80/20 Running: Run Stronger and Race Faster by Training Slower

by Matt Fitzgerald

moderate intensity (which Esteve-Lanao and Seiler refer to as zone 2) and too little at low intensity (zone 1).

As it turned out, the runners who did about half of their training at low intensity lowered their 10K time from an average of 39:24 to 38:00. That’s an improvement of 1:24, or 3.5 percent. Those who did roughly 73 percent of their training at low intensity lowered their 10K time from an average of 39:18 to 37:19. That’s an improvement of 1:59, or 5.0 percent.

Overall, the results of this study strengthened Esteve-Lanao and Seiler’s hunch that 80/20 training was more effective for all runners, including low-mileage recreationally competitive runners.

What do the findings of the Salzburg study teach us? Two things: First, they teach us that high-intensity training is essential, but that a little goes a long way. The two groups that completely avoided the high-intensity zone experienced the least improvement. But the group that did the most high-intensity work improved less than the polarized group, which did 2.5 times more training at low intensity than at high intensity.

The physiological cornerstone of running performance is aerobic capacity, or the body’s ability to extract oxygen from the environment and use it to release energy from muscle fuels. The human aerobic system includes the heart and lungs, the arteries and capillaries that deliver blood to the muscles, the blood itself, and mitochondria, which are little “factories” within muscle cells where oxygen is used to release energy from metabolic fuels. Running induces changes in all of these organs that serve to increase aerobic capacity.

The key requirement for strengthening the aerobic system is stress. Unless you subject your aerobic system to a significantly greater challenge than it faces when you are at rest, it will not adapt. Specifically, you need to elevate your heart rate to at least 60 percent of maximum. So, if your maximum heart rate is 185 beats per minute (BPM), you must run fast enough to get your heart rate up to roughly 111 BPM to boost your aerobic fitness.

While 60 percent of maximum heart rate is the minimum threshold for aerobic benefit, increasing the intensity beyond that threshold brings additional benefits. Research has repeatedly demonstrated that high-intensity exercise strength...

However, there are some things that low-intensity exercise does better. For example, a number of studies have shown that during prolonged running at low intensity, the muscles release large amounts of a cell signaling compound called interleukin-6 (IL-6), which contributes to fatigue. Well-trained runners produce less IL-6, and this is one reason they are more fatigue resistant. It is believed that exposure to large amounts of IL-6 during running is itself the primary trigger of physiological adaptations that reduce IL-6 release in future workouts and boost endurance. In turn, the primary trigger for IL-6 release is depletion of glycogen fuel in the working muscles. Long, slow runs cause much higher levels of glycogen depletion—and hence also of IL-6 release—than do short, fast runs.

So the effects of low-intensity and high-intensity exercise on the aerobic system are somewhat complementary. Maximizing aerobic capacity therefore requires that a runner do some of both. The question, then, is not whether one is “better” than the other and thus ought to be done exclusively. The question, rather, is how high-intensity and low-intensity training should be balanced.

the stressfulness of running is not strictly determined by intensity. Rather, it is determined by the volume of intensity.

Research shows that low-intensity training is truly a gift that keeps on giving. The more slow running you do—up to a point, of course—the more you get in return.

As I mentioned above, the farther a person runs, the more fitness-boosting IL-6 his muscles release, while the fitter a person becomes, the less IL-6 the muscles release in a run of any given distance. A beginner may produce enough IL-6 in a slow thirty-minute run to stimulate positive adaptations, whereas an experienced runner may not. To stimulate further adaptations, this second runner will need to run farther, but she need not run faster—in fact, running faster won’t help in this instance because, as we saw above, IL-6 release is affected by the duration of running more than the speed.

Runners release more IL-6 when they start out with semidepleted glycogen stores, and runners who train frequently are often unable to ful...

High-intensity running is different. While a small amount of high-intensity running is more beneficial to the aerobic system than is a small amount of low-intensity running, larger amounts of faster running offer no additional benefit. In fact, large amounts of high-intensity training are so stressful to the body that they suppress the parasympathetic nervous system, resulting in chronic fatigue and loss of performance. So the sum of what we know about the physiological effects of low-i...

So runners must be at least as wary of sabotaging their training with excessive moderate-intensity running as they are of overcooking themselves with too much speed work.

Before we get to that, let me first explain what a higher aerobic capacity will not do for you, and that is make you faster in any pure sense. In fact, maximizing your aerobic capacity through optimal training will actually make you a slower sprinter over short distances.

What’s more, training for increased aerobic capacity also reduces anaerobic capacity, or the ability of the muscles to burn fuel quickly without oxygen in support of intense efforts one notch below a full sprint.

In his famous Sports Illustrated article from 1962, Arthur Lydiard argued that distance runners do not need to increase their maximum speed. He was right about that. But it turns out that runners can’t increase their maximum speed if they train for increased aerobic capacity. Sacrificing VO2max for raw speed would be a giant mistake for any distance runner, because boosting aerobic capacity through optimal training offers two benefits that matter much more to this type of athlete: 1) it increases the speed that runners can sustain over longer distances; and 2) it increases how far runners can go at submaximal speeds. It is no accident that in the Salzburg study, the training program that induced the largest increase in aerobic capacity (polarized) also yielded the greatest improvements in time to exhaustion and in the highest speed attained in an incremental exercise test.

Aerobic metabolism is more efficient and less fatiguing than other ways the muscles have of powering themselves. The more oxygen your muscles are able to use to fuel your running, therefore, the faster you can run over long distances and the farther you can run at race speeds. Interestingly, increases in aerobic capacity are associated with much larger gains in fatigue resistance (the sustainability of speed) than in speed over distance.

The giant disparity in the scale of the two main benefits of increased aerobic capacity gives us reason to suspect that improved fatigue resistance in runners is not entirely accounted for by gains in VO2max. This suspicion is supported by studies in which runners lose fitness instead of getting fitter. For example, in a study conducted by Danish researchers in 1985, well-trained endurance athletes were asked to reduce their training volume from between six and ten hours per week down to just thirty-five minutes per week for four weeks. At the end of that four-week period, their VO2max was unchanged but their time to exhaustion at 75 percent of VO2max had dropped by 21 percent. The athletes had lost a ton of fitness, specifically fatigue resistance, but you wouldn’t have guessed it from looking at their aerobic capacity.

At the elite level, runners who take up the sport in high school typically attain their lifetime peak VO2max by their second year of college. Their best race times, however, often don’t come until a full decade later.

What had changed was Radcliffe’s ability to sustain the speed she’d always had over longer distances. By 2003, she was running as much as 160 miles per week on an eight-day cycle that included fifteen runs, twelve of which (or 80 percent) were done at low intensity. Her VO2max was still unchanged, but in that year, she set a still-standing marathon world record of 2:15:25 and ran a half marathon at an average pace of 5:00 per mile, or 2 seconds per mile faster than the pace she had run for 3000 meters (less than two miles) when her VO2max was at its peak.

Low-intensity, high-volume training develops the sort of suffering tolerance that enhances fatigue resistance more effectively than does speed-based training. Fast runs may hurt more, but long runs hurt longer. The slow-burn type of suffering that runners experience in longer, less intense workouts is more specific to racing. Speed-based training teaches the mind to expect a quick end to the discomfort of running in a fatigued state.

Runners often observe that very long runs and races are more mentally challenging than shorter ones. There’s a reason for this. Studies have shown that prolonged exercise at low intensity fatigues the brain to a much greater degree than does high-intensity exercise that doesn’t last as long.

We already know that inducing fatigue in the body through exercise triggers adaptations that make the body more resistant to fatigue in the future. Brain fatigue works the same way. Low-intensity runs lasting long enough to tire out the brain strengthen the parts of the brain that aid fatigue resistance. Shorter, faster runs aren’t as effective at fatiguing and strengthening these brain areas, which include the insular and temporal lobes, whose job is to perceive the physical elements of emotional states (such as the discomfort of extreme effort), and the anterior cingulate cortex (ACC), whose job is to resolve internal conflicts (such as the conflict between the desire to keep going and the desire to quit when one is running in a fatigued state). The stronger these areas become, the more slowly a runner’s sense of effort will increase in races and workouts and the longer he or she will be able to endure the agony of severe fatigue.

It is important to understand that the duration of exercise matters far more than does the intensity of exercise with respect to the goal of enhancing fatigue resistance in the brain. What counts is not how hard the muscles are working but rather how long the brain is required to stay focused on the task at hand. In fact, research has shown that the brain can be fatigued at rest in a way that increases fatigue resistance and physical endurance.

the anterior cingulate cortex—the part of the brain that helps runners resist the temptation to quit.

These results demonstrate that brain fitness makes a major contribution to physical endurance that is completely independent of physiology below the neck. You don’t even have to exercise to increase brain fitness and fatigue resistance in endurance exercise. All it requires is sustained mental focus on a cognitively demanding task. Of course, building brain fitness through running itself will improve running performance more effectively than building it outside of running. But since the development of brain fitness requires only prolonged task focus and does not require major strain on the body, long runs at low intensity represent the most effective way to boost the brain’s capacity to resist fatigue. This helps explain why runners such as Paula Radcliffe improve so much by running a lot, mostly at low intensity, and why no runner improves as much with speed-based training.

Imagine for a moment that some clever chemist has developed a serum with the power to equalize running fitness among all who ingest it. Just swallow two drops and instantly you have exactly the same amount of running fitness as everyone who has done the same. Now, let’s say that you and ninety-nine other runners who have sampled the serum compete in a 10K race. What will happen? Will all of you tie for first place? Not a chance. The reason is that fitness is not the only factor that determines running performance. A separate factor is running skill.

To be a skillful runner is to have an efficient stride. The standard measure of stride efficiency is running economy, which is roughly equivalent to automobile fuel economy. Whereas fuel economy is represented as the amount of fuel required to travel a given distance, running economy is represented as the amount of oxygen required to sustain a given speed. All runners become more economical through training, which is to say that they exhibit a trend toward requiring less oxygen to sustain the same speeds.

Research has consistently shown that forced alterations to an individual’s natural running form almost always worsen performance instead of improving it.

So, if correct technique is not the “something special” about a runner’s movements that constitutes the essence of skillful running, then what is? Arthur Lydiard hinted at an alternative in his celebrated 1962 article in Sports Illustrated. That article contained exactly one paragraph on the topic of form. In four short sentences, Lydiard said everything he felt a runner needed to know about the matter. “Forget about form,” he wrote. “If a joker throws his arms around, that’s fine, so long as he is fit and relaxed. Then he runs smoother and easier, and form takes care of itself. We want the chap who can run for two or three hours and come back looking as fit as he did when he went out.”

This was Lydiard’s way of saying that there are lots of great runners who lack textbook form. But all great runners exhibit a subtler quality that we might call relaxed smooth ease. Unlike correct technique, this other quality actually matters to performance. The more rel...

Whereas good running form can be taught (to no avail), relaxed smooth ease is self-taught, or rather self-learned, emerging naturally through the normal fitness-building process. A low-intensity, high-volume (i.e., 80/20) approach to training is not only the most effective way to build running fitness, but is also the best ...

Only since Lydiard’s death in 2004 has science defined relaxed smooth ease and shown that simply running more, without trying to imitate some image of perfect running form, is truly the best way to become a more skillful runner. New studies have demonstrated that relaxed smooth ease is the visible manifestation of an acquired “quietness” in parts of the brain that control the body’s movements, a sort ...

The ultimate mark of skillful running is the ability to run with m...

There are many different schools of running technique instruction, but underneath their disparate labels they aren’t much different from one another. Whether they call it Chi Running, the POSE method, Evolution Running, Natural Running, or something else, the coaches who teach “correct” form all have pretty much the same thing in mind when they think about proper running technique: a high stride rate, a low stride length, minimal bouncing, and so forth.

Research stretching back more than forty years has consistently demonstrated that forced “corrections” to a runner’s natural form almost always worsen running economy instead of improving it.

Cavanagh concluded that runners either naturally adopt the movement patterns that are most efficient for them or they adapt to their chosen movement patterns so that these patterns become maximally efficient over time.

Unfortunately, it turned out the extra bouncing wasn’t wasteful at all. Changing their natural stride in this way made the runners less, not more, efficient.

The same thing happens when scientists meddle with runners’ natural foot strike. One study found that experienced runners who were natural forefoot strikers and those who were natural heel strikers had equal running economy, and that neither group became more economical when forced to switch. While a forefoot running style is commonly regarded as superior, the reality is that a heel striking style is more economical for those runners who come to this form naturally and unconsciously.

Many experts in biomechanics now believe that each runner’s stride automatically becomes more efficient over time so that conscious changes in technique are always unnecessary and usually counterproductive.

Science has shown that in adults, running economy improves drastically within weeks of the commencement of regular training.

In runners, a quiet brain yields a subtle play in the stride that observers may perceive as a sort of effortlessness.

Becoming a more skillful and efficient runner is more like growing a beard than it is like chopping wood. In other words, you don’t make it happen—you allow it to happen. The true essence of skillful running is not correct movements of the limbs but a quiet brain. Therefore the proper goal of all efforts to improve running skill is to reduce brain activity during the act of running. Any measure that helps a runner run more unconsciously is guaranteed to result in better performance. Likewise, any measure that increases brain activation during running will worsen performance.

Numerous studies have shown that people move less skillfully and learn motor tasks more slowly when they are required to focus their attention on their body. A few of these experiments have involved running. A 2009 study by German researchers, for example, found that runners were less economical when thinking about the movements of their body as they ran than they were when focusing on their breathing, and were less economical when focused on their breathing than they were when they paid attention to the environment around them.

If consciously changing your natural stride is not the best way to enhance your running skill, then what is? As we saw at the beginning of the chapter, Arthur Lydiard believed that high-volume training was the secret to developing relaxed smooth ease, which he correctly identified as the visible mark of skillful running.

Obviously, you can’t make much progress toward optimization with a single stride. It takes many thousands of strides to make measurable gains. That’s where repetition comes in. High-volume training packs more strides into less time, resulting in faster progress. And keeping the intensity low most of the time—in other words, following the 80/20 Rule—allows you to run more without burning out.

McGregor had proved that the more running a person does, the freer and more efficient his or her stride becomes, independent of changes in fitness.

Simply repeating the stride action, over and over, as much as possible, without interference, is the secret to becoming a more skillful runner.