Understanding Cardio Heart Rate Zones (+how to implement now)
Cardio is a hot topic - everyone wants to know what kind of cardio (if any) will help them reach their goals most efficiently. The short answer: moving in any capacity is generally healthy and there is no objectively best cardio (sorry).
Cardio isn’t key to fat loss or muscle gain, but it’s healthy and should play a role in everyones program in some capacity (running alone isn’t going to make you lose weight, it’s also not going to kill your strength gains).
Each cardio zone has its own list of benefits and drawbacks. Understand the basics so you can program intelligently and look past all of the misleading marketing surrounding cardio training (yes I mean bootcamp classes oversimplifying what will help you “lose fat” to sell their service, or app services like ClassPass that tell you that infinite variety in workouts —> progress).
Turns out, as with everything health and fitness, it’s not that complex.. There’s no one magic target heat rate zone that will give you the results you want fast (despite what a lot of group fitness organizations like Orange Theroy, Barry’s, etc would like you to believe).
It’s about being consistent and well-rounded in your training. It’s also about experimenting and finding what you like so you keep doing it, even if that is an over-marketed bootcamp class (consistent movement = happy healthy heart).
Article TOC (for those of you not wanting to read ALL of my lengthy cardio post)
Part I: Defining cardio zones
Part II: How to find YOUR personal target heart rate for each
Part III: Benefits and Drawbacks of each zone (yes, no zone is perfect and ideal for everything)
Part IV: Structuring a simple, effective training program for yourself
Part V: Practical application - an example 5 day training breakdown
Part 1: Cardio zones 1, 2, and 3 defined.
Cardio zone graphics can be useful for a quick reference, but labeling “fat burning” zones is really misleading. If fat loss is the concern, your net calorie intake is what’s important - not the HR zone you’re training in.
Zone 1: You’re working, but it’s easy to talk. You feel like you could continue at this training intensity for a long time. This is the zone you’re usually in during non exercise activity.
Technically, this is any work performed up to Ventilatory Threshhold I (VT1). This is the point up to which your body is the most efficient at utilizing AEROBIC metabolism. Conversation should be easy until VT1. When talking becomes uncomfortable (but still possible) you have reached the threshold at which you are no longer relying primarily on aerobic metabolism.
Zone 2: “Moderate intensity” Talking is possible, but not super comfortable! Starts around ~65% max HR, but varies based on how well trained you are. This should not feel super intense!
Zone 2 begins when you reach that first threshold and ends when you hit the second threshold, or VT2. When you’re able to say just a couple of words in a row, you’ll know you’ve reached this second threshold and are no longer in Zone 2.
Your goal during Zone 2 training is usually to stay working at a steady pace just below that threshold where you can’t talk comfortably anymore. Ideally zone 2 work is done in a minimum of 30 min increments.
Zone 3 - high intensity training up to your body’s maximal oxygen uptake capacity. You should not be able to talk at this intensity. Usually >90% max.
High intensity training performed above VT2 all the way up to your Vo2 max (your body’s maximal oxygen uptake capacity). During Zone 3 training, you’re relying primarily on energy stored in muscles (not energy your body is producing during the effort). Mentally, it’s hard to actually push yourself to this zone. True Zone 3 exercise is taxing and can’t be sustained for long. It should be followed by an interval in Zone I for recovery (that’s where we get the idea behind HIIT, or high intensity interval training).
Part II: Determining your target heart rate for each zone.
Find your target for each zone using the talk test. Most will find their moderate zone and max zone targets to be most useful in training. Vigorous (but not maximal) work is good, but perhaps the least essential for most people - you’re not yet pushing to max oxygen uptake, but you're also not training aerobically anymore.
The talk test is surprisingly accurate and easy to implement.
Start with this protocol: Grab a friend to talk to! Then, begin at a level of work you feel you could do indefinitely. On a treadmill, increase intensity of aerobic work incrementally by adding a percentage of grade (incline) every 2 minutes until talking is labored. Note your heart rate here Increase again until you can only get a couple words out in a row, note HR again. VO2 max (your actual max o2 output) can only be measured in a lab setting, so no use there! To get benefit from zone 3 training you should just be really pushing yourself.
Part III: benefits and drawbacks of each zone.
Zone 1 - Usually below 55% max HR
The good:
Useful during programmed cardio as a tool for recovery periods and warm-ups.
Activates enzymes that convert fat to energy (moving consistently reminds your body how to use fat to fuel activity!)
Moving in any form burns extra calories throughout the day and can add up quickly. Think, 200 calories from walking 2 miles every day —-> 1,400 calories extra deficit a week just from walking a bit extra! 1 lb of fat loss is loosely equivalent to 3,500 calories so that’s significant!
The bad:
This is usually classified as non exercise energy - you are using energy but your cardiovascular system is not reaping all of the benefits we see in the two higher intensity zones!
Zone 2 - Usually about 55-70% max HR
The good:
Undervalued intensity that leads to the important physiological adaptations (aerobic metabolism, stamina, fat burning capacity, energy production, the list goes on)
Less risk of injury for beginners than higher intensity training.
Safe to perform more frequently as it isn’t very stressful on our bodies (joints, adrenals, etc)
Train your body to use oxygen and produce energy (ATP) more efficiently - this will translate to better performance across all training zones (yes, running slowly often —> running faster when it matters!)
Trains our endurance muscle fibers (slow twitch/type I). Translation to strength performance: type I muscle fibers are also important during strength training, especially at high - moderate rep ranges!
The overall density of mitochondria in muscle tissue increases in response to aerobic workouts. More mitochondria means greater use of oxygen to produce more ATP and energy. Too science-y? TOO BAD
Burns more calories during the workout due to duration (but less post exercise calorie consumption than HIIT, so this evens out and isn’t a good reason to choose either training zone).
The bad:
Time consuming/monotonous for some people.
Some additional benefits seen in zone three that you’d miss if 100% of your training is zone 2 (see below)
Zone 3 or HIIT - efforts at more than about 80% max HR
The good:
Time efficient (effective HIIT cardio workouts should be only 10-30 mins long)
Increased stroke volume (amount of blood pumped per heart beat)
Trains our power muscle fiber (fast twitch/type II). Translation to strength: Type II fibers are important in strength training, especially in lower rep/heavy weight sets.
Increased maximum o2 uptake
Increased capacity to store energy (ATP) in muscles for immediate use (muscle glycogen stores!)
Improved recovery time during rest (this means your body gets better at delivering o2 efficiently to fatigued muscles)
The bad
Unclear what the best implementation is (despite many strong opinions from non experts.)
NOT good for beginners - build baseline stength witht steady state moderate work to avoid injury first. Don’t worry, the physiological adaptations we make during lower intensity work are what allows us to then excel at HIIT later!
Burns less calories during as it’s shorter but more post exercise consumption (but again, dumb reason to choose either)
Taxing on muscles - requires significant recovery time between sessions (if you want to see the benefits that is).
Hard to truly push yourself to this level when you’re alone (get comfortable being uncomfortable!)
Part IV: Structuring a simple, effective HR zone cardio program
Use the power output you develop in Zone 3 training to execute cool stunts!
Talk test - use this test to asses what your target heart rate range should be for each zone. Reassess whenever you feel like the target hear rate you’ve determined is no longer accurately reflecting your effort (likely more frequently if you’re a beginner).
Start training in zones 1 and 2. Depending on your goals, you can feel free to include zone 2 training as much as 4-6x per week. This might look like five 30 min sessions at a moderate, continuous pace - this simple plan would get you to the 150 min/wk government recommendation for heart health!
Consider incorporating zone 3: Aim to run or perform your cardio sport for 30 mins contiinuously in zone 2 before incorporating HIIT.
Incorporate HIIT when you’re physically ready. Try 3 mins HARD work, 3-4 mins active recovery.
Multi HR zone training. When you’re ready, replace 1-3 cardio sessions/wk with HIIT training and start to experience the additional benefits discussed above! The majority of your work should not be HIIT, adaptations made during Zone 2 have significant impact on cardio (and strength) performance.
Schedule intelligently - alternate between zone 2 and 3 training days. HIIT is like a heavy strength workout - you need to give a muscle group a good amount of time (48-72 hours) to recover before the next time you work it!
Rest - no matter your program, make sure to take one complete rest day from any and all muscle stimulus (that means even an easy workout!)
Part V: 5-day training split - week breakdown (example)
Training indefinitely in just one cardio zone is like training just one muscle group in strength training. All of our energy production systems work together. To see the best results, an intermediate-advanced athlete should develop a program that targets all zones in some capacity.
Monday: 30 min endurance, zone 2
Tuesday: HIIT
Wednesday: Rest
Thursday: 30 min endurance, zone 2
Friday: HIIT
Saturday: 30-40 min endurance, zone 2
Sunday: Rest
Reference Articles
https://www.acefitness.org/certifiednewsarticle/888/ace-sponsored-research-validating-the-talk-test-as
https://www.issaonline.com/blog/index.cfm/2018/mitochondrial-adaptations-to-aerobic-training
https://www.trainingpeaks.com/blog/zone-2-training-for-endurance-athletes/
https://www.unm.edu/~lkravitz/Article%20folder/talktest.html
https://www.heromovement.net/blog/zone2-training/
https://www.livestrong.com/slideshow/1010147-5-common-myths-highintensity-interval-training-hiit/
https://www.acefitness.org/education-and-resources/lifestyle/blog/6852/6-things-to-know-about-non-exercise-activity-thermogenesis