What are heart rate training zones?
Heart rate training zones are intensity ranges, expressed as percentages of a person's maximum heart rate (MHR) or heart rate reserve (HRR), that correspond to different physiological and metabolic states during exercise. The most widely used system divides exercise into five zones, from very light effort (Zone 1) to maximal effort (Zone 5). Exercise physiologists and sports coaches use zones to prescribe training at the correct intensity for a given physiological adaptation, such as aerobic base building, lactate threshold improvement, or maximal power development.
Training zone frameworks are used by organisations including the American College of Sports Medicine (ACSM) and are central to structured endurance training plans for runners, cyclists and other aerobic athletes. Zone-based training allows athletes and exercisers to match the intensity of each session to a specific goal rather than training at a single undifferentiated effort level. The five-zone model is the most common in endurance sports, though some systems use three, six or seven zones depending on the application.
The five heart rate training zones
The table below shows the five-zone model as commonly defined using percentage of maximum heart rate (%MHR) and percentage of heart rate reserve (%HRR, the Karvonen method). Zone boundaries vary slightly between different organisations and coaches; the values below are representative of widely cited exercise physiology references.
| Zone | Name | % Max HR | % Heart Rate Reserve | Primary Adaptation |
|---|---|---|---|---|
| Zone 1 | Active recovery / very light | 50-60% | 50-60% | Recovery, basic aerobic conditioning |
| Zone 2 | Aerobic base / light | 60-70% | 60-70% | Fat oxidation, mitochondrial density, aerobic endurance |
| Zone 3 | Aerobic / moderate | 70-80% | 70-80% | Aerobic capacity, cardiovascular efficiency |
| Zone 4 | Threshold / hard | 80-90% | 80-90% | Lactate threshold, race pace adaptation |
| Zone 5 | Maximal / all-out | 90-100% | 90-100% | VO2 max, neuromuscular power |
Fox formula vs Tanaka formula: estimating maximum heart rate
Accurate heart rate zones depend on a reliable estimate of maximum heart rate (MHR). The most widely known formula is the Fox formula (220 minus age), which has been used in clinical and fitness settings since the 1970s. The Fox formula was not derived from a rigorously controlled primary research study; it was an approximation based on observed data. A commonly cited limitation is that the standard error of this estimate is approximately plus or minus 10-12 beats per minute for an individual, meaning personal MHR can differ substantially from the formula's prediction.
In 2001, Hirofumi Tanaka and colleagues published a meta-analysis in the Journal of the American College of Cardiology examining data from 351 studies involving over 18,000 subjects. The Tanaka formula -- 208 minus (0.7 times age) -- was reported to have a standard error of approximately plus or minus 7.1 beats per minute, notably lower than estimates for the Fox formula. The Tanaka formula also showed a weaker age-sex interaction, suggesting it may be more consistent across sexes than the Fox formula. Exercise physiology texts frequently cite both formulas, with the Tanaka formula often noted as slightly more accurate for healthy adults.
The Karvonen method: using heart rate reserve
The Karvonen method, developed by Finnish physiologist Martti Karvonen and published in 1957, calculates target heart rates using heart rate reserve (HRR) rather than raw maximum heart rate. HRR is calculated as maximum heart rate minus resting heart rate. The target heart rate at a given intensity percentage is: resting HR + (intensity fraction x HRR). For example, to find the lower boundary of Zone 2 (60% HRR) for a person with a resting HR of 60 bpm and MHR of 190 bpm: 60 + (0.60 x 130) = 138 bpm.
The Karvonen method is considered by many exercise physiologists to better reflect individual cardiovascular fitness than simple percentage of MHR, because it accounts for resting heart rate -- which varies considerably between individuals and decreases with aerobic training. A highly trained endurance athlete may have a resting HR of 40 bpm, which produces significantly different target zones from a sedentary person with a resting HR of 80 bpm, even if their maximum heart rates are identical. The ACSM includes the Karvonen method in its guidelines for exercise prescription.
Zone 2 training: the science of aerobic base building
Zone 2 training -- sustained aerobic exercise at 60-70% of MHR or HRR -- is associated with improvements in mitochondrial density, fat oxidation capacity and aerobic base. At Zone 2 intensity, the body primarily uses aerobic metabolism, relying on fat and a smaller proportion of carbohydrate as fuel. Exercise physiologists have studied Zone 2 as the intensity at which fat oxidation and mitochondrial adaptations can be sustained for prolonged periods without significant lactate accumulation.
Research by Seiler and colleagues examining the training distribution of elite endurance athletes has described a polarised pattern in which athletes spend the majority of training volume at low intensities (broadly corresponding to Zone 1-2), a smaller proportion at high intensities (Zone 4-5), and relatively little at moderate intensities (Zone 3). This model -- sometimes called polarised training -- has been studied in comparison with threshold-focused training approaches. The rationale is that low-intensity volume builds aerobic capacity and mitochondrial function, while high-intensity bouts develop VO2 max and lactate threshold.
How to find your personal heart rate zones
The most accurate way to determine individual maximum heart rate and training zones is through a graded exercise test (GXT) administered by an exercise physiologist or sports medicine professional, often with concurrent measurement of gas exchange (VO2 max test). Laboratory testing can identify ventilatory thresholds that correspond more precisely to physiologically meaningful zone boundaries than age-based formulas.
For most recreational exercisers and athletes without access to laboratory testing, formula-based estimates combined with a heart rate monitor provide a practical alternative. The Tanaka formula (208 minus 0.7 times age) or the Fox formula (220 minus age) can be used to estimate MHR, and zones calculated as percentages of this estimate. Given the individual variability in MHR predictions, zones should be treated as starting estimates and adjusted based on perceived exertion and training response over time.
Câu hỏi thường gặp
What is Zone 2 heart rate training?
Zone 2 heart rate training refers to sustained aerobic exercise performed at 60-70% of maximum heart rate (or 60-70% of heart rate reserve using the Karvonen method). At this intensity, the body primarily uses aerobic fat oxidation, and the effort is sustainable for extended periods without significant lactate buildup. Zone 2 is associated with improvements in aerobic base, mitochondrial density, and fat oxidation capacity, and forms the foundation of many endurance training programmes.
Which maximum heart rate formula is more accurate: Fox or Tanaka?
The Tanaka formula (208 minus 0.7 times age) is generally considered slightly more accurate than the Fox formula (220 minus age) for healthy adults. A 2001 meta-analysis by Tanaka and colleagues in the Journal of the American College of Cardiology, based on over 18,000 subjects across 351 studies, reported a standard error of approximately plus or minus 7.1 bpm for the Tanaka formula. The Fox formula's standard error has been cited at approximately plus or minus 10-12 bpm. Both formulas provide estimates with meaningful individual variability, and laboratory testing remains the most accurate method.
What is the Karvonen method for calculating target heart rate?
The Karvonen method calculates target heart rate using heart rate reserve (HRR), which is maximum heart rate minus resting heart rate. Target HR = resting HR + (intensity fraction x HRR). For example, at 60% intensity with a resting HR of 65 bpm and a maximum HR of 185 bpm: 65 + (0.60 x 120) = 137 bpm. This method is considered to account better for individual cardiovascular fitness levels than simple percentage of maximum heart rate, and is included in ACSM exercise prescription guidelines.
How many heart rate training zones are there?
The most common model divides training intensity into five zones, corresponding roughly to 50-60%, 60-70%, 70-80%, 80-90%, and 90-100% of maximum heart rate. Some systems use three zones (easy, moderate, hard), while others use six or seven zones for more granular training prescription. The five-zone model is widely used in endurance sports and is consistent with frameworks cited by ACSM and major sports coaching organisations.
Can I use a heart rate monitor to train in zones?
Yes. A heart rate monitor -- whether a chest strap or a wrist-based optical sensor -- can be used to monitor training intensity in real time relative to calculated heart rate zones. Chest-strap monitors are generally more accurate than wrist-based optical sensors, particularly at high exercise intensities. Once maximum heart rate is estimated using a formula or laboratory test, target zone boundaries can be entered into most fitness watches or training apps to guide effort during sessions.
What is the difference between %MHR and %HRR zones?
Percentage of maximum heart rate (%MHR) zones are calculated as a fraction of maximum heart rate alone. Percentage of heart rate reserve (%HRR) zones use the Karvonen method, factoring in resting heart rate. For a given percentage target, %HRR zones will produce higher absolute heart rate values than %MHR zones for the same individual. Many exercise physiologists consider %HRR zones to be a more individualised prescription, particularly for people with notably low or high resting heart rates.
Tài liệu tham khảo
- Tanaka H, Monahan KD, Seals DR. "Age-predicted maximal heart rate revisited." Journal of the American College of Cardiology, 2001;37(1):153-156.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. 11th ed. Wolters Kluwer, 2022.
- Karvonen MJ, Kentala E, Mustala O. "The effects of training on heart rate; a longitudinal study." Annales Medicinae Experimentalis et Biologiae Fenniae, 1957;35(3):307-315.
- Seiler S, Tønnessen E. "Intervals, thresholds, and long slow distance: the role of intensity and duration in endurance training." Sportscience, 2009;13:32-53.
- Fox SM, Naughton JP, Haskell WL. "Physical activity and the prevention of coronary heart disease." Annals of Clinical Research, 1971;3(6):404-432.
- Thomas DM, Bredlau C, Bosy-Westphal A, et al. "Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model." Obesity, 2013;21(11):2264-2271.