Heart-rate training is a hot topic among endurance athletes. And I believe for good reason, it’s a great way to stop focusing on pace and start focusing on how your body is reacting to the workout. Zone 4 heart rate training doesn’t get discussed very often, so we’re going to dive in to it today to help you better understand the when and why of using it.
You’ve likely seen the HR metric on your smartwatch or fitness tracker, and maybe you even know that you should be using this metric as part of your training plan.
But do you really know what heart rate training zones are? Are heart rate zones actually important? And why is zone 4 heart rate so important?
Understanding and knowing how to train in your heart rate zones is a great way to improve your performance. If you’re aiming to increase your speed or going for a PR, you’re going to want to understand how to use this metric to your advantage.
Before we can talk about zone 4 and how to train in the threshold zone, you’ll need to understand the different heart rate zones and how they affect your workouts. Since I’ve talked about this in depth before, just a quick primer and then on to Zone 4 HR Training.
What Are Heart Rate zones?
Heart rate zones measure exercise intensity by how hard your heart is working during your workout. Your heart rate can be used as one piece of the puzzle that makes up your overall fitness level.
Your heart rate varies depending on what you’re doing, with your resting heart rate representing the number of beats per minute when you are—you guessed it, resting—to your max heart rate, which is the highest number of beats per minute (bpm) your heart can handle.
The American Heart Association indicates that for adults, the average resting heart rate should be between 60 and 100 beats per minute, but this can vary based on age, overall health, and other factors like stress or certain medications.
In between your resting HR and HR max are 5 zones, and they each represent a percentage range of your maximum heart rate (MHR). Higher zones represent higher intensities and lower zones represent lower intensities. You can think of Zone 1 as the “easy zone” and Zone 5 as your “all out.”
Here’s a breakdown of each HR zone:
It’s important to know there area a variety of formulas for calculating zones, but this gives you an idea.
- Zone 1 (50-60% of MHR): This is your easy zone. It should feel mostly effortless, and should be used for warm-ups, cool-downs, or recovery runs. Zone 1 can help lower your heart rate and prepare you for more intense exercise.
- Zone 2: (60-72% of MHR): Zone 2 is where 80% of your training runs should fall. You should be able to easily carry on a conversation and not feel too much fatigue after a run in this zone.
- Zone 3: (73-83% of MHR): Newer runners sometimes struggle to keep their “easy” runs actually easy, and end up running in Zone 3 instead. Zone 3 should be used for tempo runs. Conversations should more difficult and limited to a few words at a time. This is where you can practice your marathon goal pace.
- Zone 4: (84-93% of MHR): Zone 4 is where you increase your anaerobic tolerance and learn to run at your lactate threshold. This is your hard effort, where your body is relying on carbohydrates for energy. This is where you push your limits and increase your aerobic capacity and VO2 max (peak oxygen intake).
- Zone 5: (94-100% of MHR): Finally, Zone 5 is your all-out, where you’re pushing to your max heart rate. Save this zone for sprints or the very end of a race—that last final push.
Get a more detailed look at how to use HR Zones for training >>
There are many ways to calculate HR zones unfortunately. However, I prefer the Karvonen method.
This uses resting HR and maximum HR to calculate your target zones.
What Happens To Your Body During Zone 4 Training?
Zone 4 is often referred to as the threshold running zone or lactate threshold. This is your high intensity workouts where you’ll improve your speed and endurance.
Zone 4 is where your body is using more carbs (rather than fats) for fuel because carbs are more quickly converted to energy. Your body also gets used to clearing out lactic acid, which means you can maintain a higher intensity workout for longer periods of time.
This graph is a good way of visualizing, how your body always uses both carbs and fats, but as the intensity increases, you see the blue portion of carb usage increase.
This is where you’ll find yourself breathing faster and deeper as your body tries to get more oxygen to your muscles and rid carbon dioxide more quickly. You’re engaging more muscle fibers (particularly the fast-twitch muscles) which are needed for quick, explosive movements.
Ever experienced a “runner’s high“?
You can thank zone 4 for that (or a super long run). Your body is releasing endorphins during this zone, which is what gives you that euphoric feeling we call a runner’s high.
What Are The Benefits of Zone 4 Training?
What’s all the hype about Zone 4 training?
Zone 4 training is important because it’s where you will realize your speed gains, particularly important if you are looking to set a Personal Best in your next race. This is going to apply to all distances from the 1 mile race to the marathon, we need these hard bursts of intensity in training.
Boosts Anaerobic Fitness
Your anaerobic threshold gets a big boost in this zone. This is the point where your body starts to use more glycogen for energy instead of oxygen and fat. Training here improves your ability to handle a high-intensity pace for longer.
Improved Oxygen Consumption
Your body gets better at consuming oxygen, which can enhance your overall athletic performance. Your muscles require oxygen to perform, so the better your body gets at utilizing oxygen from your blood, the longer you can go at harder intensities.
In fact, a 2019 study of threshold based training in triathletes showed significant increases in relative VO2 max after 8 weeks of threshold training.
Improves Your Lactic Acid Clearing
Your muscles will start to feel the burn in Zone 4 running, which means it actually helps to teach your body how to better clear that lactic acid.
Beyond that it actually helps you mentally learn how to train for that end of race discomfort. You’ll understand what it feels like and know that even when your body might be telling you to stop, you can keep going and it’s going to be ok.
By pushing your pace for short periods of time, you’re training your body to be faster. This is important if you’re looking to improve your speed, particularly for race day performance as it also teaches you how different intensities are going to feel.
Even though it’s intense, zone 4 training also helps build endurance. Your body becomes more efficient at clearing out lactic acid, which can delay fatigue and improve your ability to maintain that strong pace.
Enhanced Cardiovascular Strength
Your heart is a muscle, and working it out at this intensity makes it stronger. A stronger heart can pump more blood with each beat, which is good for your overall fitness.
Burns More Calories After the Workout
When you workout in zone 4 your body will continue to burn calories even after your workout. This is known as the afterburn effect, or excess post-exercise oxygen consumption (EPOC).
Does Zone 4 Heart Rate Burn Fat?
Yes. But technically the primary fuel source in Zone 4 is going to be carbohydrates.
What people are referring to when calling this a weight loss workout zone is the afterburn or the high number of calories you burn during the workout.
Again, don’t get too caught up on this post workout burn. We still know that your total volume of calories burned makes a bigger difference if losing body fat is your goal. Which means you need easy days too, not just go short and hard days.
Zone 4 Workout Examples
80% of your training runs should be done in a low heart rate zone (Zone 2 training). But you can incorporate a smaller percentage of your training at the threshold zone in order to start improving your speed and performance.
How do you train in heart rate zone 4? This can be done a few different ways and should absolutely be slowly built in to your program, so that you aren’t over doing it.
Remember that more is not better. We need a variety of workouts in training for different stimulus.
#1 Tempo Runs
Right on the edge of being in Zone 3 and then dipping in to Zone 4 by the end of the workout is a tempo run. I would generally focus these more around threshold training and only be in Zone 4 for a small part of the workout.
Tempo run is a short, sustained effort just above our anaerobic threshold when our body goes from having sufficient oxygen during the run to no longing having it to power our muscles. And that sweet spot, right in the middle, is where all the magic happens.
Learn more about how to do tempo run workouts >>
There is a steady build up process, not just diving in to 30 minutes at that pace.
#2 Hill Repeat Workouts
Ah, hill workouts. Every runner’s dream, right?
Hill workouts are a stellar way to hit the zone 4 exertion level, plus you’ll build leg strength and be more prepared for those hilly race courses. Hill repeats are one of the few well studied workouts that have proven speed benefits, so get ready to rock and roll!!
Find out how to do hill sprint workouts for maximum benefits >>
Again, we have a process. Don’t start day 1 with 10 reps of 60 seconds, we’re actually aiming for shorter and more intense.
If you don’t have any hilly routes nearby, this is the perfect time to get friendly with the treadmill.
#3 800m or Kilometer repeats
One great interval workout to get your HR up is doing 800m repeats at 10K pace (or slightly faster). Again this will shift based on your fitness level and how your HR responds.
The first time you do this workout, you might start with 3 reps with 3 minute jog recovery.
As you get used to finding your effort level and continue to progress through the weeks, you may move all the way up to 8 reps with 90 seconds easy jog between repeats.
This workout is really going to help you work on pacing and finding the right effort that you can sustain for the full workout.
How Long Should You Stay in Zone 4 Heart Rate?
When doing an interval training session, you might stay in zone 4 for short periods, like 2-5 minutes, followed by an equal or slightly longer recovery period.
If you’re doing a tempo run, you might stay in Zone 4 for a longer duration, like 20-30 minutes.
As your fitness improves, you will likely be able to handle longer intervals or durations in Zone 4. The cap is usually going to be an hour before we start to see diminishing returns.
Remember harder is not better, the workout has a specific goal and you need to be able to recover from it quick enough to do your next training session.
Is Zone 3 or Zone 4 Better?
Neither is better, they have different purposes in your training.
The key thing for endurance athletes is that you’re spending the majority of your mileage in Zone 2 doing easy workouts. Then you’ll spread out that other 20% across your total training volume for the week to get different results.
How Often Should You Train in Zone 4?
If you’re new to this level of intensity, start with just one zone 4 session every couple of weeks. Assuming you are doing 4-5 days of running, you need to make sure that you recover well between workouts and understand exactly how your body is responding.
Remember that your training will also shift over the months of preparing for a race.
So it’s unlikely you’ll do much Zone 4 running early in half marathon training, but will increase that load as you get in to more race specific workouts.
If you have a solid base of fitness you might be able to handle one zone 4 workout per week right away, but sure these workouts are separated by at least one or two easier days. Rarely would I put two Zone 4 workouts in one training week because we have so many other modalities of training for endurance athletes.
If you’re unsure where to start, working with a running coach is always a good idea. We can help you come up with a specific training plan to meet your needs.
Want more info?
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