Released on January 2, 2026, at 04:36 AM Your body is wonderfully distinct. I resemble John Mayer if he were a physical therapist. Our bodie...
Your body is wonderfully distinct. I resemble John Mayer if he were a physical therapist. Our bodies are amazing places, even if our glutes are neglected areas.
The distinctiveness of each athlete presents a challenge. How can we grasp our physiology within the larger framework of training theory when every factor follows a bell curve throughout the population?
Many of you may be familiar with the equation related to heart rate: 180 beats per minute minus age equals roughly the aerobic threshold, which is the intensity level that marks the upper limit for easy or steady running and should make up about 80% of your training. Although this formula is typically helpful, it can be ineffective for certain individuals, particularly older athletes who are well-trained and have a significantly higher aerobic threshold than what the equation suggests.
For me, the equation limits my easy runs to a heart rate of 145. My true aerobic threshold is 152 beats per minute when running (and 150 beats per minute when cycling). In reality, that's nearly a one-minute-per-mile difference in performance. Using a general equation would stop me from gaining advantages from more consistent paces, and I'd likely be slower overall.
Training zones from your watch can also be terrible. Over the past few months, I have assisted a few hundred listeners ofour podcastdetermine their heart rate zones (ourepisode about heart rate zones is available). And a lesson I've learned is that certain watch brands employ algorithms that aren't particularly precise. Some of the watch zones are configured so low that I can't fathom what they might be measuring.
Today, let's explore a straightforward method to determine your heart rate zones, which can assist in adjusting your workout intensity. Understanding your intensity levels is beneficial as it enhances your metabolic fitness, enabling your body to burn more fat at increased exertion levels, while promoting the growth and efficiency of mitochondria, making both high and low intensities less energy-consuming. Here ismy favorite infographic everon the intersection of these principles.
What Are Different Heart Rate Levels?
We will be employing the conventional Five-Zone model, which differs from the Three-Zone model commonly utilized in training studies. However, it is beneficial to grasp both models and their interactions. Heart rate can be considered an indicator of lactate levels. To make it much simpler, lactate is generated when our bodies utilize glucose to produce ATP through glycolysis. Lactate serves as a fuel for cells and is paired with a hydrogen ion that affects muscle pH and leads to fatigue. A2018 review in Cell Metabolismexplained the lactate shuttle, in which cells utilize lactate as a source of energy. If this transport system becomes overloaded, lactate concentrations and tiredness increase, making physical activity harder to maintain. Read thisexcellent summary by Dr. Howard Luks.
As lactate levels start to increase, the intensity shifts from light to moderate, marking an inflection point referred to as LT1, which generally aligns with the aerobic threshold, where athletes transition from mainly utilizing fat to primarily using glycogen. When lactate concentrations rise more rapidly at higher intensities, the effort moves from moderate to strenuous, representing another inflection point known as LT2, which typically corresponds to the traditional lactate threshold (or critical velocity, depending on the calculation method). This forms the basis of the 3-Zone model utilized in research:
- Zone one: below LT1, or approximately 2 mmol of lactate with individual variation (consider very easy running up to more)steady running for advanced athletes)
- Zone two: between LT1 and LT2, typically ranging from about 2 to 4 mmol of lactate (refer to steady running to traditional threshold, or roughly a 1-hour workout or slightly more intense)
- Zone three: above LT2 (consider quicker intervals and more intense hill training)
These areas are utilized in studies to analyze how intensity is spread out. Although these divisions are rough estimates, they can provide some numerical data to help you understand the general situation (all of these figures come with significant margins of error).
- A pyramid model commonly utilized by top athletes typically includes approximately 75-85% in light Zone 1, 10-20% in moderate Zone 2, and 5-10% in intense Zone 3.
- A model with a polarized distribution includes approximately 75-85% in the easy Zone 1, about 5-10% in the moderate Zone 2, and roughly 10-15% in the difficult Zone 3.
- A model of a threshold as some have described“Norwegian” trainingincludes approximately 60-75% in the easy Zone 1, 20-30% in the moderate Zone 2, and a minor portion in the challenging Zone 3
If we are relying on heart rate to estimate lactate levels and the related physical effects of fatigue, then why not directly measure lactate? In an ideal scenario, athletes might choose to perform finger pricks for blood lactate tests after each interval, similar to how Norwegian vampires might do it. However, in reality, there is a learning curve involved with lactate testing, which can result in unreliable data. Moreover, it may also remove some of the natural creativity from everyday training sessions.
By applying the approach outlined in the article, I have estimated zones for professional athletes that have since been confirmed through laboratory testing with error margins small enough to be practical. Nevertheless, it is essential to undergo a complete laboratory test for the most precise results. Measuring heart rate alone, without lactate, metabolic, or ventilatory lab tests, is similar to figuring out the time based on the position of the sun in the sky. With some clues, you might get fairly close.
Five-Zone Training Model
Now, let's finally examine the Five-Zone heart rate model that is commonly utilized in most training methods. The Three-Zone model is represented with green, yellow, and red (once more, there is discussion regarding the precise division, especially concerning the boundary between Zone Three and Zone Four).
- Zone One: mainly focused on ease/recovery/regeneration, burning primarily fat, with minimal lactate accumulation. Athletes can engage in full conversations and sustain activity for extended periods with proper nutrition/hydration and training.
- Zone Two: ranging from easy to steady, limited at the upper end by LT1, where the body starts to generate more lactate and breathing rate rises. The upper limit of Zone 2 can be maintained for several hours, depending on the athlete's level of training.
- Zone Three: medium to somewhat intense, often referred to as pace. Athletes can speak in full sentences, and it usually feels easy, sometimes maintainable for several hours with adequate nutrition.
- Zone Four: moderately intense threshold training. For our context, the upper limit of Zone four is defined by LT2, although certain methods may set it at a lower point. Athletes can speak in short, broken sentences and maintain the highest level of effort for approximately 30-60 minutes, depending on how the zone is established.
- Zone Five: high-intensity intervals, commonly referred to as VO2 max or repetition training. This is a wide category that includes the most demanding intervals and more challenging efforts, and it is sometimes divided into additional sub-zones in certain methods.
There are several methods for setting zones, but I find the Lactate Threshold Heart Rate approach, developed by renowned coach Joe Friel, offers the best consistency and precision.As detailed in Training Peaks, he recommends that athletes "perform a 30-minute time trial alone (without training partners and not during a race). It should be conducted again"as though it were a competition lasting the entire 30 minutesBut after 10 minutes of the test, press the lap button on your heart rate monitor. Once completed, check to see what your average heart rate was over the past 20 minutes.
I prefer athletes to perform tests on inclines, where they won't be restricted by neuromuscular and biomechanical factors if they haven't undergone significant speed training. If the effort isn't genuinely intense or if your heart rate takes a while to rise during the activity, you can use an average heart rate from a segment as brief as 10 minutes. Since this isn't a precise measurement like in a laboratory setting, consider it more of an art that helps you understand your body, rather than seeking a definitive answer like in high school algebra.
For a simple method to clean data files with HR variations, you can utilize theStrava Sauce browser plug-in, highlight the area you wish to analyze, and it will provide averages without ever overlapping the watch. When I calculate zones for athletes, I have discovered that you can also estimate LTHR from nearly any intense workout with intervals of 3 minutes or more by identifying points in the data where heart rate remains steady for 15-30 seconds before increasing to less sustainable levels (and occasionally dropping back toward that baseline in longer efforts). Be cautious when using data from extremely hot days or long races exceeding 90 minutes, as heart rate can sometimes stay above Friel’s LTHR in ways that do not reflect the actual physiological conditions.
A crucial point here is that the data must be precise. Chest straps are best suited for this, and if you're exercising to establish heart rate zones, it's beneficial to use a chest strap. Although wrist straps are becoming more accurate, there is significant variation across athletes and watch brands. For instance, my Garmin 745 performs quite well in most situations (see this beautiful grapha threshold workout). However, other athletes don't experience the same success, and occasionally they send me heart rate files that resemble Bitcoin price charts.
How to Define Your Heart Rate Zones
Once you have your LTHR value, it's time to define those hard-to-pin-down training zones. This is another area of contention, as the specific percentages are heavily debated. The issue is that when you cross-check heart rate data with lab testing, there's significant variation in individual physiology. LTHR helps narrow down these physiological differences to estimate zones, but the exact boundaries depend on factors like training background, muscle fiber composition, metabolic conditions, and even astrological signs. Let's not start a conversation about Scorpios.
Here are the figures I prefer to use:
- Zone one: below 80% of LTHR
- Zone two: 80% to 88% of LTHR
- Zone three: 89% to 94% of maximum heart rate during exercise
- Zone four: 95% to 100% of LTHR
- Zone five: above LTHR
Let's explore an example from my data. In February, I participated in a virtual bike race up a mountain. By using the Strava Sauce plug-in and focusing on the last 20 minutes of that intense effort, my LTHR came out to 172. Although there can be differences across sports and my heart rate tends to be higher when running, this indicates my current heart rate zones for cycling are roughly:
- Zone one: below 137 beats per minute
- Zone two: 137 to 150 beats per minute
- Zone three: 151 to 161 beats per minute
- Zone four: 162 to 172 beats per minute
- Zone five: above 172 beats per minute
Your LTHR can rise with training and decrease as you age. Athletes typically have values between 165 and 175, although in professional athletes, I've observed numbers as high as 189 and as low as 152. This illustrates the importance of understanding your individual physiology. An athlete with an LTHR of 160 should generally keep most of their easy runs below 140 heart rate (the upper limit of Zone 2). In contrast, an athlete with an LTHR of 180 can push up to 157! Often, these athletes may appear identical in terms of Healthy Survival—same age, same personal records, same training, and same potential. However, their hearts function quite differently.
How to Utilize Your Heart Rate Zones
There are two areas where having a general understanding of your personal heart rate zones can be particularly useful: grasping your Zone 2 (with LT1 as the upper limit) and assessing how long you can maintain an effort. First, let's examine how to approach each of the zones:
- Zone one is perfect for warm-ups, doubles, and recovery runs. For athletes with very high training volumes, almost alleasy runningcould end up in Zone one. For athletes who train at a lower volume, most of their easy runs should likely be in Zone two.
- Zone two is well-suited for uphill training, interval sessions with recovery periods, long runs, and consistent pace runs. For experienced athletes, Zone two can be quite intense, meaning they often need to control the duration spent in this zone to prevent overexertion. For those less experienced, Zone two offers the optimal balance for aerobic and mechanical improvements. In most high-volume training programs, 80-90 percent of the total training should take place in Zone one and Zone two together.
- Zone three is well-suited for trail ascents that require some extra effort, progression runs, and casual threshold intervals or tempos. Specifically for trail runners, spending time in Zone 3 during uphill sections can enhance mechanical efficiency and introduce threshold intensity into the weekly training plan.
- Zone four is well-suited for tempo runs, extended intervals, and most threshold training. During threshold sessions, it's advisable to begin at lower lactate levels and gradually increase the intensity, with experienced athletes typically remaining in Zone three or the lower part of Zone four, while less experienced individuals spend more time in Zone four. Typically, 10-15% of total training should be conducted in Zones three and four together.
- Zone five is suitable for interval training, repetitions, and races, as well as other intense efforts. A smaller portion of your training should take place in Zone 5, with the focus shifting towards enhancing mechanical and neuromuscular output rather than placing significant stress on the aerobic system.
Understanding the cutoff for Zone two can help athletes better gauge what terms like "easy," "steady," and "moderate" truly represent. Checking heart rate occasionally during more intense efforts ensures that athletes don't overexert themselves, avoiding pushing into Zone five and hindering aerobic development. I encourage athletes to become aware of how high their heart rate rises on inclines, as excessive effort on hills can negatively impact endurance and race performance. Zone 3 is a helpful ally when used in balance. Zone 4 is a familiar face. However, spending too much time in Zone five can lead to negative consequences.
Takeaway
The main point is that heart rate serves as an indicator of fatigue, particularly when measured in a laboratory setting. The values can fluctuate daily and differ between training periods. Factors such as temperature, stress, caffeine intake, and political news can influence these numbers significantly, making it unwise to focus excessively on minor changes in beats per minute.
Alternatively, consider heart rate as a method to generally adjust your physical state, checking in on your perceived effort to ensure that your mental perception of your body's activity matches its actual performance. After an athlete becomes familiar with their heart rate, I recommend reviewing it once every few weeks during a run, and only looking at it afterward on other runs (if necessary), without placing too much emphasis on minor fluctuations. Heart rate can be slow to react, so I usually find it not very helpful for shorter intervals.
If you train within the appropriate general intensity range, whether using heart rate, lactate levels, and/or how hard you feel you're working, you can enhance performance at Zone two and Zone three heart rates specifically. Since these efforts are more sustainable from a metabolic standpoint, you'll perform better in races. You definitely don't need a heart rate monitor to reach these goals. However, you do need to develop a strong understanding of your own body's unique responses.
Every one of our bodies can be perfectly tuned realms of possibility. We often just need a small amount of the most attractive element of all: information.
