Whether your goal is to win a half-marathon or simply complete a 5K without walking, there’s good reason to make Zone 2 running the cornerstone of your training plan.
Zone 2 runs are the type where you’re going easy enough to participate in a conversation. But, not so easy that you can deliver a lengthy monologue without huffing and puffing.
This training approach — where you’re logging steady runs at 60-70% of your maximum heart rate, or in Zone 2 — allows you to maintain a low-intensity effort for an extended period of time without feeling overly fatigued by the end.
And many experts consider it the sweet spot between making training adaptations and minimizing injury risk.
The concept of “run slow to run fast” has been a foundational training approach for decades. But, it’s currently exploding in the running community. The reason partly is due to the bandwidth given to it by public figures such as longevity-expert Dr. Peter Attia and world-class endurance coach Dr. Iñigo San Millán (whose athletes include 2-time Tour de France winner Tadej Pogačar).
As buzzy as the concept is, it’s also rife with ambiguity. Between my own experiences and the latest research on Zone 2 running, here’s why and how you should make Zone 2 running the cornerstone of your training plan.
Why Trust Us?
I’m a long-time professional runner (I’ve run a 2:30 marathon and 1:09 half marathon), State Champion high school running coach, and running book author on my chronicles solo running for 12 months over 22 countries.
I have a lot of insight on the advantages of Zone 2 running as an athlete, coach and author.
What Is Zone 2 Running?
Zone 2 refers to one of the five widely-accepted exercise heart rate zones. While experts may differ slightly on the nuances of each classification, Cleveland Clinic illustrates the concept like this:
- Zone 1: Low to moderate intensity exercise at 50-60% of your maximum heart rate. This utilizes fat as the primary fuel source. It includes warm-ups, recovery runs, and cooldowns
- Zone 2: Moderate intensity exercise at 60-70% of your maximum heart rate. This utilizes fat as the primary fuel source. Included in classic base-building and easy running.
- Zone 3: Moderate to high intensity exercise at 70-80% of your maximum heart rate. It utilizes a combination of fat, carbohydrates, and protein to supply fuel. Included in sustained efforts like tempo runs.
- Zone 4: High intensity exercise at 80-90% of your maximum heart rate. This utilizes carbohydrates and protein as primary fuel sources. Included in lactate threshold work.
- Zone 5: Very high intensity exercise, at 90-100% of your maximum heart rate. This utilizes carbohydrates and protein as the primary fuel sources. Included in anaerobic work and max effort training.
This means if your maximum heart rate is 190 bpm, your Zone 2 is going to be between 114 and 133 bpm.
Related: How Runners Should Use Heart Rate Training
What’s So Special About Running in Zone 2?
The idea of beneficial Zone 2 training is far from new.
You’ve probably heard of either the “talk test.” (Is your effort such that you can carry a conversation?) Or even the Long Slow Distance philosophy. This from with famed New Zealand coach Arthur Lydiard and which emphasizes heaps of easy miles.
Running coach and podcaster Jason Fitzgerald offers the clearest explanation I’ve heard yet: “Zone 2 is often considered the lowest intensity that produces meaningful training adaptations.”
While Zone 1 has its place — warmups, cool downs, recovery jogs within workouts, super long efforts, and such — but, it doesn’t produce the adaptations to the extent that higher zones do.
What about Zone 3? Which is 70 to 80% of your max heart rate.
Zone 3 helps to develop your fast-twitch muscle fibers and ability to work in oxygen-deprived conditions (anaerobic).
This all makes you better at short-term sprinting but doesn’t improve long-term endurance.
Plus, training a lot in Zone 3, you run the risk of overworking and ultimately overtraining, studies show. Experienced and elite athletes tend to better equipped to handle more Zone 3 work than newer and more recreational athletes. However, the possibility of overdoing it always lurks even for the elite.
For the bulk of your miles, Zone 2 is the sweet spot.
Research shows Zone 2 running primarily develops slow-twitch muscle fibers. They are very efficient at using oxygen to generate more fuel (ATP) for continuous muscle activation over a long period of time.(Aka, your endurance).
Zone 2 running does more than just make you better at long runs. It may seem counterintuitive but running slow can contribute to faster times. A 2021 study in The Journal of Strength & Conditioning Research found that tempo runs and easy runs had the most impact on overall running performance compared to interval sessions.
The authors note the easy runs were particularly beneficial “partly because of [their] contribution to total distance run.”
The more miles you’re able to run, the more efficient you’ll become at it over time.
In short: Zone 2 running is an efficient way to lay a solid and sustainable foundation of fitness with a lower risk of over-training or injury. And the longer you stay injury-free, the more consistently you’ll be able to build your muscular and aerobic base.
Other Benefits of Zone 2 Training for Runners
Zone 2 training offers a cascade of benefits for endurance athletes such as runners, cyclists, and swimmers outside of endurance performance.
According to Dr. Loward Luks, an orthopedic surgeon, sports medicine specialist, and the author of “Longevity… Simplified” these benefits include:
- Lower resting heart rate
- Decreased blood pressure
- Lower risk of injury
- Improved insulin resistance
- Improved endurance
- Improved performance in Zones 4 and 5
- Improved longevity
Dr. Luks explains that Zone 2 training also promotes an increase in your total number of mitochondria, the mitochondrial efficiency, and your metabolic health and flexibility.
lAl of these contribute to better overall health. And, a greater chance of living longer in addition to being able to run for very long distances.
How Long Should Your Zone 2 Runs Be?
Exactly how much time per week you spend in Zone 2 depends on your total mileage, typical pace, and running experience (more on that in a minute).
The most common recommendation is to aim to run for at least 45-60 minutes. This time is valuable in order to reap all the training adaptations Zone 2 has to offer.
Without deliberately shooting for that range, my easy runs (including doubles) are all a minimum of 45 minutes.
The high school runners I coach — many of whom come to me with no experience — work their way up to 45 minutes in one go. Over the course of the season, they build up to a maximum of 70-75 minutes.
How Can I Find My Personal Zone 2?
The Simple Conversation Test
The simplest (but also least-scientific) way to tell if you’re in Zone 2 is by judging your effort based on your breathing pattern and ability to talk:
If you can contribute to a conversation without getting winded and you’re primarily breathing through your nose, there’s a good chance you’re working in Zone 2.
If you’re struggling to string full sentences together or breathing mostly out of your mouth, you’re probably working in Zone 3 or above.
The Highly-Precise Lactic Acid Test
The most complicated — but also most precise — way to know where exactly you transition into and out of Zone 2 is to get a lactic acid test. These are primarily performed in laboratory settings but can also be self-administered if you know what you’re doing. They offer a real-time opportunity to see the points at which you transition from one training zone to another.
Lactic tests can shed a lot of light on your training. But for the purposes of this article, if you get tested, your focus should be understanding the threshold at which you transition from the aerobic work and fat oxidation of Zones 1 and 2 to the higher intensity and increasingly anaerobic work of Zones 3 and up.
The Goldilocks Approach: Calculating Your Heart Rate Zones
Somewhere in the middle of easy and precise lies simply doing the math to find your personal heart rate zones.
By now, you know that Zone 2 running requires you to be within 60-70% of your maximum heart rate. Here’s how you figure that out:
- Test or calculate your maximum heart rate. The best way to do that is by doing an exercise stress test or VO2 max test in a lab. If that’s not possible, you can use this simple calculation to get a rough estimate:
220 – your age = max heart rate
- Identify your resting heart rate. If you don’t have a wearable that feeds you this information, take your pulse manually via your wrist or neck. Your resting heart rate is simply the number of times your heart beats in one minute. It’s best to measure this right when you wake up in the morning, before getting out of bed.
- Find your heart rate reserve. This number describes the difference between your maximum heart rate and your resting heart rate. You can find it with this equation:
Max heart rate – resting heart rate = heart rate reserve
- Calculate your target heart rates for each of the 5 zones. Multiply your Heart Rate Reserve by the percentage of Max Heart Rate that corresponds with each range. 50%-60% or 0.5-0.6 for Zone 1, 0.6-0.7 for Zone 2, 0.7-0.8 for Zone 3, 0.8-0.9 for Zone 4, 0.9-1.0 for Zone 5. Then, add your resting heart rate to each of those ranges. For Zone 2, it looks like this:
[Heart rate reserve x 0.6] + resting heart rate = Minimum Zone 2 heart rate
[Heart rate reserve x 0.7] + resting heart rate = Maximum Zone 2 heart rate
You’re left with the target range to keep your heart rate within to train in Zone 2.
Once you know your own Zone 2 range, you can monitor it during or after runs by way of a heart rate monitor. Ideally a chest strap, which tend to be more accurate than wrist-based trackers.
Why Is It so Hard to Run (and Stay) in Zone 2?
In theory, spending lots of time training in Zone 2 should be simple. You can take it relatively easy, catch up with your friends if you’re a social runner, and end feeling accomplished but not exhausted.
In practice, it’s hard for many athletes to follow through on their intentions to mostly hover in Zone 2. That’s because:
- Running slower and longer requires discipline and restraint. Especially in those moments when you’re feeling good and eager to speed up or keep up with someone else.
- It requires continual awareness of how hard you’re working to make sure you’re staying in your personal target range. It can also be easy to sneak into Zone 3 territory toward the end of a run without realizing it.
Personally, I know how easy it is to get carried away while either chatting with my husband and training partner or daydreaming about an upcoming race. One moment, I’m feeling smooth and relaxed and running in the right range. The next, my pace creeps down before I know it. I see a similar tendency in my high school athletes, who gravitate to the same groups for easy runs, and who love seeing improvements in pace via their GPS watches.
If you catch yourself breathing harder than you should, or find yourself facing hillier sections than you’re ready to handle, you’ll need to slow down — possibly to the point of walking.
Maintaining a Zone 2 effort for most runs can be challenging. But, it’s well worth the effort when you consider the many benefits you stand to gain.
The Best Way to Work Zone 2 Runs Into Your Training Plan
I’ve run a lot of races in my career, including multiple Olympic Trials, and a lot of my training, even if unintentional, has followed one of the most popular approaches to Zone 2 training: It’s called the 80/20 Rule where roughly 80% of your training occurs in Zones 1 and 2 and the other 20% occurs in Zones 3 and above.
This is one application of polarized training, a varied training approach where your plan incorporates a mix of high-volume, lower-intensity training, threshold training, and high-intensity interval training.
When following the 80/20 Rule, the foundation of your training is easy running (mostly in Zone 2), with harder efforts sprinkled within.
Looking back at old marathon training logs, my mileage — like many of the pros I’ve run against — has often loosely followed the 80/20 Rule, give or take a few percentage points.
One example: In one of my last big weeks before the 2020 Olympic Marathon Trials, I ran 100 miles. Of those, 17 were hard and high-quality — one workout of 2 x 2 miles, 2 x 1 mile, and 2 x 800; and one 10-mile tempo immediately after an easy 10 miler. The other 83 miles were just comfortable.
Without me even realizing it, that week and many others surrounding it were guided by the principles of polarized training and the (roughly) 80/20 Rule.
Among the high school runners I coach, their training leans toward a similar breakdown as well. A typical week of the fall cross country season consists of two workouts, such as 3 x 1 mile and a 4-mile tempo. Given that most of my varsity runners float around 30 miles per week, this puts them at 77/23, so within a few percentages of the 80/20 Rule too.
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