Zone 2 training lays the foundation for your entire running training.
Nevertheless, “fitness gurus” across various fields, such as CrossFit and Hyrox fanatics, love to tell you that high-intensity interval training (HIIT) is superior to low-intensity training (LIT). Per minute, it is. And of course everybody wants to hear that because it’s contrarian and it saves time. But they miss the point that the body can handle a lot of LIT and not much HIIT. And not only that. The higher your low-intensity mileage, the more high-intensity training you can handle, such as VO2 max intervals, as we runners like to call it.
So, zone 2 training is the great enabler for spending more time in zones 3, 4, and 5.
What Zone 2 Training Actually Is
Zone 2 is the intensity just below your first lactate threshold, LT1. Lactate stays low, and you can still speak in complete sentences. An economist would say: zone 2 is great value. Even though zone 3 has a higher training effect and zone 1 a lower recovery cost, zone 2 hits the sweet spot of training stimulus and timely recovery. As a result, runners at all levels, from beginners to elite athletes, spend most of their mileage in zone 2.
Zone 2 vs. Recovery Running
Your base runs and most of your long runs are in zone 2. The intensity range is typically 60-75% of your VO2 max, although the higher end depends somewhat on your training level. Recovery runs, by contrast, are in zone 1 and therefore below 60% of your VO2 max. Recovery runs are also short, usually 40 minutes or less.
Zone 2 vs. Moderate Runs
Moderate running happens at the higher end of zone 2 and can touch zone 3, right around LT1, depending on your training level. That means moderate runs are still slower than marathon pace and can sometimes replace easy runs if you can recover. Just don’t make that a rule, as that’s a common fallacy among amateurs.
Zone 2 and FatMax
Not surprisingly, FatMax, the intensity where fat-burning peaks, also falls within zone 2. Although zone 1 uses a higher percentage of fat to fuel the effort, zone 2 burns more in absolute terms because it requires more calories. But that’s not the case for zone 3 and up, as the metabolism shifts increasingly to glycogen. Fitter runners hit FatMax at higher intensities.
Benefits of Zone 2 Training
It’s no coincidence that base training mostly consists of zone 2 training. It not only prepares you for upcoming training phases, but also helps you recover from past training blocks and racing.
Aerobic Development
Many intensities support aerobic development. Think fast intervals that increase your heart’s stroke volume or threshold runs that raise your lactate threshold. But zone 2 wins on scalability. You can handle far more of it than any other intensity, and that volume strongly affects capillarization, mitochondria, and oxidative enzymes.
Low Recovery Cost
The main advantage of zone 2 training is that the body can handle a lot of it. Zone 2 causes little muscle damage, doesn’t tap into glycogen stores much, and barely taxes your nervous system. Unsurprisingly, the base phase has the highest weekly mileage in some training systems. That also means if you want to increase your training volume to become a higher-level runner, start with more zone 2 training before adding more intensity.
More Resilient Legs
Heart and lungs adapt quickly to an increased training load. So do muscles. But connective tissues need more time to adapt because of limited blood supply. Bones also remodel more slowly than muscles. Gradually increase zone 2 training before adding intensity to protect your body from injury. Don’t trade quick fitness gains for injury.
Zone 2 Training Pace and Heart Rate
Several methods can help you determine your zone 2. For pace, enter a recent race result into a training pace calculator to get a training pace range to work with. Heart rate is less straightforward, since few people know their true HRmax. What’s more, the simple formula of percentage of HRmax discounts that different athletes have different resting heart rates.
Finding Zone 2 Heart Rate From Your LTHR
A reliable way to find your zone 2 range and the remaining zones is Joe Friel’s 30-minute time trial. After a 10-15 minute warm-up, run all-out for 30 minutes. Push the split button 10 minutes into the trial to get a clean average over the last 20 minutes of running. That average is your lactate threshold heart rate (LTHR). In Joe Friel’s system, zone 2 is 85-89% of LTHR. You can use it to set up your zone method in TrainingPeaks.
Monitoring HR Alongside Pace
Both pace and heart rate work for monitoring your easy zone 2 runs. But don’t expect them to align perfectly, as environmental conditions like rolling hills, wind, or heat can increase the effort required for the same pace. I consider pace the gold standard under normal conditions, but I recommend keeping your heart rate on your smartwatch display, too.
Understanding Cardiac Drift
You will also notice that your heart rate rises toward the end of medium-long runs and long runs. That’s because your body temperature rises slightly as the workout goes on, less efficient muscle fibers are recruited as your slow-twitch fibers fatigue, and fluid loss reduces blood plasma volume. You’ll notice this about 60 minutes into your run. As you get fitter, you’ll have less cardiac drift. I recommend accepting the upward drift of your heart rate and staying on pace during long runs, because it’s wrong to teach your body to slow down during longer efforts. Finish your long runs strong.
Zone 2 and Training Volume
Zone 2 may not be the most potent intensity, but it delivers a solid training stimulus with a low recovery cost. It is hard to climb the ranks of amateur running on low training volume, even if you’re endowed with great talent.
Training Frequency vs. Run Duration
You can increase your weekly zone 2 running mileage in 2 ways: lengthen your existing easy runs, including the warm-up and cool-down segments of key workouts, or add training days. The former is the obvious choice at first, since longer runs also have a stronger training effect. But once easy runs approach 60 minutes and regular long runs reach 120 minutes, you can double down on raising weekly mileage with additional runs. For amateurs, that might mean increasing your running frequency from 4 to 5 or 6 days, and for pros, it’s daily doubles.
When More Zone 2 Can Break a Plateau
More mileage in itself can make you faster. But the real leverage from higher mileage is that it increases your capacity to handle a higher training load in key workouts, such as tempo runs, threshold work, and VO2 max intervals. Successful runners keep around 80% of their weekly mileage in zone 1 and 2. That means whenever you increase easy mileage by, say, 10%, you can also increase running in zone 3 and up by the same percentage.
When More Zone 2 Isn’t the Answer
Throwing more mileage at stagnating times is not always the right call, though. That is often the case when a runner doesn’t have enough threshold and VO2 max work in the program, including a sensible week-to-week progression. Optimize your current mileage until further gains are hard to come by. Then, and only then, it makes sense to increase weekly mileage.
Common Zone 2 Training Mistakes
Unlike more intense training zones, zone 2 running isn’t terribly complex. No elaborate warm-ups, cool-downs, or interval manipulations. But 3 common pitfalls can trip you up.
Drifting Into Zone 3
For many runners, it is all too common to run supposedly easy runs in zone 3. While higher intensity brings a higher training stimulus, it also requires more recovery. That’s exactly where it jeopardizes your key running workouts. Zone 3 running has its place, but you need to schedule it strategically to allow enough recovery.
Treating Zone 2 as a Fixed Pace
Pace is your best guide in normal conditions. But on a hot day, into a headwind, or on a hilly route, the same pace costs more from the start. Slow down and let heart rate keep you in zone 2. That’s different from cardiac drift late in a long run.
Assuming Fasted Runs Are Better
Fasted runs carry some benefits, such as improved fat oxidation during the run and possibly greater mitochondrial adaptation. But social media often overstates it. There’s no real proof that fasted runs improve race performance. Morning runs before breakfast are generally ok as only liver glycogen depletes overnight, not muscle glycogen. Just be aware of the downsides of fasted running. Done often, it can slow recovery, increase muscle breakdown, and raise stress hormones.
Zone 2 Workouts
While zone 2 training offers little creativity beyond adjusting running duration, it covers a broad intensity spectrum. On good days, you can run closer to zone 3, and on tired days, you can border on zone 1 instead.
Base Runs
All zone 2 runs are easy runs, but not all easy runs are zone 2 runs. That’s because easy runs include all runs under the aerobic threshold (LT1), including zone 1 runs. Therefore, I refer to zone 2 runs as base runs here. They can range from 30 to 75 minutes, and it’s feasible for the same runner to do a 30-minute base run after a hard session but a longer run on rested legs.
Medium-Long Runs
Medium-long runs are basically extended base runs from 1:15 to 1:30 hours. A good placement is midweek, 2 days after a harder workout. You can also swap every other long run for a medium-long run. For 5K and 10K preparation, medium-long runs can replace true long runs. Assuming a zone 2 pace of 5:00 – 6:00 min/km for an upper-intermediate amateur runner, this covers 13 – 18 km and is therefore sufficient for those shorter race distances.
Standard Long Runs
Long runs start at 1:30 hours and can be as long as 3 hours during peak week in marathon preparation. While the long run can also take the format of progression long runs or long runs with a fast finish, the standard long run is run in zone 2 throughout. Since body heat and fatigue build up during long runs, it’s ok to allow a cardiac drift bordering zone 3 in the second half of the run. In other words, a higher heart rate without increasing the pace.
