Learn how heart rate zones works and how to properly train for endurance sports, including polarised training, high intensity intervals and more.
I use Heart rate training personally during my winter training months when I have general focus on fitness and improving my base, once or twice every two weeks. But below we take a look at heart rate training zones more in general and to help improve those amongst us with a focus more on the distance events.
In this article, you’re going to learn everything you need to know about how heart rate zones work, and exactly what happens to your body, muscles and energy systems as you train in these different zones.
But wait? Isn’t this the same stuff that is in every exercise physiology book and endurance training manual on the face of the planet?
While most endurance manuals will certainly teach you about each of the different heart rate zones, the sad fact is that endurance sports instruction is rife with seriously flawed assumptions and myths about how to properly use these zones, leading to lots of frustrated athletes who are chained to their heart rate monitors or who simply throw up their hands in despair and completely train without any quantification at all – leading to the same results year after year.
For example, one myth is that there’s some kind of mysterious, junk mile, “gray zone” in which you should never, ever train. In this chapter, you’ll instead learn why this zone is absolutely crucial to know how to use properly if you’re ever going to actually race.
But in this article, you’ll get the foundation to understand how there is more than one way to find your endurance salvation, and you’ll learn exactly what you need to know to learn in the next chapter how to use both aerobic training and high-intensity intervals to achieve your goals as quickly as possible.
And while we’re discussing myths, we’ll delve into another myth – the idea that each of the different training intensity zones has some magical cross-over period in which you make a smooth and clean transition from one zone to the next, changing up your utilization of fats vs. carbohydrates as you go. If you, God forbid, somehow break the cardinal rule of venturing from one zone into the next, you’re completely screwed. You’re about to discover why this is complete bull, and how your body is a dynamic machine, and not a zone-switching robot.
Ultimately, in this chapter, you’re going to become smarter than 99% of the endurance athlete population when it comes to truly understanding how your body, muscles and energy systems truly operate when you’re swimming, cycling or running.
You’re about to cut through the crap of Zone 1, Zone 2, Zone 3, Zone 4, Zone 5, Zone 6a, Zone 7x, Zone 8abc and every other confusing Zone training alphabet soup that exists.
You’re about to become a clear-thinking exercise physiology ninja.
Oh, one other thing. I’m not big on writing scientific chapters. Instead ill just try get to the point 🙂
Energy Systems 101
The human body gets energy by converting food into something called adenosine triphosphate (ATP), and then breaking ATP into adenosine diphosphate (ADP) and phosphate (P). As you produce energy, you obviously have to replace ATP, and there are three ways that you can do this. These three ways are called energy systems.
Pretty much all heart rate zone training systems are based on these three energy systems.
1. The first energy system is your oxidative system, which predominates for just about anything over 2 minutes. You probably are familiar with this as your “aerobic energy system”, and sometimes it’s referred to as “mitochondrial respiration”.
Basically, when you’re using the aerobic, oxidative energy system, you are utilizing a combination of fats and carbohydrates to resynthesize your ATP, and your body does this by combining glucose or fats with oxygen to form water, carbon dioxide and energy. Once you’ve been out there exercising more than around two to three hours, your body begins to throw protein into the mix as one more fuel that can be broken down into glucose and fed into this energy system.
But there’s no “magic switchover” to fat or carbohydrates or protein as the preferred fuel source for your aerobic energy system. It’s always a mix.
For example, depending on how good you are at using fat as a fuel, what you’ve been eating lately, and which hormones are circulating in your body, at rest about 70% of the ATP you produce is from fats and about 30% from carbohydrates. As you exercise with more intensity, you’ll start to utilize more carbohydrates, but it’s always a bit of a mix. And as you exercise more than 3 hours, up to 18% up your energy can be derived from breakdown of protein.
The graph below (from http://footballsuccess.co.uk) is a great visual example of exercise intensity combined with the concept of mixed fuel utilization:
As you check out the graph above, think of plasma glucose as something you’d get from a gel or sports drink or bar (or from the breakdown of protein); plasma free fatty acids as something you’d get from breaking down your own fat tissue, or from a dietary source of fat; muscle triglycerides as stored fat in muscle (or perhaps from an external source like coconut oil, if that’s your fuel of choice), and muscle glycogen as your body’s storage carbohydrate.
2. The second energy system is your glycolytic energy system, which is often referred to as your anaerobic system.
The glycolytic system, as the name suggests, relies primarily on glycolysis (the breakdown of carbohydrates) from either glycogen stored in your muscles or liver, or glucose delivered in the blood from food. This energy system predominates at intense efforts under 2 minutes during which oxygen is in short supply – but is also something you’ll rely upon quite heavily if you’re in the middle of an Ironman triathlon and trying to pass someone on the bicycle, or you’re on the final kick of a marathon, or you’re surging up to pack of swimmers in the open water. During glycolysis, your body converts carbohydrate sugar into pyruvate, which gets converted into energy (plus some lactic acid).
Interestingly, some of the pyruvate can also get shuttled back into the aerobic, oxidative energy system described earlier, and some of the lactate can get converted back into glucose for use in more glycolysis, once again highlighting the fact that this is a messy system full of cross-overs – and later you’re going to learn how to take advantage of each of those cross-overs so that you can maximize your fuel utilization.
3. The final energy system is the phosphagenic energy system, and exercise at a maximal intensity of three to thirty seconds (depending on which physiology propellor hat professor you ask) uses this system.
When your body creates ATP using the phosphagenic energy system, it breaks adenisone diphosphate (ADP) into adenosine monophosphate (AMP) and inorganic phosphate (Pi), and also combines Pi with another substance called creatine to form creatine phosphate (CP), which can then be combined with ADP to form more ATP.
Most endurance coaches and athletes brush over the phosphagenic energy system as something reserved for football players, sprinters, or a bench pressing competition, but the fact is that the creation of ATP using this energy system is one of the ways that your body can maintain glycolysis during tough efforts or surges in a training session or race.
Traditionally, it has been thought that that 30 second mark was the extreme maximum amount of time you’d actually be able to tap into your creatine phosphate system, but studies have shown that creatine can contribute to ATP production during exercise well beyond 5 minutes and up to nearly 20 minutes of exercise.
How can this be?
The fact that you can use creatine during endurance efforts is simply based on what is called the “size principle” of muscle. The size principle states that when smaller muscles fail to meet power demands, larger muscles are then recruited. This progressive recruitment means that the creatine utilization from larger muscles won’t be tapped into until your reach higher intensities of exercise. So if you’re doing an Ironman triathlon, it’s not as though you tap into your creatine system during the first 10-30 seconds of the swim, and then that energy system is smoked and you’re on to the next energy system.
Instead, while cycling during the bike leg in an Ironman triathlon, you may continue to tap into your larger muscle fiber creatine stores when you surge to pass somebody on the bike, or when you put forth an increase in effort running up a steep hill on the run course.
And the important take-away from this is that an endurance athlete with low creatine stores (e.g. many vegan or vegetarian endurance athletes) or an endurance athlete who has performed zero training of their phosphagenic energy system is setting themselves up to have less “kick”, lower force production, and reduced ability to surge during a race when it really matters – not just when they’re lifting weights at the gym.
Of course, as I’ve already alluded to, contribution of these energy systems to your training and racing is extremely multi-factorial and complex, a fact that Tim Noakes highlighted in a good paper several years ago.
For example, when it comes to dietary status, consumption of a high carbohydrate diet is related to increased carbohydrate utilization during exercise, which means that you would rely upon a greater percentage of carbohydrates as a fuel for your oxidative system described above, and could be using a higher percentage of your glycolytic energy system. In contrast, reliance on carbohydrate decreases and fat oxidation increases during exercise following a low-carbohydrate, high-fat diet (and in some cases, increasing fat availability immediately before exercise can actually increase endurance performance, as well as enhance recovery), and a “fat adapted” athlete may rely more on mitochondrial respiration.
Training status can also influence what kind of fuel your energy systems use. For example, due to higher density of mitochondria and more capillaries feeding into muscle, trained endurance athletes rely less on muscle glycogen and plasma glucose and more on fats as an energy source during any given resting or exercise intensity.
Hormonal status is also an influencer of the type of energy used. For example, high levels of circulating catecholamines such as growth hormone, cortisol, epinephrine and norepinephrine can cause you to burn more carbohydrates as a fuel, but endurance trained athletes tend to produce less of these compounds during exercise.
You get the idea: not only do you use a mix of energy systems for any given intensity, but a big influencer of which energy system you use and which fuel you feed into that energy system is based on your unique diet, training and hormonal status.
Once again, humans are messy.
Why We Invented Training “Zones”
Now don’t worry – we’re getting closer and closer to the practical, hands-on stuff.
So as you now know, we’re going to use a mix of energy systems for any given intensity. So by quantifying and controlling our intensity we can (to a certain extent) control which of these three energy systems is predominating during our training and racing, and we can create intelligent training programs and get valuable feedback from our workouts.
Hence the existence of training “zones” to quantify and control intensity.
Let’s start simple.
As I’m at my standing workstation writing this chapter, I’m in a training zone. A very low one that derives lots of fats and a little bit of carbohydrates as a fuel. But because I’m standing and moving about just a little, I’m technically in a training zone. Or at least it makes me feel good to think that at least a few of those mitochondria are respiring. Despite being chained to a computer, I’m trying to stay in as much a “hunter gatherer” mode as possible (another good reason to get a treadmill workstation).
And when I wander to my office doorway to do few pull-ups and about 30 seconds of explosive jumping jacks (which I do every hour when I’m writing), I’ll be shifting into another zone, one that relies quite a bit upon glucose and creatine phosphate.
Then in my afternoon run later today, I’ll be shifting between slightly higher intensity aerobic mitochondrial respiration as I warm up, then into glycolysis and carbohydrate utilization as I surge into some intervals, then back into an aerobic state as I cool down.
If I wanted to graph this throughout the day, I’d see a shift from Zone 1/2 to Zone 5 to to Zone 3 to Zone 4 and back to Zone 1/2.
If I stayed in Zone 1 all day, I probably wouldn’t get very fit.
And if I stayed in Zone 4 all day, I’d be over trained and get injured.
Simple example, I know – but I really want to make sure this whole physiology thing is clear (after all, I promised I’d turn you into an exercise physiology ninja).
How Many Zones Should You Use?
You’re about to learn five different training zones, but there’s no rule that an endurance athlete has to be married to the magic number of five. Depending on which coach, sport governing body or training system you reference, there are a variety of different intensity zone schemes to choose from.
For example, the Norwegian Olympic Federation has a 5 zone heart rate scale based on decades of testing lactic acid levels in cross-country skiers, biathletes, and rowers, while several other studies (Esteve-Lanao et al., 2005; Seiler and Kjerland, 2006; Zapico et al., 2007, Lucia et al., 1999; Lucia et al., 2003) have relied upon changes in oxygen utilization to instead identify just three training zones. On websites such as TrainingPeaks, the platform I personally use to coach my athletes, you can choose and customize up to 10 different zones – enough zones to make one cross-eyed during training!
In reality, most of these zones overlap and achieve similar effects. For example, a 5-zone scale and a 3-zone scale are relatively super-imposable, since the aerobic, fat-burning intensity defined in Zone 3 of a five-zone system will usually correlate with the aerobic Zone 2 in a three-zone system and the aerobic Zones 4-6 in a ten-zone system.
So for the purposes of this book, you’re going to get intensity and physiology explained to you using five zones in the chart below. After over a decade of working with intensity scales, I’ve found that five zones is enough to allow for some complexity and a good explanation of endurance physiology, but doesn’t get as excessively complex as more zones can be, or excessively simple as fewer zones can be.
I used to use a Zone 6, but now I just call it anything above Zone 5, since I’m not an advocate of looking at your heart rate monitor while you’re doing power cleans at the gym.
Zone Training Chart
|Heart Rate Zone||% of your Lactic Acid Threshold(LT)
|Zone 1 Goals: RecoveryEnergy System: Oxidative||70-76%||After hard workouts or tough blocks of training, very easy workouts can accelerate recovery more than complete rest. Easy aerobic training stimulates blood circulation, which can assist with removal of inflammation and increase your tissue healing response.The intensity in this zone is enough to increase blood circulation and trigger a growth hormone response, but not intense enough to cause any muscle damage, and very little energy and fluid depletion. Examples of a Zone 1 workout would be an easy yoga class, a light swim, a walk with the dog, etc.|
|Zone 2 Goals: EnduranceEnergy System: Oxidative||77-85%||This zone will also feel very easy (“conversational” effort). Training at this intensity primarily uses slow-twitch muscle fibers, since these fibers provide more most of the mobility for events lasting 2 minutes or longer, workouts at this intensity should comprise most of your training.Training above this intensity will not significantly overload your slow-twitch fibers, which you are attempting to train to become more efficient at using fat and oxygen to produce energy while conserving carbohydrate stores. If you don’t have a physically active job or aren’t able to spend lots of time on your feet during the day, this intensity is important for training the body to use fat as a fuel, especially for individuals who compete in events lasting more than two hours.Although it will be difficult to keep your intensity low on these days, if you’ve decided that you have lots of time on your hands and the type of training you want to do is primarily aerobic (vs. interval based training), then performing your endurance efforts at a higher intensity than Zone 2 will reduce the effectiveness of your harder workouts on subsequent days by fatiguing muscle and depleting carbohydrate stores in fast-twitch muscle. This can lead to overtraining and injury. In other words, if you’re going to use the “long, slow aerobic” method of training, you need to do most of it in Zone 2, not Zone 3, which is a huge mistake many endurance athletes make.|
|Zone 3 Goals: Muscular EnduranceEnergy System: Oxidative, Glycolytic||86-95%||During an endurance workout, your intensity may reach this zone on slight hills, or when you’re beginning to push the pace on flats. Your body is still primarily functioning aerobically, conversation is possible, and burning in the legs and shortness of breath is minimal, but you’re still “working”.A slight problem with this zone is that the intensity is too high for maximal stimulation of the slow-twitch muscle fibers and fat-burning. As intensity increases from zone 2 to zone 3, oxygen debt becomes greater, and since it takes more oxygen to burn one calorie from fat than from carbohydrate, more carbohydrate and less fat will be burned. Because this zone is high enough to get the physiological “runner’s high” and the satisfaction that you exercised with a slight amount of intensity, many athletes perform mile after mile in this zone, wear their bodies down, and never get significantly faster.On the flip side, this zone is, as you’ll learn later, the “money” zone for many distances in endurance sports, as it allows you to go relatively fast without dipping too significantly into your carbohydrate stores. This is why long interval training sessions or hill climbs in this zone can really help with race pace training and race preparation.Good for 8-20 minute intervals with short recovery periods between intervals.|
|Zone 4 Goals: Muscular Endurance, Lactic Acid Tolerance, Low-End SpeedEnergy System: Oxidative, Glycolytic||96-103%||Lactate threshold (LT), also called anaerobic threshold (AT), is the highest intensity at which your body can recycle lactic acid as quickly as it is produced. At this intensity, you are working very hard, but can still maintain your maximum sustainable pace and relatively good form because lactic acid levels in the blood and muscles are steady, not increasing.Increasing the intensity above this zone or towards the high end of this zone can cause lactic acid to more rapidly accumulate and bring premature fatigue and delayed recovery due to acidic hydrogen ion build-up and more rapid carbohydrate depletion. Performing interval training sessions near lactate threshold can teach your body to decrease the amount of lactic acid being produced and increase lactate removal at any given intensity.At this intensity, the fast-twitch fibers can be trained to produce less lactic acid and the slow twitch fibers can be trained to burn more lactic acid, both of which raise the lactic acid threshold and allow you to work harder at a higher intensity. Since you’re not at an all-out, high-impact pace as you would be in higher, fast-twitch muscle utilizing zones, recovery from Zone 4 training can occur quicker than recovery from other high-intensity training zones, and from an interval training standpoint, zone 4 training gives you a lot of bang for your buck.When you experience “rubbery leg” syndrome, a marked increase in breathing difficulty, or an inability to maintain good form, you have reached the point where lactic acid is accumulating at a faster rate than it can be removed, which can significantly decrease your ability to maintain a steady effort and also has significant recovery implications.Good for 1 to 7 minute intervals with about a 2:1 to 3:1 work:rest ratios.|
|Zone 5 Goals: Sustained Speed, Leg/Arm TurnoverEnergy System: Glycolytic, Phosphagenic||104-max%||At this zone, your intensity now exceeds your lactate threshold and your body is relatively stressed in its ability to withstand high lactate levels and remove lactate. In Zone 5, lactic acid builds up quickly, so this intensity cannot be sustained for long periods, but is useful for sustained surges of up to around 5 minutes, as there is still some contribution from aerobic energy systems.Because muscle and joint impact and lactic acid levels become extremely high in this zone, this type of training requires longer recovery periods between both workouts and intervals, especially in beginner athletes. In addition to increasing an athlete’s speed, training at this intensity will improve neuromuscular recruitment, economy, efficiency and turnover, but high levels of training in this zone is another common cause of overtraining. Typically, the only work done in this zone is interval training and hill repeats.Good for 2-5 minute intervals with 1:1 to 1:3 work:rest ratios.|
|Anything Above Zone 5: Explosive Speed, PowerEnergy System: Phosphagenic||max||This intensity is primarily training your glycolytic and phosphagenic energy systems, and can involve sets of anywhere from 5 seconds up to a couple minutes in duration. Athletes who want development in their fast-twitch muscles, strength, explosive power, or improvement in cycling or running mechanics should include training sessions at this level.These type of workouts are typified by short, explosive intervals followed by long recoveries, and include powerlifting, weight training, plyometrics and short bursts of energy.|
How To Find Your Personal Zones
Did you notice how the second column in the chart above is based on a percentage of your lactic acid threshold?
The only reason I use a percentage of lactic acid threshold rather than a percentage of your maximum heart rate is because testing your lactic acid threshold is a submaximal protocol that does not require you to run or bike until you collapse (also known as a VO2 max test). It’s just a safer and slightly more pleasant way to keep track of your starting point to develop your zones.
And yes, you can use speed (pace) or power if you’d prefer to track and train with those parameters rather than using heart rate. It’s just that for the purposes of explaining the basic physiology behind these training zones, heart rate offers a great example. If we were going to use pace zones, I’d prefer the Jack Daniels method (no whiskey involved), and if power zones, the Andy Coggan method. There’s also a fascinating and useful method that can even be combined with heart rate, power or pace zones and that is breathing zones – for more on that, check out the book “Running On Air” by Budd Coates.
But for now, let’s focus on heart rate zones, setting your heart rate zones properly, and how to test your personal lactic acid threshold, or your “LT heart rate” so that you have personalized setup of your own heart rate zones.
The gold standard method to determine your LT heart rate is via a lab test, in which blood lactate levels are collected during exercise. But let’s say you don’t want to spend the money or take the time to venture into your local sports performance lab or university to have this test done.
Based on clear signals that occur in your body when you are at or very near LT, you can approximate your personal LT with what is called a “field test”. Due to the varying muscular demands of each skill, your LT will change depending on whether you are cycling or running, so I recommend an LT test on both the bike and run. Based on where your LT lies in each sport, you will be equipped with the knowledge to train at the highest intensity that is possible (without overtraining) and also equipped to determine each of your training zones.
There is no perfect LT field test, but here is an example for running, cycling and swimming. You’ll need a heart rate monitor or somewhat accurate way to count pulse for the running and cycling tests, and preferably some kind of swim pace or timing device like a Finis Tempo Trainer for the swim test:
Running LT Test: The goal of this test is to exercise for 30 minutes at the highest effort that can be sustained and monitor your heart rate throughout the test. Your average heart rate during the final 20 minutes should correspond to your LT.
Sometimes people exercise too hard for this test. Follow this simple rule – your pace should be the same at the end as at the beginning. If the legs begin to go rubbery, the leg turnover begins to slow, the lungs begin to burn, and you begin to gasp for breath, then you are going too hard! This should be about an 8 on a 1-10 scale, if 10 is the hardest and 1 is the easiest.
Warm-up easily for 10-15 minutes, then, on a treadmill, track or flat outdoor course, begin a 30 minute run and work up to your maximum *sustainable* intensity within the first 10 minutes. Record your heart rate for the last 20 minutes. Calculate your average heart rate over the last 20 minutes. This average heart rate figure is your estimated heart rate at your lactate threshold.
If 30 minutes is daunting, this test can be modified by simply performing three 5 minute hard, sustainable efforts with 5 minutes rest between each effort.
Cycling LT Test: Warm-up with 10-15 minutes of light cycling, and then do the same test as described above, but on the bike – preferably on an indoor trainer or controlled course.
An alternative method is, following the warm-up, to cycle for 8 minutes as steady and fast as possible up a slight hill (2-3%), at 80-100RPM. Record your average heart rate during the climb, then rest 3 minutes (or descend). Repeat 1x, and record your LT heart rate for cycling as an average of your two 8 minute climbs.
You now know what energy systems and fuels you’re tapping into at each exercise intensity, and you know how to test yourself to set up your personal zones.
Feeling like an exercise physiology ninja yet?
For those of you chomping at the bit to put your knowledge to the test, there’s just one other carrot I want to throw your way (before we move into the chapter that will teach you how to actually use your zones to train properly). So here’s an example of how to use your zones in a race.
Example Of Using Zones In Training
Once you know your zones, you (or your coach) can use these zones to more strategically build your training program. For example:
-Can you go for a long period of time, but get tired as soon as you begin producing lactic acid? Use more Zone 4 intervals…
-Can you do interval workouts quite well, but fatigue after plodding for long periods of time? Do more Zone 2 efforts combined with quality, focused Zone 3 intervals…
-Do you lack the ability for the final kick in a 5K, marathon, triathlon, etc.? Do more Zone 5 intervals…
-Do you need a recovery day? Do a Zone 1 workout for greater blood flow and faster recovery…
A *fantastic* chart that shows some of the best interval time lengths and recovery time lengths for effective use of zone training is one that I discovered at http://www.sportsci.org:
Example Of Using Zones In Racing
Since it’s a mix of three different sports, triathlon offers a perfect way to give an example of how the training zones can be used in pacing and racing. Here’s how:
Sprint: In a Sprint triathlon, beginner triathletes will bike in Zone 3 to Zone 4, and more advanced athletes will bike in Zone 4 to Zone 5 the entire time. During the Sprint triathlon run, both beginners and advanced triathletes will be mostly in Zone 4 to Zone 5, and advanced triathletes will be primarily in Zone 5 the entire run. Even though it can be tough to quantify swim pace during a short race, swimmers of all levels should try to swim about 5-10 seconds faster than CSS pace for the swim.
Olympic: Olympic distance triathlon is slightly less intense than sprint, and while beginners will again be in primarily Zone 3 to 4 on the bike, more advanced athletes may repeatedly find themselves surging into Zone 5 on the bike. For the run, beginner athletes should stay in primarily Zones 3 to 4 until just 1-2 miles are remaining, at which point, intensity can go up to Zones 4-5. For advanced athletes, the run will start in Zone 4 up to the 5K mark, and gradually build up to Zone 5 from the 5K to the finish. Beginner athletes will be close to CSS during the Olympic swim, while intermediate-advanced athletes will swim about 5-10 seconds faster than CSS pace.
Half-Ironman: In a Half-Ironman for beginner athletes, the bike intensity should primarily be Zone 3, and then the run should be a gradual build from Zone 3 up to the 15K mark, and finish with Zone 4-5 for the final 5K. In a Half-Ironman for more advanced athletes, the bike intensity should primarily be high Zone 3 and low Zone 4, with occasional surges above Zone 4, and on most courses the run should be a gradual build from Zone 3 up to the 10K mark, up to Zone 4 for the next 5K and finishing with Zone 5 for the final 5K. Beginner athletes will be close to or slightly below CSS during the Half-Ironman swim, while intermediate-advanced athletes will swim at or slightly faster than CSS pace.
Ironman: For Ironman, the bike intensity should be primarily low-to-mid Zone 3 for beginner to advanced athletes, although advanced athletes may push towards the high end of Zone 3 on hills or in crosswinds, and when passing may occasionally go into Zone 4. During the Ironman marathon, heart rate and zones can be difficult to rely upon, and pace or perceived exertion becomes a better guide. For beginner athletes, the run should stay near Zone 3 pace all the way up to the 20 mile mark, at which point intensity can build to Zone 4-5 for the final 10K. For advanced athletes, much of the run should also be done near Zone 3 pace, but that same build in intensity to Zone 4-5 may begin as early as the half-marathon mark. Beginner athletes will be 10-15 seconds below CSS during the Ironman swim, while intermediate-advanced athletes will swim at or about 5 seconds below CSS pace.
Like I mentioned, I’m not a fan of writing pure science, and once we finish wading through this physiology stuff, the rest of this book is going to focus on the nitty-gritty, in-the-trenches training instruction, along with cool bio-hacks and everything you need to find the ideal balance between optimizing performance, and still living to see your grandchildren and look sexy as hell as you age.
In reality, most exercise enthusiasts don’t really need a heart rate monitor or training zones to know what constitutes an all-out one-minute interval, an all-out 5-minute interval, or an easy recovery interval. But you now know what you need to know about how heart rate zones work, and even if you don’t use heart rate zones per se, I hope you understand the physiology behind what’s going on as you train and move across a variety of intensities.
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You can best use these Heart Rate training zones when training for your next marathon, using our plan HERE