You’ve likely heard of zone training, especially if you work out wearing a fitness watch.
Zones let you know how hard you are working and what energy sources are fueling your workout. You do not have to be only in one zone for the whole workout; cycling through zones will benefit your workout. Sometimes you have less time and want to work harder; sometimes, you have more time and want to work at a lighter intensity for longer. Using your heart rate is meant to be a guide to help you reach those goals while listening to your body.
How to calculate your heart rate training zone
To find your target heart rate and estimate which zone you are in, you need to know your maximal heart rate. The simplest estimate of maximum heart rate is 220 beats per minute (bpm) – your current age. Multiply that number by the percentage of your target heart rate zone.
Five Zones
Zone 1 is considered the target range for warm-up and recovery work and should be about 50-60% of your maximum heart rate (HR).
Zone 2 is considered the target range for aerobic and base fitness work and should be about 60-70/65 - 75% of your HR max.
Zone 3 is the range for aerobic endurance work and should put you at about 70-80% of your HR max.
Zone 4 is for anaerobic capacity, the limit of energy your body can produce using anaerobic means and should be about 80-90% of your HRmax.
Zone 5 is the target zone for short burst speed training and should be about 90-100% of your HR max.
The zones that get talked about the most by fitness experts are zone 2 and zone 5.
Zone 2 training, also known as endurance training, involves cardio performed at a relatively low intensity, steady state, for an extended period. Cycling, swimming, running, rowing, walking, or hiking all qualify—any activity you can maintain for well over 45 minutes to 3 hours.
How To Know When You’re in Zone 2
The easiest (and surprisingly accurate) way to determine if you’re in zone 2 is the “talk test.” In zone 2, you should be able to breathe entirely with your mouth shut if you’re not speaking. If you are speaking, it shouldn’t be pleasant. You can speak, but it's hard to.
The Health Benefits of Zone 2
Zone 2 is the highest level of exertion that is effectively pure mitochondrial phosphorylation before you start accumulating lactate,” explains an expert applied physiologist to Peter Attia on his podcast The Drive. To get the most benefits out of zone 2 cardio, you want to stimulate your mitochondria as much as possible by working in the higher end of your zone 2 range. Work too hard, and you’ll shift into zone 3—where you tap into glucose for energy, your blood lactate rapidly increases, and you stop stimulating your mitochondria.
Recent research has revealed that mitochondria play a key role in the aging process and most age-related diseases. Poor mitochondrial function is linked to heart disease, dementia, insulin resistance, type 2 diabetes, metabolic syndrome, and cancer.
Regular zone 2 training can contribute to a reduced heart rate (at rest and during exercise) and an increased VO2 max. Zone 2 training requires your heart, lungs, and blood vessels to work in unison to deliver oxygenated blood to your muscles. As your heart gets stronger, it becomes more efficient.
Zone 2 puts very little stress on the body compared to high-intensity activities or heavy strength training. It enables you to add volume to your training while lowering your risk of injury, overtraining, or fatigue.
Exercising in Zone 2 has been shown to improve stress resilience, mood, focus, and sleep and help ward off dementia.
The Health Benefits of Zone 5
On the other hand, Zone 5 training, also known as HIIT, is high-intensity or anaerobic threshold training that involves brief and powerful anaerobic bursts.
Heart rate zone 5 is your maximal effort. Your heart, blood, and respiratory system are working at their maximum capacity. Lactic acid will build up in your blood, and you won't be able to continue at this intensity after a few minutes.
Exercising at a higher intensity helps you maintain our fast-twitch muscle fibers. Zone 2 uses “slow-twitch” muscle fibers, which are preserved as we age. Fast-twitch fibers are not preserved.
After exercise, the body needs oxygen at a higher rate than before the exercise began. This sustained oxygen consumption is known as excessive post-exercise oxygen consumption (EPOC). During EPOC, the body is restoring itself to its pre-exercise state and thus is consuming oxygen at an elevated rate. This means you will burn more calories for hours after you stop exercising, hence bosting your metabolism.
Which leads to a popular question...which zone promotes fat burning and weight loss?
Answer: both! While zone 2 has been called the “Fat Burning Zone,” which is partly true, the claim that exercising exclusively in this zone is required for overall weight loss and fat loss is not valid. Zone 2 will burn a higher percentage from fat, but the total expenditure relative to higher zones will be less. If volume is equal, higher zones will ultimately burn more.
So, should you exercise in both zones? Yes. Both Zone 2 and Zone 5 are part of the weight loss and fitness equations. Also, remember that the actual time spent exercising takes up a small portion of the day. Your entire day’s activity should be considered when thinking about weight loss. Utilizing both forms of exercise is an idea as they complement each other effectively. The more time you spend within a zone, the more efficient you become. Work in a mix of heart rate zones for the best outcome to provide variety.
Fitness experts suggest:
Atakan, M. et al (2021). Evidence-Based Effects of High-Intensity Interval Training on Exercise Capacity and Health: A Review with Historical Perspective.
Rose, T. et al. (2020). Sprint and Endurance Training in Relation to Redox Balance, Inflammatory Status, and Biomarkers of Aging in Master Athletes.
Misrani, A. et al (2021). Mitochondrial Dysfunction and Oxidative Stress in Alzheimer’s Disease.
Christina Wilson
Author