The standard model uses five heart rate zones, each defined as a percentage range of your maximum heart rate. This is the system built into most fitness watches, gym equipment, and training apps. But depending on your goals and experience level, you might encounter models with as few as three zones or as many as seven.
The 5-Zone Model
The five-zone system is by far the most common. Each zone represents a band of intensity based on your estimated maximum heart rate:
- Zone 1 (50% to 60%): Low to moderate intensity. This is a casual walk or very easy warm-up. Your body relies almost entirely on fat for fuel, but the effort is too light to drive major fitness gains on its own.
- Zone 2 (60% to 70%): Moderate intensity. A brisk walk or easy jog where you can still hold a conversation. This zone has gained popularity for its role in fat burning and metabolic health, and it’s characterized by high rates of fat oxidation with minimal depletion of your stored carbohydrates.
- Zone 3 (70% to 80%): Moderate to high intensity. A steady run or vigorous cycling pace. Breathing gets heavier and talking becomes harder. Your body starts shifting from fat toward carbohydrates as its primary fuel.
- Zone 4 (80% to 90%): High intensity. Think tempo runs, hard interval efforts, or race-pace cycling. You can only sustain this for shorter periods, and speaking more than a few words at a time feels difficult.
- Zone 5 (90% to 100%): Maximum effort. All-out sprints or the final push in a race. You can hold this for only seconds to a couple of minutes before exhaustion sets in.
This five-zone breakdown aligns closely with what the American Heart Association recommends, though the AHA simplifies things even further: moderate intensity falls at roughly 50% to 70% of max heart rate, and vigorous intensity at 70% to 85%.
The 3-Zone Model
Endurance coaches often use a simplified three-zone model built around two physiological thresholds. The first threshold is the point where your breathing noticeably increases but you can still talk. The second threshold is the point where talking becomes nearly impossible and lactate builds up rapidly in your muscles.
Zone 1 sits below that first threshold, Zone 2 falls between the two thresholds, and Zone 3 is everything above the second. This model is the backbone of “polarized training,” a strategy where athletes spend roughly 80% of their time in Zone 1 and the remaining 20% in Zone 3, largely skipping the middle. Research on elite endurance athletes has found this distribution effective for building both aerobic base and top-end speed.
The 7-Zone Model
Competitive cyclists and triathletes sometimes train with seven zones, a system developed by exercise physiologist Andrew Coggan. This model is anchored to your functional threshold power (the highest effort you can sustain for about an hour) rather than heart rate alone. It splits the intensity spectrum more finely, adding distinct zones for lactate threshold work, VO2 max intervals, anaerobic capacity efforts, and very short neuromuscular sprints lasting just a few seconds.
Seven zones exist because, as Coggan put it, that’s the minimum needed to represent the full range of physiological responses in competitive cycling. For most recreational exercisers, this level of detail isn’t necessary. But if you train with a power meter or follow a structured race plan, the extra granularity helps you target very specific energy systems within a single workout.
How to Find Your Zones
Every zone model starts with knowing your maximum heart rate. The simplest estimate is 220 minus your age. A more refined formula, developed by researcher Hirofumi Tanaka, uses 208 minus 0.7 times your age. In practice, both formulas can be off by several beats per minute. A study of marathon runners found that the 220-minus-age formula underestimated max heart rate in men by about 3 beats and both formulas overestimated it in women by roughly 5 beats. If precision matters to you, a supervised maximal exercise test gives a more accurate number.
Once you have your max heart rate, you multiply it by the percentage range for each zone. For example, if your max heart rate is 185 and you want Zone 2 boundaries, you’d calculate 185 × 0.60 = 111 and 185 × 0.70 = 130. Your Zone 2 would be 111 to 130 beats per minute.
Heart Rate Reserve for Better Accuracy
A more personalized method uses heart rate reserve, sometimes called the Karvonen method. You subtract your resting heart rate from your max heart rate to get your reserve, then apply the zone percentages to that number and add your resting heart rate back. This accounts for individual differences in fitness. Someone with a resting heart rate of 55 and someone with a resting heart rate of 75 will get meaningfully different zone ranges, even if their max heart rate is identical. The Cleveland Clinic notes that this approach is generally more accurate than using a straight percentage of max heart rate.
Why Zone 2 Gets So Much Attention
Zone 2 has become a fitness buzzword, often promoted as the ideal intensity for building mitochondria (the structures inside your cells that produce energy), improving insulin sensitivity, and enhancing your body’s ability to burn fat. The appeal is real: Zone 2 exercise keeps metabolic stress low, preserves your carbohydrate stores, and can be sustained for long periods without excessive fatigue. A 10-week study of people with type 2 diabetes found that Zone 2 training increased the activity of mitochondrial enzymes.
That said, the evidence strongly favors higher intensities if your primary goal is maximizing mitochondrial adaptations. Zone 2 is valuable as the foundation of a training plan, not as the entire plan. Most exercise scientists recommend a mix of intensities, with Zone 2 making up the largest share of total training time and higher-intensity work filling in the rest.
Which Model Should You Use
For most people, the five-zone model is plenty. It’s what your fitness tracker already uses, it’s intuitive, and it covers the full range from easy recovery to all-out effort. If you’re training for a marathon, triathlon, or cycling event and want to fine-tune your workouts around specific thresholds, the three-zone or seven-zone models offer more precision. The zones themselves aren’t magic boundaries. They’re convenient labels for a continuous spectrum of effort, and your body doesn’t flip a switch the moment you cross from one zone to the next. What matters most is that you vary your intensity: spend most of your training time at an easy, conversational pace and reserve a smaller portion for genuinely hard efforts.