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The Benefits of Low-Intensity Running

Low-intensity running often gets a bad rap, considered by some as lazy or ineffective. However, the truth couldn’t be more different. Understanding the physiology and benefits behind this form of running is crucial for anyone looking to improve their distance running game.

Understanding Your Body’s Energy Systems

Sustained Aerobic Metabolism

During low-intensity runs—where you can maintain a comfortable conversation without snatching for breath every few words—your body primarily relies on sustained aerobic metabolism. Think of this like running on electric power in a hybrid car: it’s efficient and designed for sustainability over long distances. Your body taps into a mix of carbohydrates and body fat for energy, leaning more towards body fat as the primary source during these low-intensity activities. This approach trains your body to make better use of stored body fat as a lasting energy source.

High-Intensity Aerobic Metabolism

When your runs exceed the “conversational pace” measure—this could include tempo runs, threshold runs, sprints, or hill climbs—you are stepping into the realm of high-intensity aerobic metabolism. While it’s still under the aerobic umbrella, these activities tap more into your carbohydrate stores for that immediate burst of energy. It’s like engaging the turbocharger in your hybrid car: you’re still relying on its efficient engine but also drawing a bit more from the fuel tank for that extra push.

The Importance of Low-Intensity Running

Low-intensity running isn’t about laziness or inefficiency; it’s a tactical choice in your training regimen. Pushing the pace too hard can cause you to rely more on carbohydrates as your primary fuel source. This is counterproductive for endurance running, as it bypasses the valuable opportunity to train your body to use body fat for sustained energy efficiently. To stick with the car analogy, low intensity running increases the capacity of your battery.

Breathing Test: How to Know Your Intensity Level

A straightforward way to gauge if you’re maintaining a low-intensity pace is through the “Breathing Test.” If you can hold a conversation during your run, that’s the right pace. Imagine you’re having a phone conversation with another person, you’re able to talk but the other person can tell you’re exercising, then you’re hitting the mark. Five-word bursts between gasps do not qualify as a “conversational pace” and can lead to poor breathing, increased heart rate, and elevated cortisol levels—all of which are counterproductive to your goals.

The Principle of Minimum Dosage

The concept here is to apply the minimum effective dose of exercise needed to achieve desired outcomes. It’s not about training harder; it’s about training smarter. This ensures you make the most of each running session without compromising your long-term progress.

Avoiding “The Bonk” Through Efficient Fuel Use

One major advantage of training your body to be proficient in burning body fat for fuel is the ability to avoid “the bonk.” The term “bonking” refers to the state where you’ve depleted your carbohydrate stores and your performance declines sharply. Your body has a limited supply of carbohydrates stored in the muscles, liver, and bloodstream. Once these are used up, and if you haven’t been replenishing them through food or drink, you’re at risk of bonking.

In contrast, even lean athletes have thousands of calories worth of body fat available as fuel. By being efficient at using body fat, you can extend your endurance and run faster without having to worry about hitting that wall. It allows you the freedom to manage your effort well for extended periods—be it a long training run, an ultra-marathon, or multi-day events.

The 80/20 Rule: A Balanced Approach to Training

One of the most effective training paradigms is the 80/20 rule, which suggests that 80% of your total running time should be spent at low intensity and the remaining 20% at higher intensity. This ratio has been supported by numerous studies and is widely adopted by elite athletes in various endurance sports, not just running.

When you apply this 80/20 principle, you create a strong foundation of aerobic fitness. The 80% of time spent on low-intensity running helps your body become efficient at utilizing body fat as a fuel source, improves your aerobic capacity, and allows for better recovery.

The remaining 20% can be devoted to high-intensity training like tempo runs, threshold workouts, and intervals. This higher intensity work serves to improve your lactate threshold, VO2 max, and overall speed. However, it’s critical to separate these sessions from your low-intensity workouts, or to place them at the end of mixed sessions, to preserve the integrity of your low-intensity training.

Remember, violating the 80/20 rule by adding too much high-intensity work into your regimen can lead to overtraining, increase the risk of injury, and compromise the physiological benefits of your low-intensity runs.

Managing Intensity in Mixed Workouts

It might be tempting to include both high and low-intensity segments within a single workout session. However, it’s important to remember that the effects of high-intensity efforts can stay in the bloodstream for up to 30 minutes post-activity. This residual effect can actually turn what you intend to be low-intensity segments into high-intensity work, counteracting many of the benefits you’re aiming to achieve with the low-intensity portion.

For example, consider a 60-minute workout structured as follows:

  • 10-minute warm-up
  • 10 minutes at high intensity
  • 20 minutes at low intensity
  • 10 minutes at high intensity
  • 10 minutes at low intensity

Despite the low-intensity segments accounting for 30 minutes, the workout effectively becomes a high-intensity session due to the sustained physiological response from the high-intensity efforts.

To achieve an 80% annual training time of low-intensity running, be strategic in your workout planning. If you need to incorporate both low and high-intensity elements, consider performing the high-intensity segments at the end of the session. This ensures that the low-intensity work remains truly low-intensity and allows you to gain the associated benefits like fat-burning and aerobic efficiency.


The Importance of Terminology: Why We Say “Low Intensity” and Not “Slow”

As coaches, we place great emphasis on the words we use to describe different aspects of training. That’s why we prefer to use the term “Low Intensity Running” over alternatives like “long slow distance” or “Zone 2.” Here’s why this distinction matters:

  1. Removes Stigma: The term “slow” often carries negative connotations, making runners feel like they are not making sufficient progress. “Low intensity,” however, doesn’t come with that psychological baggage.
  2. Accurate Description: “Low Intensity” is both descriptive and precise. It provides a clear guideline on how to approach this style of training, emphasizing that lower intensity levels have their unique set of benefits.
  3. Avoids Confusion: If you’re not steeped in sports science literature or have not undergone specialized training, terms like “Zone 2” might not mean much to you. “Low intensity” is accessible and easily understood without requiring any background knowledge.
  4. Psychological Boost: Using the term “Low Intensity” can actually make you feel like you’re doing something purposeful and constructive. You’re not merely “running slow”; you’re strategically running at a lower intensity to reap specific physiological benefits.
  5. Highlights Individuality: The intensity of your run is relative to your own physical capabilities and current training status. By referring to it as “low intensity,” we emphasize that this is about your individual training parameters, not a collective or arbitrary standard.

Switching our vocabulary to “Low Intensity Running” can make a significant difference in how you perceive and benefit from this crucial component of your training.


Low-intensity running is a cornerstone of any well-rounded training program, especially for distance runners. It offers a sustainable way to train your body’s aerobic system, enabling you to become a more efficient runner. Incorporating this method into your routine is not just beneficial—it’s essential for those who want to excel in the long game.

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