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

80 20 running
What is 80/20 training? Getty Images

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 your runs really can reap huge rewards.

"From our research, it’s clear that elite athletes train around 80 per cent 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 nearly a decade ago 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.

Across the threshold

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.

While research has established the benefits of 80/20, it’s still unpicking the precise physiological rationale behind the split. However, broadly speaking, Seiler suggests you enjoy greater benefits from high-intensity running when you are training predominantly at a low intensity. Also, both moderate- and high- intensity work cause the body
too much stress to be performed in large amounts.

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 the information on the following pages as your complete guide to unlocking the benefits of this proven physiological formula for success.

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