Are you tired of getting conflicting advice about cardio intensity? One day everyone’s telling you to go all-out with high-intensity training, the next day they’re demonizing anything harder than a leisurely walk.
Here’s the truth: most people are training in the wrong zones entirely. You’re probably not going easy enough when you should be going easy, and you’re probably not going hard enough when you should be going hard.
Instead, you’re likely stuck in that dreaded middle zone – what we call the “gray zone” – where you’re working too hard to build an aerobic base but not hard enough to get the benefits of high-intensity training.
Today, I’m going to break down the zone training system that will revolutionize how you approach cardio, whether you’re a runner, CrossFit athlete, or someone who just wants to get the most out of their gym time.
Training zones are classifications for heart rate and intensity based on physiological markers like heart rate, RPE (rate of perceived exertion), and talk test. Every workout has an intention, and intensity is part of that intention.
Some workouts are meant to be easy efforts, some are meant to be harder efforts. When you understand zones, you can program your training so it actually makes sense – you’re not going all-out all the time, but you’re also not only going easy and neglecting those higher intensities.
Zones aren’t just for runners. You can apply zone training to:
Zone 1 is what most people associate with walking and general daily activity. For most people, this isn’t really a specific intentional exercise zone – it’s just your everyday movement.
Key characteristics:
How to calculate: Your max heart rate is roughly 220 minus your age (give or take 10 beats per minute). So if you’re 30 years old, your estimated max heart rate is 190. Zone 1 would be about 95-115 beats per minute.
Pro tip: You don’t need to turn on your heart rate monitor when walking around the grocery store to make sure you stay in Zone 1.
Zone 2 is the best-kept secret of the cardiovascular training world. This is where the magic happens for building your aerobic base.
Why Zone 2 is so powerful:
The Zone 2 paradox: It often feels too easy, and that’s exactly the point. Zone 2 is intentional training that allows you to accumulate high volume without excessive fatigue.
How to know you’re in Zone 2:
The biggest Zone 2 mistake: Most people can’t stay in Zone 2 because they go too hard. If you find yourself breathing heavier, unable to talk, or feeling unsustainable pace, you’re probably pushing into Zone 3.
Why it’s perfect for hybrid athletes: Zone 2 training isn’t highly fatiguing, so you can do cardiovascular training alongside resistance training without compromising your strength sessions or recovery.
Zone 3 gets a bad rap because it’s known as the “Gray Zone” – and for good reason. This is where most people accidentally spend their training time, and it’s not ideal.
What’s happening in Zone 3:
Why we want to avoid spending too much time here:
When Zone 3 is useful: Threshold runs, tempo runs, some CrossFit metcons. It’s not bad – we just don’t want it to be the bulk of our training.
The biggest culprit: Most people end up running in Zone 3 when they’re actually supposed to be in Zone 2.
Zones 4 and 5 are your higher, harder, maximal intensities. The duration of the activity determines which zone you’re in:
Zone 4 (80-90% Max Heart Rate):
Zone 5 (90-100% Max Heart Rate):
Benefits of Zone 4-5 training:
The key: These zones are highly fatiguing, so you get maximum stimulus with minimal volume. You don’t need as much, but you get robust training adaptations.
The most effective approach to zone training follows what’s called polarized training:
What this looks like practically:
Most people train in Zone 3 all the time – too hard to be easy, too easy to be hard. This leads to chronic fatigue without the benefits of either easy or hard training.
Zone 2 can feel “too easy” and people worry they’re not working hard enough. Remember: easy days should feel easy. That’s how you build your aerobic base.
When it’s time for high-intensity work, many people don’t push hard enough to get into true Zone 4-5. If you’re going to go hard, commit to it.
Heart rate can be affected by:
Learn to use RPE (rate of perceived exertion) and talk test as backup indicators.
If you’re doing cardio for general health a few times per week, it doesn’t really matter if you spend time in Zone 3. Zone 3 isn’t bad – it’s just not optimal for specific training goals.
Follow the 80/20 rule strictly. Build a massive aerobic base with Zone 2, then add specific high-intensity work as you approach your race.
Your metcons probably fall into Zone 3-4. Make sure you’re also complementing this with aerobic training and not just doing high-intensity all the time.
Zone 2 training is your friend. It’s not going to interfere with your strength gains and will improve your work capacity and recovery between sets.
Start with the basic formula (220 – age) but pay attention to how you feel. Your actual max heart rate might be higher or lower than this estimate.
This is the hardest zone to master because it requires patience. Start with run-walk protocols if needed. It takes months to adapt, not weeks.
Start with one high-intensity session per week. Focus on true high-intensity efforts with proper recovery.
Use heart rate as a guide, but also pay attention to:
A lot of what gets labeled as “HIIT” on social media isn’t really high-intensity interval training. Many people are just working in that moderate Zone 3 intensity because:
True HIIT characteristics:
Here’s what I see constantly: people think they need more high-intensity work when they actually need more easy, aerobic base building.
Benefits of more Zone 2 training:
For my lifting friends: Zone 2 cardio is probably not going to be as fatiguing as high-intensity stuff. Don’t be afraid to slowly increase this over time – once you adapt, it’s really not that taxing on your body.
Your heart rate can be affected by:
This is why it’s important to use multiple indicators (heart rate + RPE + talk test) rather than relying solely on your watch.
If you’re a runner looking for programs that implement proper zone training without the guesswork, The Lyss Method has exactly what you need:
Available Programs:
All programs use the zone training principles I’ve outlined here, taking the guesswork out of when to go easy and when to go hard.
Here’s what you need to remember:
The most important takeaway: Stop training in the middle all the time. Go easy when it’s supposed to be easy, and go hard when it’s supposed to be hard. Your cardiovascular fitness will thank you.
Whether you’re a runner training for your first 5K or an experienced athlete looking to optimize your training, understanding and implementing zone training will transform your results.
Ready to stop guessing and start training with purpose? Check out The Lyss Method for programs that implement these zone training principles perfectly for runners of all levels.
Keywords: cardio training zones, heart rate zones, zone 2 training, high intensity interval training, running zones, cardiovascular training, aerobic base training
I’m Exercise Physiologist, sports nutritionist, weight lifter, and ultra runner. I am here to bring science to your training in a no-nonsense way. I have helped thousands of women crush big lifting goals, cross race finish lines, and even do both. I’m here to help you do the same!
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