Running Slow to Race Fast: The Science Behind Easy Runs

As runners, we’ve all heard the mantra: “You’ve got to run slow to run fast.” 

Every seasoned runner recognizes that not all runs should—or can—be a race against the clock. Those lung-busting intervals and sweat-drenched tempo runs are vital for driving improvements in speed, stamina, and race-day prowess. 

But what underpins the success of these intense sessions?… 

The unsung hero of a well-rounded training plan: the humble, easy run.

Despite the obvious benefits, many runners choose to push their easy runs. 

Maybe you feel easy runs provide less benefit? Perhaps it’s external pressure… when you look at your Strava feed, you might feel the silent pressure to push yourself more on each run, aiming for Kudos and Course Records. And before you know it, that planned easier run has turned into a semi-tempo effort, or even a race effort, to get that CR. 

But chasing speed for digital accolades will become a roadblock to true athletic progress.

In this article we’re going to address that by taking a look at:

• Why easy runs are important: physiological benefits and how they lay the foundations for more intense training.
• Best ways to control the pace/effort of an easy run: pace, heart rate, perceived effort.
• How much training should be easy/low intensity.

Why Such an Emphasis on Easy Runs?

As we’ll discuss shortly, there’s a number of physiological benefits to easy runs. Yet, at the most basic level they form the backbone of your training plan — setting a framework that ensures you have the base conditioning to handle and recover from harder training sessions, reducing injury risk and aiding in your long term progression.

Physiological Benefits of Easy Running:

Running at an easy pace isn’t just about recovery from harder sessions, or logging miles. There’s a wealth of science behind the ‘slow burn’ of easy runs. When you maintain a low-intensity pace, several physiological adaptations and benefits occur:

1. Increased Myoglobin Levels:

Myoglobin is a protein found within your muscle cells — particularly slow twitch (type I) muscle fibers. It plays a vital role in drawing oxygen from your blood to your muscles.

The volume of easy runs is a key stimulus for increasing myoglobin levels within your slow-twitch fibers. And more myoglobin means more oxygen getting to your muscles, leading to enhanced performance and recovery. 

2. Capillary Development

Easy runs stimulate the growth of new capillaries in muscles. With more capillaries, there’s improved oxygen delivery and waste removal, contributing to increased endurance.

3. Mitochondrial Development

Mitochondria are your cells’ aerobic powerhouses. They produce ATP, the primary energy molecule in the body, through aerobic respiration.

Boosting your mitochondria count leads to improved energy production and efficiency during exercise, and enhanced recovery during and after exercise.

Large volumes of low intensity training is an important factor in increasing the volume of mitochondria within slow twitch muscle fibres.

4. Strengthening of Ligaments and Tendons:

Our ligaments and tendons adapt slowly to the stresses of running.

Easy runs, being low in intensity, allow these tissues to adapt and strengthen over time, reducing the long-term risk of injury. This is why it’s important to build a strong aerobic base before building upon it with more intense training.

5. Enhanced Running Economy/Efficiency:

Running economy refers to the amount of oxygen used to run at a given pace. There are three effective methods that improve running economy and all should be implemented if you want to maximise your training:

1. Low intensity training
2. High intensity training
3. Strength training

By incorporating easy runs, you can improve your running economy consistently overtime. This means you use less energy and oxygen at the same pace. In essence, you become a more efficient runner, allowing you to run at a faster pace at any given intensity. 

Easy runs are also vital for gaining the benefits from harder training sessions…

Building the Foundation: How Easy Runs Elevate Intervals and Tempo Workouts

Every seasoned runner knows that not every run can or should be a hammerfest. Intense sessions like intervals and tempo runs are vital for improving speed, strength, and race performance. 

But what fuels the effectiveness of these sessions? 

The answer: the solid base built through consistent easy runs.

1. Aerobic Foundation:

Easy runs predominantly tap into the aerobic energy system. Over time, consistent easy running strengthens this system, expanding your aerobic capacity. 

The result?… A robust aerobic foundation that allows you to handle greater volumes of faster-paced workouts. 

You will also recover more efficiently between hard efforts, be it during interval repeats or between intense training days.

2. Enhanced Muscle Adaptation:

The consistent and repetitive motion of easy running aids in refining muscle memory. When it comes time to switch gears into faster sessions, your muscles are primed and familiar with the act of running, allowing for smoother transitions to higher intensities.

3. Improved Running Economy:

As discussed, easy runs enhance your running economy. An improved running economy means that during those tempo sessions or intervals, your body can perform at a high intensity with a reduced energy cost. Essentially, you can run faster with the same effort.

4. Injury Prevention:

The strengthening of ligaments and tendons during easy runs means that when you push the envelope during a hard session, your body is more resilient. Making it more equipped to handle the stress, reducing the risk of overuse injuries that can arise from intense workouts.

5. Mental Resilience:

Never underestimate the mental aspect of training. Easy runs, especially the longer ones, help in building mental stamina and resilience. This mental conditioning proves invaluable during the tough segments of an interval or tempo session, where pushing through barriers becomes critical.

6. Active Recovery and Glycogen Replenishment:

Easy runs can serve as an active recovery, promoting blood flow and aiding in faster muscle repair. Moreover, these runs support efficient glycogen replenishment, ensuring you’re fueled and ready for the next hard session.

So, how fast should easy runs be?

The Ideal Pace for Easy Runs

For those already well-acquainted with the world of running, the term ‘easy run’ is familiar. 

That said, many runners don’t run their easy runs ‘easy’. Often, what they class as easy is actually more of a ‘steady’ or ‘semi-tempo’ effort. Whilst that might get you some extra kudos, it’s taking away from the true purpose of an easy run. 

So what is the true purpose of an easy run? 

Not only, will this reduce the risk of injury and overtraining, but it will ensure you’re sufficiently recovered—physically and mentally—to get the most from your harder training sessions.

Defining the intensity or pace of an easy run can sometimes be tricky. What’s easy one day, may feel more of an effort the next. For that reason it’s helpful to consider a few factors when controlling intensity:

1. Controlling Easy Runs By Feel

Foremost, an easy run should feel comfortable. You should be able to hold a conversation without gasping for breath. While your legs may feel fatigue from previous training, the intensity should not feel difficult or challenging.

If we were to quantify this using the RPE scale, where 0 is at rest and 10 is maximum effort, easy runs should typically fall in the 2-4 range. So, if you find yourself huffing and puffing, slow down.

2. Using Heart Rate Zones

If like me you train with a heart rate monitor, your easy runs should typically be around 65-75% of your maximum heart rate.

Training at low intensity ensures that you’re working aerobically, just below the point where blood lactate levels begin to rise above baseline levels.

An important point to note here is: for trained runners, the Karvonen Heart Rate formula is considered to be a much more effective way to set heart rate zones. You can read more about calculating heart rate percentages using the Karvonen heart rate formula here.

One big advantage with using heart rate is that you can use this to monitor progress. For instance, if you keep your heart rate the same during your easy runs, and then find find you’re running faster at the same heart rate, that’s a clear indication that you’re becoming more efficient at that intensity.

3. Controlling Easy Runs by Pace

Many experienced runners find their easy pace is anywhere from 1:00 to 2:00 per mile slower than their current 5k race pace. To give a percentage range, this typically falls between 50-75% of your 5k pace, or 55-80% of your 10k pace. Remember, this is a general guideline and can vary based on the individual. Not sure how to calculate a percentage of your 5k pace — click here to view the easy run pace chart based on 5k time.

One point to note is that pace targets are based on relatively flat terrain and should be adjusted when running on different gradients. Here it can be useful to set your watch to display average pace across your run.

We can also include recovery runs and easy/moderate pace runs (provided its kept below tempo effort) as part of what we consider easy mileage. The table below gives an idea of RPE, Heart rate and pace for recovery, easy and easy/moderate runs.

	Recovery Pace Run	Easy Pace Run	Easy/Moderate Pace Run (Just below steady/tempo)
RPE	2 out of 10	3-4 out of 10	4-5 out of 10
Heart Rate	60-70% MaxHR*	65-75% MaxHR*	70-80% MaxHR*
Pace	50-60% of 5k Pace, 55-65% of 10k Pace	55-70% of 5k Pace, 60-75% of 10k Pace	65-75% of 5k pace, 70-80% of 10k Pace

*Using the Karvonen formula is generally considered more effective for trained athletes.

Using the combined cues from RPE, heart rate, and pace can help to ensure you’re hitting the sweet spot for your easier runs.

What Percentage of Your Training Should Be Easy?

Here’s where it gets interesting. For most well-trained runners, a surprising 70-80% of total running volume should be at an easy pace. So, the vast majority of your miles should be easy. This percentage can rise to as much as 90% amongst elite runners. 

This allows for recovery, aids in avoiding overtraining, and paves the way for those harder workouts (like intervals, tempos, and long runs) to be truly effective.

Most times the following rules apply:

• The day before and after a hard training session (interval, tempo, long run etc) should be an easy run, recovery run or rest day.
• Your weekend, or mid-week, long run, should be at an easy, or easy/moderate pace – unless you’re in a race specific phase of Marathon or Half-Marathon training.
• Your warm-up/warm-down before interval training should be at an easy pace.
• If completing double training days, then normally one or both of these would be easy, or easy/moderate.

In Conclusion:

While it might be tempting to push the pace on every run, especially when you’re feeling strong, the benefits of easy runs shouldn’t be overstated. By embracing the “slow and steady” mantra for a significant portion of your training, you’re laying a robust foundation for athletic growth and improved running performance. 

Embracing the benefits of easy runs ensures a holistic approach to your training. Helping to maximize both health and performance outcomes.

So next time you lace up those shoes, remember: sometimes, to run fast, you’ve truly got to run slow. Happy training!