We all know exercise is good for us. Physical activity — even short bouts of it — can offer both immediate and long-term benefits, including reduced feelings of anxiety, lower blood pressure, improved sleep and a reduced risk of chronic disease.
That's why any exercise is better than no exercise. But intensity and duration also matter, especially if you have certain fitness goals in mind, such as losing weight, building muscle or training for a race or competition. Like weights are to strength training, your heart rate during cardio is a measure of how hard your heart's working to pump and deliver oxygen-rich blood to your muscles.
Heart rate zones help categorize this intensity based on your age and fitness level and indicate what energy source your body is using for fuel, says Taylor Samale, a senior health fitness coordinator at Houston Methodist.
"Knowing your target heart rate zones can be really helpful to help you train smarter, not just harder," says Samale. "Whether you're an athlete or someone looking to better their fitness, heart rate zones help ensure your workouts are matching your goals. You don't have to go all out all the time and be completely out of breath for your workouts to be successful."
Samale explains the benefits of each zone, how to know which zone you're in and which ones you may want to train based on your goals.
The 5 heart rate zones, explained
There are five heart rate zones, ranging from 1 to 5, that represent specific percentages of your maximum heart rate, which is age-determinant. Each zone corresponds to different intensity levels, benefits and energy sources. The higher the zone, the more intense, higher the heart rate and more carbs and protein that are being used as fuel versus fat.
Zone 1
Zone 1 is easy and is just above your resting heart rate, about 50 to 60 percent of your maximum heart rate.
"This is where you want to be just before and immediately following a workout," Samale says. "In this zone, you could carry on a full conversation easily, even sing if you wanted to, but you're definitely moving, increasing blood flow throughout the body and slightly elevating the heart rate."
Zone 1 is especially important after intense workouts, as you'll want to keep some movement going in order to flush the blood throughout the body, she adds. Plan on setting aside 5 to 10 minutes of your workout for cooling down in zone 1.
"It's not good to go from a zone 5 to stopping completely," Samale says.
(Related: If You're Not Cooling Down After a Workout, You Should Be — Here's How to Get It Done)
Zone 2
Zone 2 is light to moderate intensity at 60 to 70 percent of your maximum heart rate.
"You're definitely working, and you're feeling heat building up in your body. You might be lightly sweating, but you can still carry on a conversation and talk in full sentences," Samale says. "If you were on the phone with somebody, they might hear you breathing just a bit harder than normal, but no problem talking otherwise."
The goal of zone 2 is to build your aerobic base (endurance) and to train your body to use more fat for fuel instead of carbs, says Samale.
Zone 3
Zone 3 is moderate to high intensity at 70 to 80 percent of your maximum heart rate.
"Not all, but a lot of group fitness glasses tend to be mostly in zone 3, where you're breathing hard for most of the class," says Samale. "You can still talk in zone 3 but only in very short sentences. You definitely can't have a full-on conversation."
It's also sometimes called the "no man's land" zone, per Samale. Whereas zone 2 helps increase endurance and zone 4 helps with speed and power, zone 3 can sometimes feel goalless, she says. However, zone 3 does have a place, namely for endurance athletes.
"Say you're doing a race. If you're aiming for a specific time, you can't really worry about your heart rate the whole time," Samale says. "So, sometimes training in that uncomfortable spot in zone 3 up to zone 4 for a longer period of time can help you not only physically but mentally prepare for a race or whatever competition you may be doing."
Zone 4
Zone 4 is hard effort at 80 to 90 percent of your maximum heart rate. You'll barely be able to speak, likely only able to say one or two words before having to catch your breath again.
"Zone 4 is very beneficial in short bursts," says Samale. "You don't want to focus all of your exercise here, but doing the right amount of zone 4 is going to help improve your speed, power and anaerobic threshold."
The anaerobic threshold is the level in which your body needs more energy than what oxygen can provide and thus turns to the carbohydrate reserves in your muscles (glycogen) for fuel, creating lactic acid as a byproduct. Going past this threshold is what can contribute to exercise fatigue and forces your body to slow down.
On the aerobic side of things, zone 4 can also help increase your VO2 max — the highest amount of oxygen your body can utilize during an intense workout.
"The higher your VO2 max is, the more endurance you're going to have, the faster you're going to recover and the better overall cardiovascular health you'll have," says Samale. "While it's arguably more important to build your aerobic base at zone 2, for athletes or those looking to increase their speed and endurance for a race, it can be worth focusing on improving your VO2 max."
(Related: Is Lactic Acid Buildup Really What Causes Muscle Soreness After a Workout?)
Zone 5
Zone 5 is maximum effort at 90 to 100 percent of your maximum heart rate.
"In zone 5, you're going all out," says Samale. "You definitely won't be able to speak, and you're only going to last about a minute or less in this zone before you have to slow down."
Like zone 4, zone 5 can also increase your VO2 max and anaerobic threshold, per Samale.
How to calculate your target heart rate zones
There are two main ways you can calculate your target heart rates: the maximum heart rate method, which uses a simple age-based formula; and the more personalized Karvonen Formula or heart rate reserve method, which also takes into account your resting heart rate. Let's go over both.
In either method, you need to know your maximum heart rate, which is roughly 220 minus your age. It'll look something like this:
- 220 – your age = your max heart rate in beats per minute (BPM)
For example, the maximum heart rate of a 30-year-old would be around 190 BPM (220 – 30 = 190 BPM).
From there, you'll multiply your max heart rate by each zone's percentage range. Zones 1 through 5 for a typical 30-year-old would look something like this:
- Zone 1: 95 to 114 BPM (50 to 60% of 190)
- Zone 2: 114 to 133 BPM (60 to 70% of 190)
- Zone 3: 133 to 152 BPM (70 to 80% of 190)
- Zone 4: 152 to 171 BPM (80 to 90% of 190)
- Zone 5: 171 to 190 BPM (90 to 100% of 190)
This method is great for beginners. But for serial athletes or endurance runners whose resting heart rate may be in the 30s and 40s compared to the normal range of 60 to 100 BPM, the Karvonen method would be more accurate, according to Samale. In general, a lower resting heart rate typically indicates better cardiovascular health, according to the American Heart Association.
To calculate your target heart rate zones using the Karvonen Formula, you'll need to find your heart rate reserve. Here's how:
- 220 – your age = max heart rate
- Max heart rate – resting heart rate = heart rate reserve
- Heart rate reserve x minimum zone intensity + resting heart rate = minimum target heart rate for that zone
- Heart rate reserve x maximum zone intensity + resting heart rate = maximum target heart rate for that zone
If you don't have a smartwatch or heart monitor, here's how to calculate your resting heart rate:
- Feel your pulse on the inside of your wrist or on your neck
- Using two fingers, press lightly over the artery
- Count your pulse for 30 seconds and multiply by 2 to find your beats per minute
It's best to do this when you first wake up in the morning, before any coffee, activities or medication that may raise or lower your heart rate, says Samale.
For a 30-year-old with a resting heart rate of 45, here's how their zone 1 heart rate will differ from the simpler age-based formula:
- 220 – 30 = 190
- 190 – 45 = 145
- 145 x 0.5 (Zone 1 min) + 45 = 118
- 145 x 0.6 (Zone 1 max) + 45 = 132
This person's zone 1 target heart rate will be between 118 and 132 BPM, which is closer to the traditional formula's zone 2 range — a pretty significant difference.
Don't want to do the math? Try this Karvonen heart rate calculator to find your target heart rate zones.
"Whichever method you choose, tracking your heart rate over time can give you measurable feedback to see how you're progressing cardiovascularly," says Samale.
How do I know what heart rate zone I'm in?
Rather than calculating your heart rate zones and checking your pulse throughout a workout, Samale says it's often easier to go by the "talk test" — a simple way to roughly measure exercise intensity.
For moderate intensity activity — around zones 2 and 3 — you'll be able to talk but likely won't be able to sing like you would in zone 1, according to Samale. For zones 4 and 5 — or what some people refer to as "vigorous" activity — you won't be able to say more than a few words without having to take a breath.
"Some people prefer the formula-based method, which is great, but for me personally as a trainer, I encourage people to listen to their bodies and go off what they're feeling, especially if they're new to fitness, don't have a heart rate monitor or don't know their zones," says Samale. "The more people can be in tune with their body, the more confident and empowered they're going to be in their fitness journey."
What's the best heart rate zone to be in?
"The 'best' heart rate zone is really going to depend on the person and their health and fitness goals," says Samale. "If we're talking about someone who is new to fitness and is just looking to improve their cardio, I might recommend the majority if not all of their initial cardio to be in zone 2. This is going to help condition their heart a little bit more and build their aerobic base all while still being very gentle on the body."
"For athletes, it's great to work zone 4 where you're doing bursts of power to increase your speed and working those fast-twitch muscle fibers," she adds. "However, if I had to tell everybody to work one intensity, I'd say zone 2 because there are just so many benefits to this zone. Everyone regardless of fitness level should be incorporate more zone 2 into their weekly fitness routine."
According to Samale, a few benefits of incorporating more zone 2 cardio into your fitness routine include:
- Enhanced fat burning: Zone 2 trains your body to be more efficient at using fat for fuel instead of the glucose (sugar) in your muscles and protein.
- Improved mitochondrial function: Zone 2 cardio is the optimal intensity to increase the number and efficiency of mitochondria, the so-called "powerhouses" that are responsible for generating the energy necessary to power our cells.
- Reduced stress and exercise fatigue: Because zone 2 is relatively gentle, your body is going to recover more quickly and experience less fatigue than higher-intensity workouts that can leave you depleted and sore.
- Improved heart health: Zone 2 helps build your aerobic base, which is how efficient your body is in using oxygen to sustain prolonged effort.
- Improved mental wellbeing: Physical activity has been shown to reduce symptoms of anxiety and the risk of developing depression.
Does heart rate zones matter for strength training?
"So yes and no," says Samale. "In a strength training session, you want the limiting factor to be your muscles, not your heart rate, because what you don't want to happen is you go hit the weights, and you're breathing so hard that you can't actually lift as heavy as you should."
That's not to say your heart rate shouldn't go up during strength training sessions, she adds. For example, bigger muscle groups like your quads and hamstrings require lots of oxygen and blood flow, so it's normal during those sessions that your heart rate is going to go up to zone 3 or maybe even higher, depending on the intensity you're going for, Samale says.
However, during weightlifting sessions, if your heart rate is steadily in zone 3 and 4, Samale recommends decreasing the weight and intensity and focus on building your aerobic base through more zone 2 cardio.
"By building up your aerobic base, your heart can work more efficiently in your strength workouts because you want to be challenged by the amount your lifting, not from gasping the whole time," she adds.
(Related: 27 Effective Bodyweight Exercises to Add to Your Workout Routine)
What are some examples of zone 2 exercises?
Cardio is anything that gets your heart pumping faster. Therefore, zone 2 cardio includes any activity that gets your body moving within that moderate-intensity range. Examples include:
- Walking briskly (faster than 2.5 miles per hour)
- Slow jogging
- Swimming at a relaxed pace
- Doubles tennis
- Relaxed biking on flat terrain
- Active forms of yoga
- Dancing
- Yard work
"The important thing is doing something you enjoy," says Samale. "Working out does not have to be miserable, and you don't have to feel completely depleted after a workout for it to count towards your health. In fact, you want to feel more energized after these activities, and if you're doing zone 2, you should feel great and energized afterwards."
