10:30 miles for 10 miles and staying in zone 1 is impressive. I could never lol. Look up Megan and David Roche. They have a website and a podcast called SWAP.
@GreginPA would recommend not listening to the podcast. I fight through their interesting personalities and humor because they’re on the leading edge of all things running and most things fitness wise. She’s got her MD/PhD in like women’s athlete science. They’re both coaches and they both throw down racing efforts at paces and HRs I never could have imagined were possible at insane distances and elevation. Greg couldn’t stand his voice but they’re a wealth of knowledge. Read their articles if you can’t do the podcast. I’m still learning and pretty sure I had my zone 2 too low before this injury. I still was getting a lot of miles down and massively improving my 5K/10k/half times.
Apologies in advance to everyone who doesn’t care about this but here’s from a 2024 article from their patreon:
“Your physiology is beautifully unique. I sound like John Mayer if he was a physical therapist. Our bodies are wonderlands, even if our glutes are unmaintained landfills.
This is an aside, but "engaging your glutes" is the one pet peeve I have in PT language. Yes, a running form that is tall through the hips and doesn't excessively recruit quad muscles is good. But I promise, my glutes are engaged or I'd immediately fall on the ground. MY GLUTES ARE ENGAGED, DAMMIT! You can tell I have been glute-shamed.
The individual uniqueness of athletes creates a problem, though. How can we understand our physiology in the broader context of training theory when every variable is a bell curve across the population? General equations work if you’re smack-dab in the middle of the bell curve thiccness, but can be actively wrong and counterproductive as you venture into the standard deviation hinterlands.
On the podcast this week, we mentioned the flow-charts of physiological processes that would take up entire walls if they were diagrammed out. But realistically, something like heart rate would take up an entire football field! You can think of it almost like a Plinko game from The Price is Right, hitting so many branches on the way down that it can be tough to be sure what is driving the final zones. In other words, the zones are helpful because they summarize 1000s of variables, many of which we could measure, most of which we couldn't even if we knew what they were.
Consider the equation that many of you might have heard about heart rate: 180 beats per minute minus age = approximately aerobic threshold, or the intensity level that serves as a top-end barrier for easy/steady running that should encompass around 80% of your training volume. While that equation is generally useful, it can be actively useless for individuals, especially aging athletes who are highly trained and have a much higher aerobic threshold than the equation would predict.
For me, the equation caps my easy runs at 145 heart rate. My actual aerobic threshold is 152 beats per minute in running (and 150 beats per minute in biking). In practice, that’s almost a 1 minute per mile difference in output. Training from a general equation would prevent me from accruing benefits from steadier paces, and I’d probably be slower at everything.
Any my heart rate is pretty close to the middle of the bell curve! It's even worse when using the old 220-age equation for max heart rate, which returns some wildly disparate zones and might as well be a random number generator.
Training zones from your watch can also be atrocious. A lesson I have learned calculating hundreds of heart rate zone charts is that some of the watch brands use algorithms that are less accurate than U2 in Spanish class. Zone Uno, Zone Dos, Zone Tres, Zone Catorce, Zone Biblioteca, etc. Some of the watch zones are set so low that I have no idea what they could possibly be measuring.
Coros, I'm looking at you. Their wrist sensors are hilarious. HOWEVER, the Coros slander can stop now because it seems like their arm-strap monitors are wonderful. That may be the new frontier here--arm straps. If your wrist monitor sucks and a chest strap is too invasive, try an arm band monitor.
So today, let’s look at one simple way to calculate your heart rate zones to help you calibrate your training intensity. Knowing your intensity ranges is helpful because it optimizes your metabolic fitness, allowing the body to burn more fat at higher outputs, while supporting mitochondrial proliferation and efficiency, allowing both higher and lower intensities to take less energy. Disclaimer: exercise physiology terminology is always subject to evolving debate, particularly on Twitter (the world’s town square, if the square was also where the town put the raw sewage). Here is
my favorite infographic ever on the overlap of these principles, from Fluid Athletics (
follow them on Instagram here).
This infographic saves lives!!!! But even within that infographic, there would be debate on Twitter, with people getting precious as hell with their exact terms. My god subcultures can be frustrating sometimes.
Zone Background
We’ll be using the traditional 5-Zone model, contrasted with the 3-Zone model used in most training research, but it helps to understand both and how they interact.
It's pretty funny reading my articles over again how I feel the need to go 10 steps farther than necessary. You know what would save your time, David? Write a traditional 800-word article and go on with your day. I'd probably write 5000 words about how to wipe in the woods if I tried that article.
Heart rate is best thought of as a proxy for lactate concentrations. To simplify it a ton, lactate is produced as our bodies use glucose to fuel ATP production during glycolysis. Lactate is a fuel source for cells, and it’s accompanied by a hydrogen ion that changes muscle pH and contributes to fatigue. A
2018 review in
Cell Metabolism described the lactate shuttle where the cells use lactate for energy. If this shuttling mechanism is overstressed, lactate levels and fatigue rise and exercise becomes less sustainable. A
great overview by Dr. Howard Luks is here.
For this next breakdown, refer back to the Fluid Athletics figure at the top of the page! It really helps with orienting in the zones.
When lactate concentrations begin to rise, intensity switches from easy to moderate, an inflection point known as LT1, broadly overlapping with aerobic threshold where athletes go from primarily burning fat to primarily burning glycogen. And when lactate levels rise more steeply at higher intensities, intensity transitions from moderate to hard, an inflection point known as LT2, broadly overlapping with traditional lactate threshold (or critical velocity, depending on the method of calculation). That encompasses the 3-Zone model used in research:
- Zone 1: under LT1, or ~2 mmol of lactate with individual variance (think very easy running up to more steady running for advanced athletes)
- Zone 2: between LT1 and LT2, generally between ~2 and 4 mmol of lactate (think steady running to traditional threshold, or approximately 1-hour effort or a bit harder)
- Zone 3: above LT2 (think faster intervals and harder hill work)
Those zones are used in research to determine intensity distribution. While these breakdowns are gross approximations, it can help to put some numbers on paper to get your bearings (all of these numbers have big error bars).
- A Pyramidal model used by most elite athletes usually entails ~75-85% in easy Zone 1, ~10-20% in moderate Zone 2, and ~5-10% in hard Zone 3
- A Polarized model entails ~75-85% in easy Zone 1, ~5-10% in moderate Zone 2, and ~10-15% in hard Zone 3
- A Threshold model like some describe “Norwegian” training entails ~60-75% in easy Zone 1, ~20-30% in moderate Zone 2, and a small proportion in hard Zone 3
SWAP training is generally Polarized as athletes start out and build up, and Pyramidal in advanced athletes. Most weekly speed workouts are in Z3 in a 5-Zone model, long runs in Z1/Z2, and strides in Z3, with the remainder in Z1.
So if we’re using heart rate to approximate lactate and the associated physiological impacts of fatigue, why don’t we just use lactate? Good question, you article-ruining jerk. In a perfect world, athletes may decide to prick themselves for blood lactate readings with every interval like they’re Norwegian vampires. Practically, though, there’s a lactate learning curve in the best of times that can lead to inaccurate data, and in the worst of times it can take some of the spontaneous artistry out of daily training. You can probably tell I’m scared of blood, needles, and vampires (whether traditional or sexy).
We love experimenting with lactate meters though! In general, simple protocols of 1200 meter intervals can get you a solid estimation of paces associated with zones, which is especially useful for track and road runners.
But have blood-free hope! Using the method in the article, I have approximated zones for professional athletes that have later been validated in lab tests with small enough margins of error to be useful. However, it’s key to get a full lab test for truly accurate data. Heart rate without lactate, metabolic, and/or ventilatory lab tests is like determining the time from where the sun is in the sky. With context clues, you can be close, but you wouldn’t want to use it to cook a turkey.
Screw that, I can cook turkeys based on my estimations! With one pro we coach, I got within 1 beat per minute and 1 second per mile for LT1 and LT2. Where's my Nobel?! You can do that too with this method.
5-Zone Training Model
Now, let’s finally get to the 5-Zone heart rate model that is used in most training approaches. The 3-Zone model is overlaid with bold, italics, and regular font (again, there is debate around the exact breakdown, particularly with the Zone 3/Zone 4 delineation).
- Zone 1: purely easy/recovery/regeneration, burning primarily fat, with little lactate production. Athletes can talk in full conversations and go almost all day with appropriate fueling/hydration and training.
- Zone 2: easy to up to steady, capped on the top end by LT1, where the body begins to produce more lactate and ventilation rate increases. The top end of Zone 2 can be sustained for many hours, with variance based on athlete training.
- Zone 3: moderate up to moderately hard, sometimes called tempo. Athletes can talk in sentences, and often it feels relaxed, sometimes sustainable for up to a few hours with plenty of fueling.
- Zone 4: moderately hard threshold training. For our purposes, the top end of Zone 4 is capped by LT2, though some approaches have it occurring lower. Athletes can talk in clipped sentences and sustain the top-end effort for around 30-60 minutes, depending on the exact approach to setting the zone.
- Zone 5: hard or fast intervals, often termed VO2 max or repetitions. This is a broad zone consisting of most intense intervals and harder pushes, and it’s broken down into more zones in some approaches.
I am saying the word Zone so much that it has lost all meaning.
There are a few ways to set the zones, but I see the most repeatability and accuracy with the Lactate Threshold Heart Rate method pioneered by legendary coach Joe Friel.
As outlined in Training Peaks, he suggests that athletes “do a 30-minute time trial all by yourself (no training partners and not in a race). Again, it should be done
as if it was a race for the entire 30 minutes. But at 10 minutes into the test, click the lap button on your heart rate monitor. When done, look to see what your average heart rate was for the last 20 minutes.”
Fun fact: Joe Friel reached out to us in the summer to feature SWAP in his coaching education platform! Here is that collaboration, with another here.
I like athletes to do the test on uphills, where they won’t be limited by neuromuscular and biomechanical factors if they don’t have a ton of speed training. If it wasn’t a truly hard effort or your heart rate takes a lot of time to increase across an effort, you can take the average heart rate from a section as short as 10 minutes. Because this isn’t an exact measurement like in a lab test, think of it as an art that is useful in understanding your body, rather than attempting to find a correct answer like high school algebra.
For an easy way to scrub complex data files with HR variation, you can use the
Strava Sauce browser plug-in, highlight the area you want to examine, and it will give averages without ever lapping the watch. When I calculate zones for athletes, I have found that you can also approximate LTHR from almost any hard workout with intervals 3 minutes or over by looking for spots in the file where heart rate stabilizes for 15-30 seconds before rising to less sustainable levels (and sometimes falling back toward that baseline in longer efforts). Be careful about using data from very hot days or long races over 90 minutes, when heart rate can sometimes be sustained above Friel’s LTHR in ways that are not mirrored by the underlying physiology.
Here is where the art becomes a learned skill, and we are here to help! If the heart rate is increasing across the tempo, it's likely that the LTHR is higher than the average. If it peaks and stabilizes or goes down, it might be a bit lower. Using intervals, we're generally looking for a stable HR graph which then might go down a beat or two, but if it goes above that, the output suffers or HR goes even higher.
A big key here: the data needs to be accurate. Chest-straps or arm bands are ideal for these purposes, and if you are doing a workout to set heart rate zones, it’s worth using the chest strap even if it feels like you’re getting the heimlich maneuver from a weak octopus. While wrist-straps are rapidly improving in accuracy, there is extreme variation among athletes/watch brands. For example, my Garmin 745 seems to work really well in most circumstances (
see this beautiful graph of a threshold workout). But other athletes don’t have that success, and sometimes they send me heart rate files that look like Bitcoin price graphs (we are not sure why it’s going up and down, but we can be pretty sure it’s nefarious).
Now, there's a Bitcoin ETF! The market has spoken!
Setting Your Zones
Once you have the LTHR number, it’s time to set those elusive zones. We’re at another controversial point where the exact percentages are subject to extreme debate. The problem: when you validate heart rate data with lab tests, individual physiology varies substantially. LTHR narrows down that physiological variation to get an idea of zones, but the exact delineation depends on training history, muscle fiber typology, metabolic context, astrological sign, etc. Don’t even get me started on Scorpios.
Leo is a Scorpio. When we were in the hospital getting ready for Megan to give birth, a nurse said "I am so sorry about the date." "Why?" we responded. "Male scorpios are nightmares," she said.
Here are the percentages that Megan and I like to use:
- Zone 1: under 80% of LTHR
- Zone 2: 80% to 88% of LTHR
- Zone 3: 89% to 94% of LTHR
- Zone 4: 95% to 100% of LTHR
- Zone 5: above LTHR
The one place we'll sometimes see differences is very advanced athletes might have Z2 a bit lower, like 85% of LTHR.
Let’s dig into an example from my data. In February,
I did a virtual bike race up a mountain.
The only races that matter?
Using the Strava Sauce plug-in and highlighting the final 20 minutes of that hard effort, my LTHR was 172. While there is variance across sports and my heart rate is higher with running, that means my current zones for biking are approximately:
- Zone 1: under 137 beats per minute
- Zone 2: 137-150 beats per minute
- Zone 3: 151-161 beats per minute
- Zone 4: 162-172 beats per minute
- Zone 5: above 172 beats per minute
Your LTHR may increase with training and it will drop with age. Athletes are often between 165 and 175, though in professional athletes, I have seen numbers as high as 189 and as low as 152. You can see why dialing in your unique physiology is so important. An athlete with an LTHR of 160 needs to cap most of their easy runs at 140 heart rate (top end of Zone 2). Meanwhile, an athlete with an LTHR of 180 can go all the way up to 157! Often, everything about those athletes can look the same from the outside--same age, same PRs, same training, same potential. But they have very different hearts.
And one final complication is how LTHR can change over a season. That's why these numbers cannot be gospel--one study showed elite cyclists can have this number shift by 3-7 beats per minute, with aerobic threshold not moving perfectly in tandem. And in fatigued states, HR can be depressed (with the reverse true when rested). View everything as a range that changes day to day and especially month to month, rather than a hard cap or rule.
How To Use Your Zones
There are two places where having a general feel for your personal heart rate zones can be most helpful: understanding your Zone 2 (with LT1 as a cap) and determining the sustainability of longer efforts. First, let’s break down how to think about each of the zones:
- Zone 1 is ideal for warm-ups, doubles, and recovery runs. For very high volume athletes, almost all easy running may end up being in Zone 1. For low volume athletes, more of the easy running should probably be in Zone 2.
- Zone 2 is ideal for uphills, floats between intervals, long runs, and steady runs. For advanced athletes, Zone 2 can be quite fast, so they often need to limit the time in this zone to avoid breakdown. For less advanced athletes, Zone 2 is the sweet spot of aerobic and mechanical adaptations. In most higher-volume training systems, 80-90% of total volume should be in Zone 1 and Zone 2 combined.
- Zone 3 is ideal for trail uphills involving a bit more pushing, progression runs, and relaxed threshold intervals/tempos. For trail runners in particular, Zone 3 time on uphills can improve mechanical output and add threshold intensity to the weekly distribution.
- Zone 4 is ideal for tempo running, longer intervals, and most threshold training. When doing threshold work, it’s better to start at lower lactate concentrations and build into the effort, with advanced athletes often staying in Zone 3/low Zone 4, and less advanced athletes spending more time in Zone 4. Usually 10-15% of training volume should be in Zones 3 and 4 combined.
- Zone 5 is ideal for intervals and repetitions, plus races and other hard efforts. A smaller percentage of training should be in Zone 5, with time in this zone focusing more on improving mechanical/neuromuscular output than aerobic system stress.
Knowing that Zone 2 cutoff can help calibrate an athlete’s effort so they understand what terms like “easy,” “steady,” and “moderate” actually mean. Spot-checking heart rate periodically on harder efforts can ensure that athletes aren’t going too hard, pushing everything into Zone 5 and reducing aerobic adaptations. I love athletes to get a feel for how high their heart rate gets on uphills especially, since excessive effort on ups can lead to reduced endurance and race performance. Zone 3 is your friend, in moderation. Zone 4 is your acquaintance. And spending too much time with Zone 5 will end with you folded up in a car trunk somewhere outside Las Vegas.
Sounds like a fun party to me!
Takeaway
The big takeaway is that heart rate is just a proxy for fatigue processes, especially when calculated outside of a lab. The numbers can vary by the day, and they change across training blocks. Temperature, stress, caffeine, and political news all impact the numbers enough that caring too much about a few beats per minute is unhelpful. The day I first heard the nickname “Meatball Ron,” I was in Zone 3 while sitting on the couch.
DeSantis wore platform shoes, and given the height discussion on the podcast this week, you should know I empathize with him. He should have just worn HOKA Bondis!
Instead, view heart rate as a way to calibrate your physiology in a general way, spot-checking your perceived exertion so that you know what you think your body is doing generally aligns with what your body is actually doing. Once an athlete dials in heart rate, I like them to look at it once every couple weeks during a run, and solely after-the-fact on other runs (if at all), never investing too much in small changes. Heart rate sometimes takes a while to respond, so I find it’s rarely useful on shorter intervals.
If you train within the correct general range of intensities, whether guided by heart rate, lactate, and/or perceived exertion, you can improve output at Zone 2 and Zone 3 heart rates in particular, and because those efforts are more sustainable metabolically, you’ll excel in races. You definitely don’t need to have a heart rate monitor to achieve those goals. But you do need to have a good feel for your unique physiology.
All of our bodies can be well-calibrated wonderlands. We sometimes just need a little bit of the most sexy thing of all: data.”
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