The Science of Finding Your Zone 2 — A Guide to Precision

Everyone has heard about heart rate zones and the idea that you should run in different zones depending on the type of race you’re training for.

For long distances, one of the most important zones is Zone 2. In every article I’ve read, Zone 2 is highlighted as the foundation for building aerobic capacity.

Zone 2 running is important because it builds your aerobic base, improves fat metabolism, enhances overall endurance, and helps you run longer with less fatigue over time.

Most training plans you’ll find online incorporate Zone 2 running in about 70%-80% of the workouts. These plans typically don’t specify heart rate zones but instead include runs labeled as “easy runs,” “long runs,” or “recovery runs.” In most cases, you can interpret these as Zone 2 runs.

If you need to spend 80% of your training time in Zone 2, how do you determine what Zone 2 is for you?

Based on Max Heart Rate

The simplest method is to use a running watch that measures your heart rate and can estimate your maximum heart rate. For example, a Garmin watch can calculate your max heart rate through the following process:

1. Start with a light warm-up for 10–15 minutes.
2. Gradually increase effort over the next 5–10 minutes until you reach a sustained, hard level.
3. In the final stage, perform a short sprint or an intense uphill run to reach your absolute maximum heart rate.
4. Make sure you are in good physical condition to attempt this, and for the best accuracy, use a chest strap monitor.
5. Finish with 5–10 minutes of easy running to cool down.

The data collected during this test will allow your watch to calculate your training zones accurately. Once you know your max heart rate, the general rule is that:

Zone 2 corresponds to 60%–70% of your maximum heart rate.

Using Math

If you read articles online, many suggest a mathematical formula to estimate your maximum heart rate:

MHR = 220 — your age

Then, to find your Zone 2 range, multiply your MHR by 0.6 and 0.7.

How Accurate is This?

I’m not entirely sure how precise this formula is. To better understand, I’ll calculate my Zone 2 using all of these methods and compare the results.

The MAF Method

The MAF (Maximum Aerobic Function) method, developed by Dr. Phil Maffetone, is a heart-rate-based training approach designed to improve aerobic capacity while reducing the risk of overtraining. It emphasizes training at a heart rate that optimizes fat-burning and endurance, forming a solid aerobic base essential for long-term performance gains.

To calculate your MAF heart rate, use the formula 180 minus your age, and adjust based on your fitness and health history:

• Subtract 5 if you’re recovering from illness, injury, or have been training inconsistently.
• Add 5 if you’ve trained consistently for more than two years without injuries or setbacks.
• Keep the value unchanged if you are generally healthy but have less than a year of consistent training.

All aerobic workouts should be done at or below your MAF heart rate to maximize fat metabolism, improve endurance, and avoid the stress associated with high-intensity workouts.

Using the Threshold Heart Rate

Personally, I find the threshold heart rate method the best way to determine Zone 2. This method accounts for running experience and form, which makes it more personalized compared to calculations based solely on maximum heart rate or age.

To find your threshold heart rate, take the average heart rate from a recent 10k race or a similarly hard effort. Unlike a single max value, this is derived from multiple data points during the effort. Once you have your threshold heart rate, calculate your Zone 2 range as:

75%–85% of Threshold heart rate.

This approach provides a more accurate reflection of your current fitness level and helps tailor your training to your unique capabilities.

Time to Compare

I spent a few minutes determining my maximum heart rate using my Garmin watch. According to Garmin, my maximum heart rate is 188 bpm, and it also lists a Lactate Threshold Heart Rate (LTHR) of 165 bpm.

• Based on max heart rate (60%-70%): 112–131 bpm
• Simple math (220 — age): 220–49 = 171; Zone 2: 103–120 bpm
• The MAF method: 180–49 + 5 = 136; Zone 2: ≤136 bpm

Looking at these values, I can tell you that I usually run at around 138 bpm, but running under 130 bpm would essentially mean walking. This is why I’ve been eager to figure out a more realistic way to determine a Zone 2 range that makes sense for my running pace.

Let’s take my most recent race as an example. It was a relay race, and my segment was 10.5 km — long enough to use the average heart rate from the race as a reliable data point.

Using this average heart rate, I calculated the Zone 2 range as 75%-85% of the average:

Average heart rate: 130–148 bpm, a range much closer to my regular runs and to the heart rate recorded during those runs.

Conclusion

The worst method of determining Zone 2 is undoubtedly the 220 — age formula. This approach is overly simplistic and ignores critical factors such as your running experience, fitness level, and individual physiology.

Using the heart rate from a 7–10k race to predict can be a much better method for determining a realistic Zone 2 range. This interval allows you to run at an effort that aligns with 80% of your weekly mileage while staying in the aerobic zone, without having to reduce your pace to an unnatural level.

Happy running, and may you always find the right Zone 2 for your goals!

If want to find out how Zone 2 can improve your Half Marathon, you can read one of my previous posts:

How I Shaved Nearly 3 Minutes Off My Half Marathon Personal Best