Want To Get Faster? Here’s Why More Slow Runs, and Less Speed Work, Is The Answer


When I coached high school track and cross country, there was an assistant coach who would tell the runners, especially during the long, slow, base-building summer runs, you’ve got to go slow to go fast.

They would look at him sceptically, but his advice, while perhaps counterintuitive, is actually quite sound.

Research, in fact, has shown that while we may instinctively feel a need to push the pace most of the time to get faster, doing most runs at a slow pace is more likely to yield the desired results.

According to runner and fitness expert, Matt Fitzgerald in his book 80/20 Running, running too hard too often is “the single most common and detrimental mistake” made by runners, as the “secret” to becoming a faster runner is “going slow most of the time.”

If you suspect you’re running too many of your miles too fast and are curious about the potential benefits of going slow more often…

Keep reading!

In this article, we will talk about:

  • The history and science behind slower running
  • What do we mean when we talk about “hard” running and “slow” running
  • How you can incorporate this knowledge into your training

Let’s jump in!

Want To Get Faster Heres Why More Slow Runs And Less Speed Work Is The Answer

The History and Science Behind Slower Running

Arthur Lydiard

In the 1960s, New Zealander Arthur Lydiard devised a training method for runners that emphasized slower running with a relatively small amount of speed work.

His method was adopted by runners, who had success with the method, and elite runners continue to follow his ideas and run a majority of their miles at an easy, conversational pace.

Recreational runners, however, have been less inclined to follow this method, and tend to run at least half of their miles at a moderate or hard effort level.

Runners’ resistance to slower running appears to be based on scepticism that slower running can be beneficial, but research has confirmed its benefits.

Lydiard advises newer runners to take the word “hard” out of their vocabulary, explaining that easy running will result in gradual and important physiological changes, including strengthening of your muscles, joints, and ligaments.

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Stephen Seiler

Stephen Seiler, an exercise physiologist and professor in Sports Science at the University of Agder in Norway, has done extensive research on endurance training and intensity distribution and confirmed Lydiard’s theories.

Seiler analyzed high-level athletes in a variety of different sports, including runners, and discovered most world-class athletes do approximately 80 per cent of their training at low intensity and 20 per cent at high intensity (now often referred to as the 80/20 Rule, or 80/20 training).

Seiler then designed studies where athletes were divided into two groups — one that followed an 80/20 plan and one that did more hard training — and consistently found the athletes who followed an 80/20 training plan experienced significantly more improvement than athletes who did more than 50 per cent of their training at high intensity, or even those who followed a 65/35 plan.

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Why Does The 80/20 Plan Work?

While testing has consistently confirmed that an 80/20 plan yields the best results, scientists are not entirely sure why this is so.

As indicated by Fitzgerald, theories include that low-intensity training is more beneficial than previously thought, particularly in regard to building endurance/fatigue resistance, and that high-intensity training, while necessary to increase VO2 max, improve running economy, and strengthen the aerobic system, is stressful on the body and likely to impede progress if done in large amounts.

In any regard, as the evidence shows an 80/20 plan is the optimal ratio for those runners hoping for faster times and improved overall performance, it is certainly worth considering.

Fitzgerald, in fact, notes that Seiler’s research is so compelling it should serve to “remove the guesswork from the training process” even for non-elite runners and make running “a simple matter of planning your workouts in accordance with the rule and monitoring your running intensity during each work out to ensure you’re where you’re supposed to be.”

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What Do We Mean by “Hard” Running and “Slow” Running?

Of course, while following the 80/20 Rule may seem simple, it requires an understanding of what “hard,” or high intensity, running is and what “slow,” or low intensity, running is.

According to Fitzgerald, low-intensity running is running below ventilatory threshold, which is the point when “your breathing becomes laboured” and you feel as if you cannot “draw in as much air your body wants.”

There are several ways to measure running intensity and find your ventilatory threshold, but Fitzgerald notes the most practical methods involve relying on:

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Perceived Effort

Perceived effort, or rate of perceived exertion (RPE), is simply your subjective assessment of how hard you feel you’re working.

This assessment can be quantified by using a scale of 1 to 10, with 1 being minimum effort, such as a gentle stroll you feel you could maintain forever, and 10 being, essentially, a full sprint you could not sustain for more than about 30 seconds.

In this context, low intensity is considered to fall within the 1 to 4 levels, moderate intensity is levels 5 and 6, and high intensity is levels 7 through 10.


Heart Rate

Heart rate involves more variables, but, for simplified purposes, it’s important to determine your heart rate at your lactate threshold, which marks the upper end of the moderate-intensity range and corresponds to an RPE of 6.

To determine your lactate threshold heart rate, Fitzgerald suggests running a 30 minute time trial while wearing a heart rate monitor and averaging your heart rate over the final ten minutes. Alternatively, he suggests simply noting your heart rate while running at an RPE of 6 or at a point where talking is slightly uncomfortable.


Pace is a measure of how fast you run a specific distance. To determine your intensity in terms of pace, Fitzgerald suggests you note your pace when running at different RPEs (or heart rates, if you have that information).

Another option is to input a recent race time into an online pace calculator, such as the one created by Greg McMillan, with his Recovery Run Pace and Easy/Long Run Pace indicative of low intensity running, Tempo Run Pace corresponding with moderate intensity running, and Speed Pace or Sprint Pace representing high intensity running.

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Once you have a reasonable idea of what constitutes low intensity, moderate intensity, and high intensity, you can begin to incorporate the 80/20 Rule, or at least some version of the “mostly easy” training theory, into your own running plan.

How Can I Incorporate This Science Into My Training?

Fitzgerald emphasizes that the 80/20 ratio is an approximation and that runners should not worry about being a little off one way or the other. Rather, he suggests designing a training plan that divides easy runs and hard runs (which include runs done at both moderate and hard intensity) within close range of an 80/20 ratio.

Of course, even hard workouts involve some segments of easy running, either as part of the warm-up or cool down or during the recovery segments during interval sessions, so a more accurate way to achieve an 80/20 balance is to determine your total weekly mileage and run no more than 20 per cent of that mileage at a moderate or hard intensity.

You can base your 80/20 calculations on either time spent running, or miles run, it’s up to you!

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Adapting your current running schedule

If you’re like most runners, you’re probably looking at these numbers and realizing that you definitely run more than 20 per cent of your miles at a moderate or high intensity.

According to Fitzgerald, research shows that recreationally competitive runners typically run more than half their miles at a moderate or high intensity, so you’re not alone if your current running is far from this ideal.

Given the extensive research which shows that limiting your harder running to no more than 20 per cent of your total miles is the ratio most likely to lead to improvement, however, it makes sense to try it and see what it can do for you.

It’s also important to keep in mind that the hard 20 per cent of runs can be done in a variety of ways, including longer sustained tempo runs, hill running, or repeats of short, fast intervals.

The key to this type of running does not lie in any specific running plan, merely the overall percentage of intensities, so there is room to create a plan that makes sense for you.

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As with any plan, of course, there are some caveats:

4 times When the 80/20 plan doesn’t work

1. Individual Differences

Some people respond better to a slightly different ratio of hard and easy running, so pay attention to how you progress with this training and feel confident that some minor tweaking of this ratio is fine if it seems to suit you.

2. Training Cycle Adjustments

During certain periods of a training cycle, it may be optimal to alter the ratio somewhat.

During an initial, or base phase, when you are simply trying to develop or maintain a running habit and increase mileage, low-intensity running can make up more than 80 per cent of your total running.

Conversely, during a taper phase (a one or two week period of decreased running prior to a significant race), while the overall mileage will decrease, the percentage of harder running may increase somewhat.

Fitzgerald notes that research shows the best way to “rest and prime the body for racing” is to “sharply reduce the overall training volume while continuing to do high-intensity workouts.”

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3. When Training For Shorter/Faster Races

While moderate-intensity and high-intensity running are lumped together for purposes of 80/20 running, evidence suggests that when training for longer endurance events, runners may see more improvement with a focus on moderate-intensity running.

Whereas those aiming for shorter, faster races may benefit from emphasizing high intensity running in their 20 per cent.

4. After A Break In Training

If you have been ill or injured, or otherwise sidelined for a while, you may want to minimize the harder running for a while.

Should You Try The “Mostly Slow” Approach?

If you think you’re doing more than 20 per cent of your miles at a moderate or high intensity, are not progressing as much as you would like, and are curious about the idea of running slower to get faster, then get out there and run …. just keep it mostly slow!

For some slow running inspiration, check out the following articles:

On Long Runs:

On Recovery Runs:

Photo of author
A lifelong runner and USATF Level 1 coach of high school cross country and track, Sarah enjoys racing all distances, from the mile to ultras. She is a recent transplant from California to Seattle and spends her free time exploring her new neighborhoods by foot.

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