split at her peak in 2003, when 12 of her 15 runs (160 miles per week in total) over an eight-day cycle would be at a low intensity. But does the principle hold true for those of us who are lucky to squeeze in three or four runs a week?

‘That’s the real win,’ says Seiler. ‘We undertook further research and showed that it’s equally relevant if you’re training four sessions a week or 14.’ And, he adds, it’s arguably more important for recreational runners because we often get our intensity all wrong when it comes to long-term fitness progress.

‘Many recreational runners feel like they must go hard every time, so they do a lot of training in this threshold area,’ says Seiler. ‘They’ll improve initially, but then they stagnate. The problem is, they become too fatigued to do high-intensity sessions.’

Studies show that recreational runners naturally gravitate towards running 50 per cent at moderate to high intensity and 50 per cent at low intensity. And when Esteve-Lanao asked experienced club runners to follow either this 50/50 split or an 80/20 split, the 80/20 group improved their 10K times by five per cent compared with 3.5 per cent for the 50/50 group.

The runners in this study ran just over 30 miles per week, but what happens if you run less than that? Does the 80/20 rule still apply below this threshold?

A study conducted by Luca Festa at the University of Verona compared recreational runners logging roughly half an hour a day of running for eight weeks. One group followed a polarised training program, where 77% of training was done at low intensity, 3% at moderate intensity and 20% at high intensity, while the other group performed 40% of their training at a low intensity, 50% at moderate intensity and 10% high intensity.

The volume was adjusted to ensure that the total training load was equal for the two groups, so the 77/3/20 group ran slightly more (32 minutes) than the 40/50/10 runners (27 minutes). They found that both methods obtained similar results when it came to improvements in fitness – but the 40/50/10 group saved 17% less time – showing that the 80/20 approach is as effective as training at a high intensity in low-mileage runners, it just takes more time.

What are the two intensity levels?

For simplicity, there are two intensity levels to 80/20: low on one side, medium to high on the other. Seiler’s research isolates the cut-off between the two as the ventilatory threshold, which falls between 77 and 79 per cent of maximum heart rate in well-trained runners, and is similar to the lactate threshold.

Various tests can be done and measurements taken to identify what your boundaries are but an easy way to determine your intensity levels is by manually calculating your heart-rate training zones – or, even easier, allowing your running watch to do it for you. The main thing to remember is that low-intensity easy runs should be done at a pace that you are able to hold a full conversation at.

Why should I run easy?

So what are the physiological benefits of running easy? Easy runs train the cardio and respiratory systems to work more efficiently, allowing you to run with less effort during higher-intensity runs.

Slow runs also train your slow twitch muscle fibres – which allow us to work aerobically – driving adaptations that make us better at endurance running. And so if we don’t include enough of these in our plan, we not getting enough of the appropriate aerobic stress needed for long-distance running.

Slower running also helps to strengthen the tendons, ligaments, joints and bones without causing excessive stress to them.

Both moderate- and high-intensity work cause the body too much stress to be performed in large amounts, which compromises recovery.

This doesn’t just increase your injury risk but means you go into your next high-intensity session unable to perform at your best due to fatigue, so those sessions aren’t as effective.

That’s why Kipchoge, for example, spends a lot of his time training at a low intensity – it allows him really give his hard sessions a proper go. And he only does it twice a week, in the form of one track session and the other an unstructured fartlek session. The rest of his miles are done at a very easy pace.

Where did the concept of training slow to race fast first come from?

Seiler’s breakthrough was pinpointing the precise ratio of the 80/20 split, but the concept of training slow to race fast isn’t new. Legendary New Zealand coach Arthur Lydiard employed the idea to great success with the athletes he worked with back in the 1950s. And according to research scientist Inigo Mujika, it’s a template that actually goes back an awful lot further. In his paper ‘Do Olympic Athletes Train as in the Paleolithic Era?’, published in Sports Medicine, the Basque physiologist proposed the idea that humans respond better to training stimuli that mimic the physical patterns of our ancestors.

‘Faster running was important for scavenging, pursuing prey and escaping predators,’ says Mujika. ‘This was married to low-intensity tasks that were performed on a regular basis. These daily activities could have included normal social interactions; maintenance of shelter and clothing; and gathering of wild plants, grains and fruit.’

Our ancestors, Mujika continues, probably actively planned their daily physical activity, too. ‘It may be expected that our predecessors naturally decided to rest or perform light activities after hard days to be better prepared for the next hard day(s)…This fits perfectly well with the 80/20 hypothesis.’

Room for manoeuvre

Returning to the present day, Seiler says the 80/20 split should be used as a guideline rather than a strict rule, so he ‘can live with training 85/15 or 75/25’. But he stresses that you shouldn’t veer too far away. And don’t overcomplicate things: ‘The 80/20 rule is based on categories,’ he says. ‘I class a session as either hard or easy. If I do an interval session, even though the effort and heart rate will fluctuate, it’s hard. If you run four times a week, no matter the length, if one run is hard then that’s a 75/25 split.’

Another thing to bear in mind is that ‘hard’ doesn’t have to floor you. ‘Often, when people do intervals, they think they have to get to a point where they throw up,’ says Seiler.
‘We don’t see that with the elite athletes. They spend a lot of minutes at a slightly lower intensity – 90 per cent instead of 95 per cent.’

Low-intensity sessions should precede and follow hard efforts, and that’s especially true for runners aged 50 and over, who require longer recovery periods between intense sessions. If you’re keen to reap the rewards of 80/20, start with a detox week of ‘slow’ where you run every session at low intensity, then use this proven physiological formula to determine how many easy/hard runs you're doing each week.