This essay will diverge a little bit from the content I usually publish here. Keep reading if you want to take a dive into the world of distance running and how its hottest training approach compares to one of cycling’s hottest.
Double-threshold training hit the big time in the running community after the training program of Norwegian Jakob Ingebrigsten (Tokyo 2020 Olympic 1,500m champion at age 20) under his coach at the time (his father Gjert) was (mostly) revealed to the public. The program was copied directly from Marius Bakken, a Norwegian international runner in the 2000s, who, to my knowledge was the first adopter of lactate monitoring in the distance running world.
Zone 2 training has been quite mainstream in endurance sports for decades, but it exploded into the broader health and wellness discourse, and even into mainstream media in the summer of 2023 with big health “influencers” like Andrew Huberman and Peter Attia hyping Zone 2 to the moon on their platforms (Disclaimer: I adhere to many of Huberman’s protocols). Inigo San Milan of Spain, arguably the world’s leading proponent of Zone 2 for not only performance but also health, coaches the UAE Team Emirates cycling team which won the UCI team ranking in 2023. More importantly, San Milan’s training stable includes the number-one ranked rider on Earth for three years running (including two victories in the Tour de France) Tadej Pogacar of Slovenia. So clearly, Zone 2 also has some proven results.
But let’s backtrack here and discuss what exactly these terms mean.
“Double threshold” is a component of the Norwegian training model, in which one completes two interval sessions in one day (with perhaps 6-8 hours in between sessions) at a moderate intensity, in simple formats like 10×3 minutes, 5×6 minutes, 25×400 meters, etc. In the Norwegian program, the athlete performs two double threshold days per week, for a total of four sessions every seven days.
What exactly is the pace or intensity of the double-T intervals? Well, that is not the simplest question to answer. In Norway, the paces are tightly controlled by lactate monitors (thus varying from day to day), which take a blood sample from the athlete after one of his or her intervals and spit out a lactate reading (this is a measure of lactate concentration in the blood in millimoles per liter. In layman’s terms, lactate is a measure of one’s exertion level). The goal lactate figure for trained athletes executing a double threshold session is 2.5-4 mmol (which is a massive range) depending on the individual and the “type” of threshold session (yes, there are different ways to get the same lactate stimulus). This could also be described as between lower Zone 3 and upper Zone 4 intensity.
On the lower end, 2.5 mmol might correspond to the pace one could race a marathon or a little further at, while 4 mmol might be closer to 10-kilometer race pace (corresponding heart rate figures would be between 80ish and 93ish percent of one’s maximum.) For the type of athletes we are discussing here, a marathon shouldn’t take much more than 2 hours to complete (4:35ish/mile or 2:50/km pace), while a 10k requires 27 or fewer minutes (sub-4:20/mile or 2:40/km pace). That’s not a massive range of paces for a massive range of duration of the “effort” (race pace) in question. But these athletes, particularly Jakob, have built such enormous aerobic engines that they *theoretically* could hold an absurd pace for an absurd duration at low lactate numbers.
Usually, the athlete would do the slower-paced session in the morning; for example, 5×2 kilometers or 6 minutes on 2 minutes rest at marathon pace or 2.5 mmol, and the faster-paced session in the afternoon, like 25×400 on 45 seconds rest at around 10k pace to get closer to 4 mmol at the end of the session. That is what people mean when they talk about “Norwegian” training, or say “double threshold.” In reality, the correct interpretation and application of the model is more complex than simply doing four Z3/Z4 interval sessions per week. But we’ll get to that.
“Zone 2” training is a little bit simpler in that it just describes a single training intensity. There are of course multiple definitions for Zone 2 intensity, but essentially it’s a comfortably hard pace that a decently-trained athlete could hold for four hours (though in running four hours is probably a bit unrealistic due to the muscular-skeletal abuse involved) or so, but probably closer to eight hours for elite cyclists.
Cyclists use a power-based definition for Zone 2, as a percentage of Functional Threshold Power (which is considered the wattage the rider could hold for one hour). TrainerRoad defines Z2 as “55-75 percent of FTP”. 55 is way too low in my view; 65-75 sounds more accurate to me, at least if Z2 is the main feature of one’s training program. So if the athlete’s FTP was 400 watts, Z2 would be 260-300 watts.
In running, most people use pace charts, based on Personal Bests in races to calculate their Z2. Jack Daniels created a simple (but extensive) table for calculating your “Easy” (he means Z2 by “E”) pace by inputting your race results. So if you had a 5k PR of 15:00 (3:00/km or 4:49/mile pace), your supposed “E” pace might be about 6:25/mile or 4:00/km pace. I know a heck of a lot of 15-minute guys (I am one myself with literally 15:00 on the board) and some who are significantly under. They (and I) didn’t get there by going out and trying to run 6:25 pace every day. I had a spell in my own running career in which was averaging about 5:50-6:20 every day for “Zone 2” with a low HR (for me) and feeling good enough doing it. But in reality, I was pushing into Z3 every day and overcooking myself. I followed up that training block with a personal-worst 10k in my adult life. I’ve seen so many runners, and some cyclists, train this way and either plateau for years or regress. It does not work. It never will. I call it the Grey Zone: too hard to recover from, too easy to gain from, specially when coupled with a lack of structured quality training.
Why do most runners go too hard on Z2 efforts, often without knowing it? Daniels’ “E” pace is notoriously aggressive. So when a world-renowned exercise physiologist tells you to run hard every day, a lot of people listen. But I want to add in a brief defense of Mr. Daniels. If you actually read his Daniels’ Running Formula cover-to-cover, you will find that he does stress running under control and keeping “E” pace easy with his words. But his charts do the opposite, so most people see a pace and think they have to hit it or beat it every day to get fast. No.
Overdoing Z2 in running is both extremely easy to do day after day and arguably the most self-destructive (because it’s physiologically and emotionally addictive, especially in the age of Strava, as one can gloat every single day, sometimes twice per day, about how fast they are for the public to see) training habit in the broad universe of horrendous training approaches.
So I disagree with Daniels’ “E” guidelines approach for a multitude of reasons. The first is that it assumes you are in PR shape every time you set out the door for a standard run. You’re not. Next, it is not going to be possible to emulate perfect race conditions on almost any run (weather, shoes, running surface, rabbits, etc.). The difference between a track and a trail is significant by itself, let alone if it’s 90 degrees out when your PR was run in 55 degrees. We could be talking about over a minute per mile difference here, at least for Z2 heart rate. Then, Daniels’ “E” pace assumes not only linear ability in all distance events (in layman’s terms, equal speed and endurance), but also an incredible level of base aerobic fitness. Essentially, the problem with that is that most athletes are not even close to fit enough to keep their heart rate in the proper zone at the given pace. This means they will be pushing Z3 every day and in continuous runs, as opposed to intervals, which is even more taxing. This destroys the metabolic system (as well be expounded upon later), ability to produce lactate as fuel (which is an underrated ability for well-trained runners), and kills the legs for when they are needed to hit a real quality day.
If any more sophisticated data is available, I would not use pace for Z2 guidelines. Heart rate is a decent start, but lactate testing is the gold standard in contemporary training. That is probably not doable for most runners, so heart rate it is. Anyways, that’s my rant on Z2 in running over for now.
Proper Z2 training ought to generate perhaps 72-78 percent of one’s maximum heart rate (some experts say lower, while Attia, for example, says 80). Corresponding lactate figures, according to San Milan, are 1.7-1.9 mmol. However, I have never heard of anybody using lactate to test on Zone 2 efforts (that being said, it’s probably a good idea for a lot of people who tend to overtrain!)
Okay, so now that we have the basic terminology and my own definitions out of the way, let’s get to the thesis of this essay and why it needs to be written: Zone 2 Training and Double Threshold (AKA the Norwegian Approach) are almost polar opposites! You cannot do both. Perhaps just as unique within the Norwegian Approach as its use of double threshold sessions is its near-total omission of standard Z2 running. On the flip side, almost as novel with Z2 training is its near-total omission of Z1 and Z4 training.
So let’s take a deep dive into a comparison of the Norwegian Approach, as applied by the Ingebrigstens (and revealed to the public in part by Jan Bengtsson, who claims to have “copied” Gjert’s schedule and used it to coach Swedish athlete Kalle Berglund to a 3:33 1,500m, among other achievements) and the Zone 2 model, as applied by UAE Team Emirates cyclist Brandon McNulty (at the direction of San Milan). By extrapolation, we can assume Pogacar is doing similar training to McNulty. Jakob is the best runner in the world, and Tadej is the best cyclist. They get incredible results out of themselves, especially from such a young age, and with opposite approaches. That makes this an exciting contrasting topic.
It should be noted at the outset that I (and I would wager that almost everybody interested enough in this sort of thing to be reading this, or reading the LetsRun message board, etc) is operating on limited information. We just do not know what Jakob’s pre-competition phase, in particular, looks like. Nor do we know exactly what Tadej is doing for wattage anymore, as he does not share much on Strava anymore, and when he does, the power is hidden.
I wrote a long post on this blog about McNulty’s training and racing leading to his victory in the Volta a la Communitat Valenciana (a second-category, but highly competitive race in Spain).
But for those who do not want to go back and read that entire essay: I’ll summarize it now: In the 12 weeks leading up to and including the Volta. McNulty did a medium volume of total riding for a WorldTour pro in the winter, averaging about 19 hours per week without any big peaks or valleys in his workload. His rides were mostly between 2 and 4 hours, with only two over 5 hours. He did almost all of his daily rides in Z2, which for him is 240-290ish watts; usually around 270. His interval sessions are almost all long lower Z3 efforts, often doing 3×45 minutes at 310-330 watts. He did a few over/under sessions which could be categorized as Ronnestad or Billat-style VO2 max intervals (40/20s or 30/30s in 6-8 minute blocks) in which he hid his power data on Strava. But the overs were probably done in Z6 and/or Z7, and the unders probably around lower Z3. He never did traditional 3-5-minute VO2 max (Z5) intervals. His “warm-ups” and “cool-downs” from his intervals were also done in Z2, adding to the training stress of those rides. Sometimes his “cool down” was an hour or more at 295 watts with just a few minutes of cruising at 190 watts to finish the ride. (I know how it feels to have the legs opened up from some intervals and suddenly upper Z2/lower Z3 feels too easy. I have to imagine that at the beginning of his training cycle, 295 for the last hour was just him feeling a bit frisky.) He only did Z1 about once per week for shorter rides (usually about 90 minutes or less). He did almost no Z4 work, except for one session in which he did 2×20 minutes with cycles of 4 minutes between 400 and 425 watts and 1 minute at 500-plus watts done continuously. The 4-minute reps were probably in Z4. He also took a day or two off every week, which Jakob does not schedule in his training.
But the main point is that the vast, vast majority of McNulty’s time on the bike was spent in Zone 2. That seems to work to build his massive aerobic engine as well as develop his VO2 max and anaerobic engine. For example, he made an impressive 6.5-minute effort on the Queen Stage of Valencia, pushing 513 watts (7.4 watts per kilogram) to start a 16ish-minute climb, on which he won the stage and took the GC lead. The conclusion to be drawn here is that the Zone 2 program (including its tiny dose of HIIT-type over-unders) is not just for “Base”/GPP training. It actually can get one to an extremely high level of anaerobic fitness, too.
Meanwhile, from what we know about Jakob Ingebrigsten’s base training, double threshold is of course the focal point of the week. But do you know what he spends a lot more time doing? Running in Zone 1. Jakob is now known to run up to 200 kilometers (124 miles) per week in his base phase. Humans as we know them, at least thus far, cannot grind out even close to 50 miles of “threshold” in a week. My best guess is that he peaks out around 50 kilometers (31 miles) of threshold per week based on 12ish kilometers multiplied by 4, which may even be too high an estimate. It is certainly more than most elite (non-African and/or non-doped) runners have done up to this point, especially middle-distance runners. I want to finally mention that Jakob does 2x10x200 meter hills every week in the base phase at a pretty high intensity (probably 800-meter effort) on Saturdays (the double-threshold days are Tuesday and Thursday). But 20×200 is only 4 kilometers, 8 if you count the jogs down the hill.
20×30 second hills at a lactate figure around 10+ (probably not far off his max heart rate by the end of the workout) is quite similar to the over/unders performed by McNulty this winter. Jakob also does not do traditional VO2 max intervals of 3-5 minutes, at least not in the base phase. 10 minutes of work in Z6/Z7 at a high lactate figure (in addition to improving running economy and neuromuscular power) provides a great anaerobic stimulus without going to the well with a session such as 5x1k at 3k race pace. That’s not to say Jakob never does work like that, but he does not ever do it during winters/GPP (General Preparation Phase).
But what the hell is he doing with the other more than 142k (90ish miles) of his training each week? Well, because he has three days of workouts per week, a lot of time and miles are spent warming up and cooling down. He is known to never jog in between threshold reps, which would be an easy way to top up weekly mileage. I have to assume that warm-ups and cool-downs are all done in Z1. Say he warms up 5k and cools down 3k from every session. Suddenly we are looking at a lot of miles. Wednesday and Friday are recovery days. The last time his schedule was discussed, it was explained that he doubles with 10k runs in the morning and afternoon at a very light effort. I would imagine that he has bumped up the length of those runs as his total mileage increased.
The only exception to the anti-Z2 bent in the Norwegian method is the Sunday “long run” which in European training programs is almost always 20 kilometers for non-marathon runners. To American observers, that is a very short long run for a guy who is a double 5,000-meter world champion. It’s made even shorter because Jakob does this run as quickly as 70 minutes or less, which is under 3:30/km or 5:40/mile pace. That is a decent Z2 effort for a 7:54 2-miler/12:48 5k runner. It may even be too easy for true Z2, but I don’t think Jakob is worried much about that, nor is he worried about not pounding out 2-hour runs every week. It’s not the focus of his base training; hitting a huge volume of threshold and getting in massive minutes in Z1 is.
Why Z1 instead of Z2? Well, Z1 has a few advantages in the context of a big-volume training approach. It is often referred to as “recovery” by runners and cyclists alike, and it certainly is easier on the legs than Z2, but Z1 has another benefit that most people overlook. It promotes the body’s metabolic efficiency, which essentially means it helps an athlete burn more fat at all intensities. This is probably more important for WorldTour cyclists, whose races are sometimes 6-plus-hour, 7,000-kilojoule marathons (meaning they need to spare glycogen as much as possible) than middle-distance track runners, whose races max out at around 13 minutes, but I would not underestimate it as a huge part of why Jakob is so good. His ability to preserve his glycogen stores throughout a week of hard training means that he has more left in the gas tank when he needs to go hard, like on those 200m hill reps. The caloric output of a 35-ish kilometer double-threshold day, while nowhere near that of a long Z3 training session on the bike in the context of a six-hour ride, is pretty high (likely well over 2,000 KJ), and at that intensity, most people are going to burn almost exclusively glycogen as opposed to fat. It’s well-established in the scientific literature that the body can only store 2,000 to 2,500 KJ of glycogen at any time, but essentially unlimited KJ of fat. Doing two double-Ts per week would burn through Jakob’s glycogen stores both times, if not for all of the Z1 training improving his body’s ability to use fat as fuel at all paces.
The obvious riposte to that diatribe is “Why wouldn’t he just eat more carbs?” Well, that’s an option too. However, it can lead to metabolic inefficiency, and it makes it more difficult for even an elite athlete running 120+ miles per week to obtain the optimal body composition (read: an incredibly low body fat percentage, and in distance runners and cyclists, no upper body mass at all). Jakob was noticeably skinnier during the 2023 season than ever before. Last year, he did things like run a 7:54 2-mile world record in what is one of the most incredible feats of endurance sport of all time. Losing fat makes you run faster. Z1 training is the fat-burning zone.
Much of my learning on this topic has come recently from Alan Couzens’ Twitter feed. He is a true expert on metabolic health, and I believe he still coaches elite triathletes. I’d check that out for a very different take on endurance sports training and physiology than is often discussed.
Many of you are probably screaming right now: “You’re comparing apples to oranges! The physiological demands of a professional bike race versus an Olympic 5,000-meter race are quite different. One can demand up to 7,000 KJ, the other maybe 400. Also, Zone 2 is more effective for cyclists because of the volume one can do on the bike compared to in running, where one kind of needs to maximize the time spent on feet.”
I hear that. The next step in the opposing argument would go something like this: Zone 2 intensity mimics more closely the average power of a professional bike race. The Norwegian model, on paper, makes little sense for a cyclist who doesn’t need to do double sessions, he or she can simply bang out 2-3 hours of Z3 in one ride. Meanwhile, runners cannot put in enough Z2 volume to make it as effective as the Norwegian approach, and Zone 2 is not “specific” to any racing intensity except maybe for ultrarunners.
I’ve been synthesizing a response for a while now as this essay grew in my head: I believe Zone 2 training can be almost equally effective in running as it is in cycling, provided one’s training volume is extremely high (high being 12 hours of running per week or more… and bring the pitchforks out and flame me, but cross-training on top of high mileage is a good idea if Zone 2 is the approach, even if running fast in 1,500m-5,000m is the only objective). I also would argue that while double-threshold work in cycling is utterly untested as far as I know, it has incredible potential. Logically, with a 6-8-hour recovery buffer in between the double-threshold sessions on the bike, one could put in a little bit more volume of Z3/Z4 on their quality days than if they just crammed it into one ride.
But if somebody wanted to try to go all-in on Zone 2 in running, the focus would be on putting in huge miles and lots of aerobic cross-training (cycling being the best option) on top of that, so building volume as quickly as is safe to do so The runner would also want to do the long Z3 intervals at a carefully monitored intensity. Of course, 3×45 minutes is impossible in running, but one could do 3×25 minutes in lower Z3 within a longer run, for example (this is not a new idea, it is largely drawing from what Arthur Lydiard discovered 60 years ago). The over/unders would be done as 200on/200float (AKA the Oregon Drill) in 1,600-meter blocks, with 2 minutes of easy jogging or walking recovery in between blocks (nor is this a radical workout; runners have been doing that for 50 years and I credit Bill Bowerman with inventing this particular session). But in general, I would absolutely love to see a runner attempt this Z2 approach.
If a cyclist wanted to try the Norwegian approach and mimic how the runners do it, I do not see a reason that could not be done, with minor tweaks. Bike riders are not going to shorten their recovery rides and double up on Wednesdays and Fridays, so that could be done as one longer Z1 ride. However, the double threshold sessions need to be done in separate rides. The 20×200-meter hills could just be 2x(10×30/30s) as over/under blocks. The Sunday “Long Ride” could be 3 hours in Zone 2. The rider could throw in a few alactic sprints of 4-8 seconds at maximum watts with full recovery (3+minutes spinning easy) at the end of their Z1 rides, too. The total volume of riding would be a bit lower than the Z2 program, but the volume of intensity would be higher.
And that is the age-old debate: Quality vs. Quantity. The answer, of course, is both. But when one stretches their time and recovery abilities to the limit, which one should be the priority? That depends on a complex pyramid of factors including genetics, training history, race objectives, and more. Everyone has to come to their own conclusion based on all of the available information.
So, between Norwegian and Zone 2, which approach is better? Before the answer, I need to stress that both protocols hinge delicately on discipline: discipline to put in big total volume, discipline to train in the proper zone at all times, discipline to recover with good lifestyle choices, and discipline to put it all on the line on race day. Endurance training and racing is brutally hard. Both of these methods are going to induce a lot of physical and emotional distress, even if the intensity is carefully controlled every second. Runners and cyclists already know this. But if you want to maximize your potential, every aspect of one’s life must be evaluated in terms of its relation to endurance performance.
That brings me to the final aside regarding both training approaches. Most humans, sadly still, even in the Western world, are a bit hamstrung for time to exercise. If they make time, it’s not a priority. That is bizarre; humans evolved to move, and move a lot. For 99.99 percent of human history, we had to move to survive. We naturally stayed fit. Advanced economies have offered great things, modern medicine chief among them (which has essentially doubled lifespans in just a century-and-a-half). But the advanced, and now even the developing world, has a serious problem with not only obesity, but lethargy and sedentary lifestyles (even if you’re skinny). It’s extremely unnatural, and of course unhealthy, to not perform a lot of physical activity every day. The point here is that two things need to change: We need to set up our society so that (a lot of) exercise is possible for everyone. Every day. And we need to change the majority of minds so that people actually make it a top priority.
This is to say that professional athletes (and the rich who want to make this a passion project) have a massive advantage when choosing which of these two approaches to take. As has always been true in all things, with time and money, incredible achievements are more likely. Pros have more time to recover and more resources to utilize in training (like weight rooms, tracks, treadmills, etc). That is not the case for the average person.Thus, every human who wants to dive into Zone 2 or Norway’s training system, in running or cycling, needs to figure out how they can fit the training into their existing life. And it’s just never going to work as well unless you are doing high volume. All that being said, I believe that people make time for what they care about. And if you truly want to maximize your potential as an endurance athlete, you’re going to have to spend a lot of time training. In some ways, it could not be more simple. But it also could not be more difficult.
Okay, so now it’s time for my verdict: I feel more comfortable with Norway’s philosophy, but I come originally from the running world. Knowing what we currently know, and based on proven results, I would advise every slow-twitch runner (which is the vast majority of distance runners), beginner or experienced, to adopt the Norwegian approach (of course, one needs to adapt the program to one’s current training level. You cannot just jump into 24 kilometers of threshold training done twice per week. Build up volume gradually).
In cycling, if I were put in charge of a UCI WorldTeam, especially if it was Movistar (lol), I would implement the Norwegian model there as I described above. There would not be much to lose for the Spanish team if it did not work 🙂 I kid, but really, I should note that Visma-Lease a Bike (the team that won all three Grand Tours last year) is doing double rides occasionally this off-season, but they are quite secretive with their power data, so I cannot tell what intervals they are doing. They may well be experimenting with a bit of the Norwegian model on the bike. If they are, and it works, they are going to be even more dominant in 2024.
In 10 years, every athlete with a serious coach is going to be utilizing Continuous Lactate Monitors, which will be a patch on one’s arm that gives real-time lactate data to the athlete so they can always be in the exact training zone they desire. Human performance is going to keep getting better. There are many ways to skin a cat, but some are more efficient than others. I cannot argue with the results of the Zone 2 approach in cycling, but I am allowed to offer a counterfactual: what if McNulty, Pogacar, and company would be even better if they adopted the Norwegian approach? I think they would be. We know how well it works in distance running. So go buy a heart rate monitor, at least, and start doing double threshold and a lot of Zone 1!
Jamie
Puncheur 
Leave a comment