Heart rate zones turn a number on your wrist into something you can train by. In endurance sports like running and cycling, most systems split effort into five zones, Zone 1 through Zone 5, so you can see how hard you are actually working and choose the right intensity for the session in front of you.
Zones are personal. They can be built from your maximum heart rate, your resting heart rate, or your lactate threshold heart rate, depending on the method behind them. That is also why the zones on one device can differ from the zones on another.
At a Glance
- Heart rate zones turn effort into a scale you can train by, most commonly Zone 1 through Zone 5.
- Each zone serves a different purpose, from recovery and aerobic base work through to near-maximal efforts.
- Zones can be set from maximum heart rate, heart rate reserve, or lactate threshold heart rate, and each method draws different boundaries.
- Devices show different zones because they use different methods, different settings, and different ways of measuring heart rate.
- Check your zones against your breathing, your perceived effort, and how long you can hold each intensity.
What Are Heart Rate Zones?
A heart rate zone is a range of intensity defined by your heart rate in beats per minute (BPM). The five-zone model is the most widely used, running from Zone 1 up to Zone 5 as effort climbs from easy movement toward near-maximal work. Three-zone and four-zone models also exist, built on different thresholds for different training purposes.
Heart rate, breathing, and overall physiological stress all climb together as intensity rises. That is what makes zones useful for more than a snapshot of effort. They tell you whether the intensity you are holding actually matches the purpose of the session.
What Do the Different Heart Rate Zones Mean?
The five-zone model splits heart rate into Zone 1 through Zone 5. Each zone sits at a different level of intensity and does a different job in your training. Here is what each one feels like and where it is normally used.
Zone 1: Recovery and Low-Intensity Training
Zone 1 is typically used for warm-ups, cool-downs, and recovery sessions. Breathing should feel very easy, and the overall training load is low, making it possible to keep moving for a long time without much strain. For example, after a high-intensity interval workout, easy movement in Zone 1 can help you gradually recover without adding much additional training stress.
Zone 2: Aerobic Endurance Training
Zone 2 is a common low-intensity zone for endurance training. The effort feels relatively easy, with steady breathing that you can maintain for an extended period. It’s often used for easy runs, long runs, and other aerobic base training. Over time, this type of training helps your body adapt to sustained exercise and improve its ability to maintain aerobic effort for longer periods.
Zone 3: Tempo and Steady-State Training
Zone 3 is more demanding than easy aerobic training. Your breathing becomes noticeably faster, but you can generally maintain a steady effort for a reasonable amount of time. Zone 3 can be used for steady-state runs, sustained moderate-intensity workouts, and some easier tempo runs. For runners, this type of training can help build the ability to maintain a faster pace for longer.
Zone 4: High-Intensity Training Around Lactate Threshold
Zone 4 generally represents a high level of training intensity and, in some heart rate zone models, includes intensities around the lactate threshold. Breathing becomes noticeably harder, and the effort is no longer as easy to sustain as Zone 2. However, you can still train in this zone through sustained runs or longer intervals. Zone 4 is commonly used for threshold workouts, higher-intensity tempo runs, and longer intervals to help runners improve their ability to maintain performance at high intensities.
Zone 5: High-Intensity and Near-Maximal Effort
Zone 5 generally corresponds to exercise intensity close to your maximum heart rate. Breathing is very heavy, and the effort can only be maintained for a relatively short period. It’s commonly used for VO₂ max intervals, short high-intensity repeats, and some sprint workouts. These sessions provide a strong cardiovascular and high-intensity stimulus, but they also place a greater amount of stress on the body, so adequate recovery is especially important.
How Are Heart Rate Zones Calculated?
There are several ways to calculate heart rate zones. The most common methods use Maximum Heart Rate (Max HR), Heart Rate Reserve (HRR), or Lactate Threshold Heart Rate (LTHR) as the basis for setting your zones.
% Maximum Heart Rate
The maximum heart rate method is one of the simplest ways to calculate heart rate zones. It uses a percentage of your maximum heart rate to define each training zone.
Your maximum heart rate can be estimated using an age-based formula, such as the familiar “220 − age,” or determined through maximal-effort exercise testing, field testing, or laboratory testing. Age-based formulas are convenient, but individual differences can be significant, so the result may not accurately reflect your actual maximum heart rate.
In a common five-zone model, the following percentages of maximum heart rate can be used as a general guide:
| Heart Rate Zone | % Maximum Heart Rate |
|---|---|
| Zone 1 | Approx. 50–60% |
| Zone 2 | Approx. 60–70% |
| Zone 3 | Approx. 70–80% |
| Zone 4 | Approx. 80–90% |
| Zone 5 | Approx. 90–100% |
For a deeper look at maximum and resting heart rate, see Know Your Max and Resting Heart Rate.
% Heart Rate Reserve
The Heart Rate Reserve (HRR) method takes both maximum heart rate and resting heart rate into account, making it more personalized than simply using a percentage of maximum heart rate. However, the accuracy of the resulting zones still depends on having reliable maximum and resting heart rate values.
First, calculate your heart rate reserve:
HRR = Maximum Heart Rate − Resting Heart Rate
Source: American Society for Preventive Cardiology Clinical Practice Statement
You can then use the Karvonen method to calculate your target heart rate:
Target Heart Rate (THR) = Resting Heart Rate + (% Intensity × HRR)
Source: University of Minnesota
For example, if your maximum heart rate is 190 BPM and your resting heart rate is 50 BPM, your heart rate reserve is 140 BPM. At 70% intensity, your target heart rate would be:
50 + (0.7 × 140) = 148 BPM
% Lactate Threshold Heart Rate
The Lactate Threshold Heart Rate (LTHR) method uses the heart rate associated with your lactate threshold as the reference for setting training zones. Lactate threshold can be thought of as a key point where, as exercise intensity increases, blood lactate begins to accumulate at a faster rate. It provides an indication of how well your body can sustain higher exercise intensities.
The most direct approach is a graded exercise test in a laboratory, where blood lactate is measured at different exercise intensities and the lactate threshold is identified from the resulting curve. You can also estimate LTHR through structured field tests, such as a 30-minute Time Trial.
One advantage of using LTHR to set heart rate zones is that it ties training intensity more closely to your individual threshold performance. However, the exact testing protocol and zone boundaries can vary depending on the training system being used.
Why Are My Heart Rate Zones Different on Different Devices?
If your heart rate zones look different across watches, apps, or training platforms, it does not necessarily mean one of them is wrong. The differences usually come down to three things: how the zones are calculated, the personal data used in the calculation, and how heart rate is measured.
- Different calculation methods and zone boundaries: One device may work from maximum heart rate, another from heart rate reserve or lactate threshold heart rate. Even on the same method, boundaries and algorithms differ. Some systems use three-zone or four-zone models built on physiological thresholds such as lactate threshold or ventilatory threshold, so both the number of zones and their edges can change from device to device.
- Inaccurate maximum or resting heart rate settings: If either value is set incorrectly on your device, every zone it calculates inherits that error.
- Different heart rate measurement methods: Wrist-based optical sensors estimate heart rate from changes in blood flow under the skin, while chest straps read the electrical signals produced by your heart. When intensity changes quickly, the two respond at different speeds, so the reading at any given moment can differ slightly, and so can the zone your device shows.
In short, the first two factors move the boundaries of your zones. The third moves the heart rate that gets recorded against them.
How to Know If Your Heart Rate Zones Are Right
You can’t tell whether your heart rate zones are accurate by looking at the numbers on your watch alone. It’s also important to consider how you actually feel and perform during your workouts.
Pay Attention to Breathing and Perceived Effort
If your device shows that you’re in Zone 2 but you’re already struggling to catch your breath, your zone settings may need a second look. Likewise, if a workout classified as high-intensity Zone 4 feels easy from start to finish, your heart rate zones may not be aligned with your actual effort.
If you want a better understanding of how your intensity changes during a workout, Suunto ZoneSense uses heart rate data to identify changes in exercise intensity, helping you see whether your actual effort matches the heart rate zone you’re targeting.
Combine Heart Rate with Pace or Power
If you can maintain the same pace at a lower heart rate over time, or run faster at the same heart rate, it generally indicates that your aerobic fitness is improving. Using a Suunto sports watch to track heart rate, pace, and training history can help you monitor these changes over time. During workouts, pairing it with a heart rate belt can also provide more responsive and consistent heart rate data.
Otherwise, heart rate does not respond instantly to changes in exercise intensity. During short intervals lasting only a few dozen seconds, your effort may already be very high even though your heart rate has not yet reached Zone 5. For short intervals, heart rate alone may not tell the whole story, so it’s best to consider pace, power, and perceived effort together.
Use Workout Duration as a Guide
Lower-intensity zones like Zone 1 and Zone 2 should generally be sustainable for longer periods, while Zone 4 and Zone 5 are typically much harder to maintain for extended periods. If how a zone feels and how long you can sustain it consistently differ significantly from what the zone is supposed to represent, it may be worth taking another look at your maximum heart rate, resting heart rate, lactate threshold heart rate, and the zone model your device uses.
Takeaways
Heart rate zones are a moving target. As your fitness, maximum heart rate, resting heart rate, and lactate threshold shift, the zones built on them need revisiting too. Read them alongside training load, pace, power, and perceived effort, and heart rate stops being a number you glance at and becomes a tool you train with.
