Almost every runner wants to know how they can train to run faster. Improving speed tops most of our goal lists.
Of course, running ultimately comes down to numbers. To set a PR, you need a faster finishing time, which means sustaining a quicker pace throughout the race.
What sounds simple in theory is often difficult in practice. Many runners know the frustration of working hard in training only to see progress come slowly.
The common assumption is that the best way to run faster is simply to run faster more often—through workouts like track intervals, hill sprints, and tempo runs.
But many top coaches argue the opposite: you need to run slow in order to run fast.
This idea is the foundation of the 80/20 method, which suggests that roughly 80% of your training should be done at an easy effort, while the remaining 20% is reserved for harder workouts.
Often referred to as polarized training, this approach prioritizes easy running so that you can perform your faster sessions with greater quality and ultimately improve your performance.
What Is the 80/20 Method of Running?
The 80/20 method involves performing 80% of your weekly training volume at a slow, easy, conversation pace and the remaining 20% at a hard effort or high intensity.
In this way, the 80/20 rule in running is a form of polarized training.
Your easy days need to be easy, and your hard days need to be hard. The murky middle ground of “somewhat hard”1Seiler, K. S., & Kjerland, G. O. (2006). Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution?. Scandinavian Journal of Medicine and Science in Sports, 16(1), 49–56. https://doi.org/10.1111/j.1600-0838.2004.00418.x is not where you want to land.
A lot of runners get caught up in a ton of zone 2 running in their training plan instead of pushing hard enough in high-intensity workouts.
The primary purpose of the 80/20 method in running is to ensure that your body is fully recovering on your recovery days to maximize your faster running effort and performance on the hard days.
It also helps reduce the risk of overtraining and overuse injuries because your tissues have recovered.
The 80/20 approach was developed by Stephen Seiler, an exercise physiologist at the University of Agder in Norway, after decades of analyzing the training of elite athletes.
Seller noticed these elite endurance athletes all exhibited a similar distribution of their training loads, and a very polarized one at that—with about 80% of their training volume at a super easy effort and 20% very intense.
There was very little time spent in the middle.
Matt Fitzgerald later popularized the run slow to run fast 80/20 method of running, which has been adopted by competitive and recreational runners, covering distances from the 5K, 10K, half marathon, marathon, and beyond.
Why Run Slow to Run Fast?
If you are concerned that running such a significant percentage of your training at a slow pace will make you a slower runner, you are certainly not alone.
The concept that you should focus on slowing down to run fast is definitely counterintuitive.
However, there are several ways in which slower running can potentially help you to run faster, including:
#1: Improves the Efficiency Of the Aerobic System
Running slowly keeps your heart rate in the aerobic zone, which means you are taking in enough oxygen through your respiratory system to meet the oxygen demands of your working muscles.
Your muscles must generate ATP (cellular energy) while exercising to sustain physical activity.
This energy can be generated through several metabolic pathways, one of which is the Krebs cycle, or aerobic metabolism.
Both fat and glycogen (stored carbohydrates) can be broken down to create energy through aerobic metabolism.
The benefit of generating energy through aerobic pathways is that the metabolic byproducts do not “pollute” your muscles or cause fatigue. This is in contrast to anaerobic glycolysis, an energy-generating metabolic pathway that occurs when muscles don’t get enough oxygen.
If you’ve been running for some time, there’s a good chance you’ve heard of “lactic acid buildup” in your legs.
And, while this is a bit of a misnomer (it’s not actually lactic acid accumulating in your muscles but rather an increase in hydrogen ions), what people are referring to when they cite this buildup is the detrimental metabolic byproducts of anaerobic glycolysis that cause a burning, painful feeling in your legs and extreme fatigue.
Essentially, when the muscles produce energy in the aerobic training zone, you won’t have any acidic buildup in your muscles, so you can keep running comfortably and for much longer.
Running slowly improves the efficiency of your aerobic system due to adaptations such as increases in capillary and mitochondrial densities in your muscles, increases in the strength and chamber size of your heart muscle, and increases in blood plasma volume.
As a result of these adaptations to your aerobic base, your heart and lungs can take in and circulate more oxygen at higher workloads. Your muscles and tissues can extract and use the oxygen to generate energy aerobically.
The more efficient your aerobic system becomes, the faster and longer you can run without getting winded or needing to produce a significant percentage of energy from exhaustive anaerobic metabolism.
#2: Reduces the Risk of Injury
Running at an easier pace places less mechanical stress on your body, which helps reduce the risk of overuse injuries. When you slow down, the forces traveling through your muscles, tendons, bones, and joints decrease, giving your body a better chance to adapt to training.
At slower speeds, several subtle biomechanical changes occur. Your ground reaction force—the impact your body absorbs with each step—is generally lower, your stride length tends to shorten, and your overall loading rate decreases.
Together, these changes mean your tissues experience less cumulative stress with every stride.
Because running involves thousands of repetitive steps, even small reductions in impact can make a meaningful difference over time. Easy running allows you to build aerobic fitness and accumulate training volume while keeping injury risk lower, which is one of the key reasons it forms the foundation of the 80/20 training approach.
#3: Reduces the Risk of Overtraining and Allows You to Actually Run Fast
One of the primary problems with running in the middle zone—the moderately hard gray area between easy and hard—is that it’s not easy enough to allow your body to actually recover.
As such, runners who run their long and easy runs too hard are always flirting with the risk of overtraining because accumulated fatigue raises stress levels in the body. Let’s say a hard workout takes you from feeling 100% to 60%. A full recovery doesn’t occur unless you bounce back to nearly 100%.
If your recovery run the day after the hard workout is too fast or too intense, instead of recovering to 90-100% or so, you might recover only to about 80-85%.
This is problematic because it decreases potential performance and increases the risk of overtraining.
If you’ve only recovered to 80-85%, when it’s time to do the next hard speed workout, your body will already be starting at a reduced capacity–you only have 80-85% of your effort to give to the workout, instead of nearly 100%.
This means your ability to run as hard or as fast during the workout is impaired, which impedes your potential performance gains.
In practical terms, if you’re supposed to run 6 x 1,000 at your 10K pace but can only muster about five reps or fall five seconds off your pace for each interval, your body will not have as potent a training stimulus for inducing positive fitness adaptations.
By running your easy runs easily, you will have the strength and energy to maximize your hard workouts and nail the times you strive for. Studies show that polarizing training indeed improves running performance.
One study compared the effectiveness of four different training approaches for improving aerobic capacity (VO2 max) over nine weeks.2Stöggl, T., & Sperlich, B. (2014). Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Frontiers in Physiology, 5(33). https://doi.org/10.3389/fphys.2014.00033
The researchers divided 48 highly-trained endurance athletes (distance runners, cyclists, triathletes, and cross-country skiers) into one of four training programs: high-volume training, “threshold training,” high-intensity interval training (HIIT), or polarized training (which is akin to the 80/20 method of running).
Of the four approaches, the athletes in the polarized training group demonstrated the greatest increases in VO2 max, time to exhaustion, and peak velocity/power after nine weeks.
In addition to affecting performance, if you only recover to 80-85% after the first workout because you did your recovery run too hard, your second workout might set you back to 50% instead of 60%.
Then, if you again run too hard for your recovery, you might bounce back to only 75-80%.
Over time, you’re wearing yourself down and increasing the risk of overtraining.
#4: Helps Your Body Become More Efficient At Burning Fat
Slower running causes favorable adaptations in fat metabolism, allowing you to run faster while still burning fat for fuel rather than carbohydrates.
At lower exercise intensities, the muscles can burn fat to generate ATP (cellular energy) rather than relying more heavily on stored glycogen (carbohydrates).
Our bodies have a limited capacity to store carbohydrates in the form of glycogen, whereas even the leanest runners have enough body fat to fuel hours upon hours of exercise.
Running slowly helps your body burn fat more efficiently and spare glycogen, which can be hugely beneficial for marathoners as well as those looking to burn body fat.
How Can I Apply the 80/20 Method Of Running To My Training?
Again, the 80/20 method of running involves running easy for 80% of your mileage or minutes (depending on your preferred workout accounting) and running hard for the other 20%.
For example, if you run 30 miles per week (about 50 km), you will run 24 miles at an easy pace or easy effort, and 6 miles will be devoted to speed work.
Of course, it might not always be as simple as saying if you run five days a week, you should run four days easy and one day hard, as you may run a different number of days per week, where the math isn’t as neat.
Moreover, even if you run five days a week, you might have two hard workouts, but the mileage accrued during warm-ups, cool-downs, and recoveries counts on the “easy” side of the 80/20 rule, not the “hard” side.
So, if your workout is a 2-mile warm-up, 3 x 1-mile at 5K run pace with 400m between, and a 1-mile cooldown, you’ve run 3.75 miles easy and 3 miles hard.
How Slow Should Your Easy Runs Be?
Surprisingly, one of the hardest parts about following the run slow to run fast 80/20 method is actually running slow enough on the easy days.
We know the 80/20 method is that you need to run slow to run fast, but what is “slow”? How slow should your easy runs be?
The short answer is slow enough to feel really easy, which will probably feel impossibly slow at first.
Here are a few ways you can determine your pace for easy runs:
- 90-120 seconds per mile or 60-90 seconds per kilometer slower than your goal race pace goal pace
- A pace you can maintain where your heart rate is at 60-75% of your maximum heart rate
In terms of goal race pace, for example, if you are training for a 5K in 24 minutes (7:45 pace), your easy runs should be at 9:15-9:45 pace.
This method can be great for anyone who finds they aren’t performing as well as they think they should, given their training. There’s a good chance you need to run slower to run faster.
To help calculate your heart rate zones for low-intensity aerobic running, keep reading for our heart rate zone guide.
After starting to use the 80/20 principe as foundation for my training, I’ve come to realise that I’ve been training too intensive all my life. Declining performance, detoriation in the final stages of a race, and injuries are pretty easy attributed to age. However, after a nasty foot injury that kept me aside for a couple of months I restarted training according to 80/20. I was really (and am) struggling to run in lower zones. I trained for 10 weeks and saw my heart rate in z1 gradually stabilizing at 9.45 per km. This weekend I ran a 10k testrace and I managed to run at my threshold pace for nearly an hour. Not my best 10k ever, but certainly the best since years. And without detoriation. Moreover, I’m able to train 5 times a week without feeling exhausted all the time.