Zone 2 running is having a moment. Every running influencer and longevity expert loves running in Zone 2. But why is it so valuable? And when is it NOT a good idea?
You can see the threshold for Zone 2 is when lactate levels begin to rise!
Disclaimer: I don’t think zone training is the best way of organizing your training as a runner.
That’s because we don’t race according to zone. Nobody has ever said, “I’m hoping to run my 5k at a Zone 4.8” or “My marathon was at a 3.7 Zone.” That doesn’t make any sense!
Even though running is a distance and pace-based sport (and you’re better off focusing on those metrics during training), zones can still provide a helpful framework for figuring out the intensity of some of your training sessions.
But runners have been using Zone 2 for decades. We just called it different things:
- LSD (Long, Slow Distance)
- Easy runs
- Recovery runs
- Conversational runs
- Base runs
- Shakeouts
- Fun runs
These names all describe a low effort intensity that helps us run more weekly mileage while not placing unnecessary stress on our bodies. It’s what allows us to build mileage while running difficult workouts.
But how do you know if you’re running in Zone 2?
What is Zone 2?
Zone 2 is defined as a steady physiological state where blood lactate levels are stable. This usually corresponds to about 60-75% of maximum heart rate.
For runners who like to rely on a Rating of Perceived Exertion (RPE), Zone 2 running is about a 4-5 on a scale of 1-10 (but note that RPE is more difficult for new runners since you have “fewer gears.” Are you a beginner? Just know that your “easy” may feel a little more challenging since you’re still building fitness!).
If you prefer to run by feel, Zone 2 running should be conversational, controlled, and comfortable. If you’re running with a friend, expect great conversation!
While Zone 2 is technically defined as one with stable lactate levels, we can also understand it as a pace. Zone 2 running is usually a pace that’s about 1.5 – 3 minutes per mile slower than your 5k race pace or 1.5 – 2 minutes per mile slower than your marathon race pace.
You can also use this handy pace chart based on half marathon finish times:
Zone 2 is part of the 5-zone system:
- Zone 1: very easy intensity that is considered “light exercise” with a heart rate of 50-60 percent of maximum
- Zone 2: easy intensity that is within about 60-70 (sometimes 75) percent of maximum heart rate
- Zone 3: moderate intensity that is within about 70-80 percent of maximum heart rate
- Zone 4: difficult intensity that usually corresponds to lactate threshold or 80-90 percent of maximum heart rate
- Zone 5: very difficult intensity that requires very hard exercise to reach 90-100 percent of maximum heart rate
- Zone 6: an all-out, maximum intensity sprint. This isn’t really a physiological zone but is often used to describe a max effort.
Running in Zone 2 should actually comprise the majority of your training volume. It’s easy enough to cause less impact force and mechanical stress (reducing your risk of running injuries) while also being intense enough to provide the physiological adaptations that we want as endurance athletes.
Because Zone 2 is a relatively easy effort, we need a lot of it to prompt the adaptations we need. This is why we run easy in Zone 2: to allow us to run more of it! In other words, a low-volume Zone 2 program won’t be very effective.
Zone 2 Running Benefits
There are a tremendous number of benefits to this zone of effort. In fact, it’s arguably the most important zone of them all!
Just think of what Zone 2 running does to your body. It…
Builds denser capillary beds. With a more robust network of capillaries surrounding your hard-working running muscles, your body will deliver more oxygenated blood and be able to work harder.
Creates mitochondria. We all know that mitochondria are the “energy factories of the cell.” But more of them is always a good idea! The more ATP that your mitochondria can produce, the more energy you’ll have for racing faster.
Builds a stronger heart. Zone 2 running can increase the stroke volume of your heart, leading it to pump more blood with every stroke.
Burns more fat. If your goals are weight loss, better body composition, or you’re training for a marathon or longer, you want to be as efficient as possible with fuel use. Being more fat-adapted is a big part of that!
Builds a bigger endurance base. This not only improves your general fitness but also makes more difficult sessions (like tempo runs or hill workouts) more manageable.
Clearly, there’s a lot to like about running in Zone 2.
But its an intensity that, by itself, isn’t enough to get you into peak shape. You’ll never reach your potential if you focus exclusively on Zone 2. While it’s important, there is immense value in other zones! This idea is discussed in more detail in my article for Outside Magazine.
Drawbacks to Running in Zone 2
The biggest drawback to Zone 2 is that it’s just one zone. No runner should spend all of their training in one intensity zone!
This is why the Maffetone Method is misguided. Too much time in any zone will limit your long-term progress.
One of Zone 2’s biggest benefits is also its biggest drawback. Because Z2 is low-intensity, it presents a lower risk of injuries.
But that also means it’s not intense enough to get you into peak shape!
Any runner who wants to improve and reach a new PR will want to spend time in zones 3, 4, and 5. We typically call these “workout zones” because they correspond to the effort of races at the marathon level and shorter:
- Zone 3 will likely include both your half marathon and marathon paces
- Zone 4 may include your 10k race pace (if it’s about 50:00 – 60:00)
- Zone 5 probably includes all race paces of 8k and shorter (sometimes 10k race pace if you’re more competitive)
Specificity is important in helping us reach our potential. Most training plans include race-specific workouts that help you prepare for the unique demands of the race that you’re training for.
Zone 2 won’t prepare you for the demands of racing, which almost always include higher heart rates than this zone (with the exception of some ultramarathons).
What About Zone 3?
Zone 3 has gotten a bad reputation recently. If you’ve read Daniels’ Running Formula, he might call it “gray zone” training.
Many think it’s too easy to give us a lot of fitness, but too difficult to run in during our easy runs. But it does have its place!
Beginner runners or those running low mileage programs can also spend more time in Zone 3 because their volume is relatively low (they probably won’t make as many adaptations without Z3). This zone is really only a problem when you spend too much time in it. Beginners, by definition, aren’t running a lot so this isn’t much of a concern.
If you’re a competitive, talented runner, you can probably afford to spend a good chunk of time during your base runs at this more moderate aerobic pace. You’re more economical so the stress of Zone 3 isn’t as much of a problem.
You can also run a Z3 workout – or “aerobic threshold run” – instead of simply spending more time at this moderate intensity during your base runs. For more details on Zone 3, aerobic threshold, and how to use this intensity during training, check out my interview with John Davis Phd for the Strength Running Podcast:
Just be cautious with too much Zone 3 running: if more than 40-50 percent of your overall volume is at this intensity, it may lead to an injury due to the extra mechanical stress and less overall recovery.
Zone 2 is One Piece of the Puzzle
Yes, Zone 2 is very important!
But no, you don’t have to strictly stay in Zone 2 all the time. In fact, there’s value in lower intensities like Zone 1 and higher intensity that include your half-marathon and marathon race paces (like Zone 3).
At no point should you exclusively run in Zone 2 or else you’ll leave a lot of fitness on the table. While there might be quite a few running influencers or longevity gurus expounding on the “magic” of Z2, it’s just one zone of many.
Longevity doctors in particular are not focused on your running performances. Instead, they’re focused on general health metrics and a desire to see you live a healthy, long live. That’s great but is distinct from that of a running coach who is focused on helping you race faster!
Ultimately, performance is what you should focus on:
- Instead of worrying about your VO2 Max score, build speed by improving your mile or 5k finish time.
- Instead of worrying about Zone 2, build endurance by improving your half-marathon or marathon finish time.
After all, a race performance includes every physiological metric you care about (Z2 threshold, lactate threshold, VO2 Max, running economy, etc.). If you’re improving your racing, then you’re improving all of these metrics!
We know this more well-rounded approach is better because that’s what the best runners in the world do. They train in a comprehensive and variable way that includes every zone of effort.
We also know this is a better approach because extreme training programs come and go as fads:
- CrossFit Endurance is too intense and doesn’t include much Zone 2 running
- Maffetone Method isn’t intense enough and only includes Zone 2 running
At Strength Running, we don’t support fads. We support best practices.
For training that follows best practices, consider a custom running plan or training program to help you reach your goals!
