Some people think the sign of a good workout is soreness. After all, if you're not hurting, you're not burning! Others cite the satisfactory feeling of giving it their all, leaving nothing on the field. They can't wait to get home and collapse in their bed after such an intense cycling session!
But what if it's actually none of that? According to Taylor Samale, a senior health fitness coordinator at Houston Methodist, you don't have to go all out all of the time, become completely out of breath or experience significant muscle soreness for your workouts to be successful.
In fact, most of your workouts should leave you feeling like you have more energy than when you started. The trick, per Samale, is to focus on heart rate zone 2 training — a steady-state aerobic workout that's typically performed at a moderate level of intensity. In zone 2, you can still speak in full sentences, but you might be a little breathy.
"If I had to tell everyone to work one intensity in their cardio, I'd say zone 2," says Samale. "You're still getting all of the health benefits of physical activity without the fatigue and soreness that comes with long bouts of high-intensity training. There are lots of benefits to elevating your heart rate a little bit instead of to your max."
Just how beneficial is zone 2? Samale explains why zone 2 might just be the best cardio intensity and the exercises you can do to incorporate more of it into your exercise regime.
What exactly is zone 2 cardio?
When it comes to cardio, think of your heart rate as a measure of intensity. The more intense your physical activity, the more your heart rate is going to increase and the more fat your body burns as fuel. However, beyond a certain level of effort, your body needs more energy than it can burn from fat alone. It then turns, first, to carbohydrates for fuel and, eventually, to protein.
Heart rate zones help to classify cardio activity into five different levels based on intensity and energy source. Zone 1 is the least intense — just above your resting heart rate — and the most intense is zone 5, which is at or near you maximum heart rate and can only be held for a very short amount of time.
Zone 2 is sort of like the "Goldilocks" zone — a moderate intensity level of cardio (about 60 to 70 percent of your max heart rate) that's not so easy as walking but not so intense to where you're breathing heavily out of your mouth.
"You're definitely working, and you're feeling heat building up in your body," says Samale. "You might be lightly sweating, but you can still carry on a conversation and talk in full sentences. If you were on the phone with somebody, they might hear you breathing just a bit harder than normal, but no problem talking otherwise."
According to Samale, it's also the zone most optimal for fat-burning. Enter zone 3, and you've gone too far, but stay in zone 2, and that's where you can train your body to use more fat for fuel versus the glucose (carbs) that is stored in your muscles, she says.
Benefits of training in zone 2
Zone 2 training offers significant health and fitness benefits beyond fat-burning, according to Samale. Here are five reasons you may want to start incorporating more zone 2 into your exercise routine.
1. Enhances fat burning
It's no secret that cardio can lead to weight loss, but according to Samale, zone 2 is "really good" at improving your body's ability to burn fat for fuel.
"Zone 2 is a great place to train at to get your body to use up more fat for fuel instead of the glucose in your muscles," she says. "Our body likes to use glucose for energy because it's quick and easy, and that's what it's there for, but we tend to have more fat storage available. It just takes a little more training and time for our body to utilize that."
(Related: 3 Ways to Improve Your Fat-Burning Workout Plan)
2. Reduces exercise fatigue and overtraining
Zone 2 training also helps prevent you from experiencing exercise fatigue. According to Samale, more intense workouts, including a lot of group fitness classes, can deplete the muscles of their glucose energy reserves (glycogen), which is what often causes people to feel run down, tired, sore and — in some cases — sick after their workouts. Their bodies need time to replenish these short-term energy reserves.
After a zone 2 workout, Samale says you can expect little to no recovery time, which allows for more frequent workouts and greater energy levels because of it.
"When you train more in zone 2, you'll have better endurance and won't hit a wall because you're not depleting your glycogen stores through really intense workouts," says Samale. "Your muscles are adapting by increasing fat transport proteins and the enzymes necessary to break down the fat inside the mitochondria in your body."
3. Improves energy levels
Zone 2, according to Samale, has also been shown to improve the efficiency and density of your mitochondria — known as the powerhouses of the cells because they convert food into energy.
"It's not all about keeping your heart rate super high for the duration of your workout," says Samale. "It's actually more beneficial to keep it in this lower, moderate-intensity state because you increase your mitochondria and get more energy all while still being very gentle on the body."
4. Improves heart health
When it comes to exercise, intensity can be measured two ways: absolute and relative. Relative intensity is the level of effort it takes to do an activity and is related to a person's cardiorespiratory fitness level — the ability to exercise for extended periods of time.
Over time, according to Samale, regular zone 2 training makes the cardiorespiratory system — the heart, lungs and blood vessels — stronger and more fit to deliver oxygen and other nutrients to the body's cells. This is why the same exercises seem to get easier over time but actually require the same amount of energy as needed before.
As your heart gets more efficient at pumping blood and doesn't have to work as hard to keep a steady beat, your resting heart rate actually lowers (yes, it can change over time) — a good thing because, as to the American Heart Association emphasizes, the lower your resting heart rate, the better!
5. Improves mental wellbeing
There are also several mental health benefits to zone 2 workouts, says Samale. Ever heard of runner's high? It's the nickname given to the pleasurable feeling during exercise caused by the release of endorphins, aka the "feel good" hormone that helps manage pain, reduce stress and regulate mood.
Exercise in general, though, has many other effects on brain health besides feeling good. Habitual (regular) physical activity has been shown to improve cognition, including academic performance, processing speed and memory; reduce the risk of dementia; and reduce the risk of depression, according to the U.S. Department of Health and Human Services.
(Related: Is Working Out Before Bed Good or Bad for You?)
How to calculate your zone 2 heart rate
Zone 2 is 60 to 70 percent of your maximum heart rate. To find your maximum heart rate, subtract your age from 220. 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 zone 2's percentage ranges (0.6 and 0.7). Zone 2 for a typical 30-year-old would be about: 114 to 133 BPM (60 to 70% 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, another calculation, known as the Karvonen method, would be more accurate, says Samale. It's based on fitness level. Learn more about it our blog about all five heart rate zones.
How do you know if you're in zone 2?
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.
In zone 1, the least intense cardio, you could carry on a full conversation and even sing a song. In zone 2, you'll still be able to talk but shouldn't be able to sing. You might even sound a bit breathy. However, if you're breathing pretty hard and out of your mouth, you're probably in zone 3, and you should consider lowering your intensity if zone 2's your goal. You won't be able to maintain zones 4 and 5 for very long, as they're pulling from a lot of energy sources to keep your body going and won't be able to maintain that level of activity past a minute, if that.
"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."
How much zone 2 cardio should you be doing per week?
"What zones you'll want to train will depend on the person and their goals," says Samale. "If someone is brand new to fitness or looking to return to a previous fitness level, I would definitely recommend them starting with a majority, if not all, of their cardio in zone 2. This is going to help condition their heart, build their aerobic base and set them up for success."
For athletes or those looking to up their current fitness level, Samale says zone 4 is great to train in short bursts, such as sprints, jump squats, lunge jumps or any another high-intensity interval training (HIIT) technique. These are going to demand a lot of from your muscles and will help you tap into the alternative energy sources that you're looking to strengthen, she says. However, Samale still says you'll want to focus approximately 80 percent of your time in zone 2, while the other 20 percent to be in zone 4.
If you're preparing for a race, Samale says more zone 3 might be beneficial to increase your endurance for those "uncomfortable" moments that come with chasing a certain time or distance.
Regardless of which zones you train, the U.S. Department of Health and Human Services recommends most American adults achieve at least 150 minutes (2 hours and 30 minutes) of moderate-intensity cardio or 75 minutes (1 hour and 15 minutes) of vigorous cardio activity per week.
Moderate-intensity activities closely align with zones 2 and 3, while vigorous activities align more closely with zones 4 and 5.
Some examples of moderate-intensity cardio 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
Examples of vigorous activities include:
- Jogging or running
- Swimming laps
- Singles tennis
- Vigorous dancing
- Biking faster than 10 miles per hour
- Jumping rope
- Heavy yard work (digging or shoveling)
- Hiking uphill with a heavy backpack
- HIIT workouts
- Most group exercise classes
If you are like the vast majority of American adults and don't quite meet those guidelines (yet), that's OK! The key is to "start low and go slow" and gradually work your way up to that amount. Just like Samale's mantra for zone 2 training, you don't want to go "all out" then feel completely depleted or worse — injure yourself. If you're pregnant, an older adult or have a chronic condition, you may also consult a health care provider or physical activity specialist on how to best adjust your activity level for your needs and fitness level.
"As a general recommendation, everybody should be incorporating more zone 2 cardio into their weekly fitness routine," says Samale. "I think there is a misconception that every workout needs to feel like you're going all-out in order to make progress, when in fact, it's more beneficial to do about 80 percent of your workouts at a moderate intensity level."
The important thing is to do something you enjoy, Samale says.
"Working out does not have to be miserable," she says. "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, not like you just ran a marathon."
