The Ultimate LSD Run Guide: Long Slow Distance Running, Explained

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One of the great ironies in running is the concept of running slow to get faster

Sure, it’s easy to understand how speed workouts, strides, hill sprints, and tempo runs can help you run faster over time, but the same can’t really be said about doing really slow runs at a jogging pace. It’s just not intuitive.

However, running coaches and distance runners have been incorporating long slow distance (LSD) runs in training programs for decades at this point.

Indeed, the LSD run has been, and continues to be, a staple, bread-and-butter workout for most distance runners focusing on anything from the 5k to marathon and beyond.

With that said, many runners grapple with reconciling the counterintuitive nature of LSD running and getting faster. They worry that running slow will indeed make them slow.

In this article, we will discuss LSD running, the benefits of the LSD run, and how to use LSD training to run faster.

We will cover: 

  • What Is LSD Running?
  • A Brief History of LSD Training
  • Why Should Your Long Runs Be Slow?
  • How Does LSD Running Make You Faster?
  • How Slow Should Your Long Slow Distance Runs Be?
  • How Long Should LSD Runs Be?

Let’s jump in!

A person running an LSD run.

What Is LSD Running?

Let’s get one thing straight right out of the gates: Although countless runners have made the joke that LSD running is like a good “trip”—playing on the shared name with the psychedelic drug—the LSD run has nothing to do with drugs or acid, or even lactic acid!

LSD running stands for long slow distance running. 

LSD running might also be called LSD training, and the workout itself is referred to as an LSD run.

Unsurprisingly, the long slow distance run, or LSD run, is exactly what it sounds like it would be: a long distance run performed at a slow, relaxed pace. 

Although doing a long run at a slow pace sounds simple enough to execute, maximizing the benefits of running LSD runs involves considering factors such as your fitness level, exercise heart rate, target race distance, and goal pace when deciding how slow and how long your LSD runs should be.

A person running an LSD run.

A Brief History of LSD Training

There are several conflicting theories about who invented the idea of long slow distance running. 

Some say the runners like Arther Newton, who ran at the turn of the twentieth century, was the first to implement LSD runs into his training plan.

Other people say that German athletic trainer and physician, Ernst van Aaken, is the founder of the concept of LSD running.

However, most people agree that running coach Joe Henderson was the first to coin the term long slow distance running, or LSD running, in 1969, and to popularize LSD running in mainstream endurance training programs.

Building upon the ideas of the great Arthur Lydiard, who popularized the idea of polarized training, which also plays into the idea of doing your fast runs fast but your easy runs really slow, coach Joe Henderson popularized the idea that running slow could actually make you faster.

People running in a park.

Henderson recommended LSD running as an alternative to the mainstream training methods for distance runners that he termed the “PTA school of running—the pain, torture, and agony” approach. 

Moreover, Henderson said that LSD runs aren’t only about getting faster, but they are also about enjoying your running. 

In this way, Henderson said LSD running isn’t for recreational runners as much as it is for competitive runners.

In his book, Long, Slow Distance, Henderson wrote, “LSD isn’t just a training method. It’s a whole way of looking at the sport. Those who employ it are saying running is fun – all running, not just the competitive part which yields rewards.” 

Why Should Your Long Runs Be Slow?

The entire concept behind the LSD run is that your long run needs to be run slowly, but why is that? What is the purpose of running your long runs at a slow pace?

To answer this question, it’s easiest to look at the downsides of running your long runs too fast. 

Doing a long run is inherently taxing on your body because you’re on your feet for a long time, using your muscles continuously for a couple hours, stressing your bones and joints, elevating your heart rate and respiration rates without reprieve, increasing your body temperature, and depleting your glycogen stores.

A person running in a park.

The faster you do this run, the higher the intensity and the greater the stress on your body.

If you run your long run at your goal race pace, or worse—faster—you are significantly taxing your body. 

Since most people do a weekly long run, it becomes easy to understand how this could quickly lead to overtraining, burnout, or injury, especially in the context of the overall training week, which likely includes other difficult workouts like intervals and tempo runs.

The primary objectives of the long run are to increase endurance, increase blood volume, help your body adapt to higher mileage and a longer time of your feet, and develop your aerobic base.

Long runs strengthen the cardiovascular system.

As the heart gets stronger, stroke volume increases, enabling the heart to pump more blood—and thus oxygen—out to the body every time it beats. This can effectively reduce heart rate because the heart becomes more efficient.

Capillary density increases, allowing for better perfusion of working muscles, and blood volume increases over time. 

A person running on the side of the road.

These adaptations, in turn, also increase stroke volume, cardiac output, oxygen transport and delivery, and, ultimately, VO2 max

Long runs also increase the mitochondrial density in skeletal muscles, particularly in Type I muscle fibers, and improve your ability to burn fat for fuel (rather than stored glycogen) at higher intensities.

Essentially, long runs build your physical and mental strength and stamina, and improve your aerobic fitness. 

It’s unnecessary to run your long runs at race pace, or anywhere right around race pace, to induce these goals. In fact, as mentioned, doing so can increase the risk of injury and overtraining, and it significantly increases your recovery time.

Rather, running your long runs at a slow, easy pace effectively accomplishes the intended goals of the long run while also protecting your body from overtraining and burnout by reducing the stress imposed on the body.

In this way, you can think of the primary benefit of LSD running is that the LSD accomplishes the goals of doing long runs while minimizing the damage to your body as much as possible.

The Ultimate LSD Run Guide: Long Slow Distance Running, Explained 1

How Does LSD Running Make You Faster?

Long slow distance runs have the major benefit of decreasing recovery time relative to long runs completed at or near race pace, or even your regular training pace.

In this way, you can still reap all the performance and aerobic benefits of a long run with a LSD run while hastening your recovery time. 

This means you can bounce back faster after your weekly run and recover quickly for your next hard workout.

If you’re better recovered and rested for your speed workouts, you can attack them with more intensity, thus reaping more benefits from greater improvements.

This concept is exactly what Arthur Lydiard meant by polarizing your training: by doing your slow runs easy, you can do your speed workouts hard, which ultimately is the best way to get faster.

Polarizing your training also prevents the risk of injuries.

When you run at vastly different paces, rather than the roughly same pace for every run day in and day out, your stride length and cadence change because your speed changes.

As your biomechanics change, your muscles, bones, joints, and connective tissues are subjected to different stresses, loads, and forces.

This variety reduces the risk of overuse injuries compared to running at the same pace all the time because stress and strain on any one tissue is repetitive.

A person running on the beach.

How Slow Should Your Long Slow Distance Runs Be?

So, how slow is “slow” in LSD running? 

In general, most coaches say you should do your LSD runs at an easy pace that is at least 1–3 minutes per mile slower than a runner’s 10k pace for shorter races (10k and half marathon), or at least 1-2 minutes per mile slower than marathon pace for marathoners.

For example, if you want to run a marathon at 9:30 min/mile pace, you would want to do your LSD runs at 10:30-11:30 pace. 

For those more comfortable with kilometers, run your LSD runs about 50-90 seconds slower per kilometer. 

If you are using heart rate training, LSD runs should be performed in zone 2, or around 60-70% of your maximum heart rate.

Two people running on a path.

How Long Should LDS Runs Be?

The ideal length of your long slow distance runs depends on your fitness level, race distance you’re training for, and where in your training program you are.

Most beginning marathoners will work up to several 20-mile training runs per training block. Other coaches suggest approaching running LSD runs by having the total time on your feet for your longest long runs equaling your goal race time.

Gradually build up the length of your long runs over the course of your training block.

Remember, when it comes to long runs, slowing down can indeed make you faster, so embrace the LSD run and watch your times improve.

To add some speed intervals to your workouts during the week, check out our interval running guide here.

People running in a park.
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Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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