The Science Behind the Norwegian Method of Endurance Training

If you are into endurance training, you have probably heard something about the Norwegian method. So, what is that?

Norwegian training methodology is an endurance training theory that has been booming over the past half a decade. Mostly because it keeps delivering results. From Jakob Ingebrigtsen on the track to Kristian Blummenfelt and Gustav Iden crushing Ironmans, it’s proof that training smart around your lactate threshold really works.

On TriWorldHub, we are into all things training and science. So, we wanted to explore this method from the inside out. That’s the first article in our Norwegian training series, and it dives into the science behind the Norwegian method and what it means in practice. Let’s see why this training method is changing how endurance athletes train around the world.

What is Norwegian Training Method?

We’ll start with the basics: what does the Norwegian method mean, and what makes this style of training so unique?

At its core, the Norwegian method is a high-volume, low-intensity training approach where intensity is carefully controlled through lactate threshold testing. Instead of relying on feel or heart rate alone, athletes measure blood lactate levels during workouts to see if they’re training right at their individual lactate threshold, which is typically around 2–3 mmol/L.

In its purest form, the method often includes “double threshold” days, meaning two workouts in one day at threshold intensity. These are hard enough to stimulate adaptation, but controlled enough to avoid overtraining.

Brad Culp, author of the book called The Norwegian Method, describes it as more than just a training schedule. He sees it as a holistic system, one that starts from how young Norwegian athletes are raised with a huge attention to consistency, patience, and scientific feedback. It’s more than just piling on volume. The approach is focused on building an entire lifestyle that supports elite endurance performance.

What makes the Norwegian method truly unique is this combination of precision and patience, says Brad. While many traditional programs push athletes toward polarized models (lots of easy training with occasional all-out efforts), the Norwegian method focuses on sustained, repeatable threshold sessions that maximize aerobic development without excessive fatigue.

And it’s hard to argue with results. Jakob Ingebrigtsen has dominated the track in the 1500 m and 5000 m, while Kristian Blummenfelt and Gustav Iden have rewritten triathlon history. Their success has turned Norway’s endurance system into a global benchmark for smart, data-backed training.

A Brief History of Norwegian Training Method: How It Started

The roots of the Norwegian method go back to the late 1990s, when Olympiatoppen (OLT), Norway’s elite sports performance center, was actively collaborating with coaches and athletes across several sports (skiing, running, triathlon, etc.) to refine endurance training principles.

Marius Bakken, one of Norway’s top 5,000 m runners at the time, worked directly with OLT physiologists such as Espen Tønnessen and Frank Evertsen, using lactate testing to fine-tune his own training. In his article called Norwegian Method, Bakken describes how it all happened:

We tested various threshold formats, guided by Frank’s expertise. He also introduced me to the concept of muscle tone, via his colleague Johnny Høgseth, which became a vital factor in managing training load.

Lastly, he introduced me to altitude training, leading to my first trip to Kenya in 2000. That allowed for even higher threshold development and gave us the chance to observe and cross-test Kenyan training intensities firsthand, as referred to above.

We even experimented with extreme days—up to four-five sessions in a single day—mixing threshold and sprint components.

Marius shares how his typical training day looked like:

• Monday: 8 x 1000m at 5–8 mmol lactate
• Mid-week: Long threshold on Wednesday or Thursday, or both days.
• Saturday: Shorter, faster efforts (e.g. 200m intervals) often combined with threshold in the evening
• Sunday: A single run, never exceeding one hour

Later, Marius mentions, he has changed his training and made it more data-driven. After 2002, he implemented the key changes to his own training program:

• He removed the 5–8 mmol 1000m sessions in the winter entirely
• Reduced volume in single threshold sessions, but doubled up with systematic double threshold training several times weekly over long periods of time
• Adjusted the lactate levels slightly down from previous levels

By winter 2004, everything clicked. Reviewing my training log/diary from that time, it was the first time I followed what would later be recognized as the typical Norwegian model week during the base period, session by session

This is what his upgraded training program looked like from February 2004:

• Monday: 2 easy runs, zone 1
• Tuesday AM: Long intervals (6 x 2000m, lactate 2–3 mmol)
• Tuesday PM: 20–25 x 400m (lactate close to 3.0)
• Wednesday: 2 easy runs, zone 1
• Thursday AM: 4 x 10 min intervals (lactate 2–3 mmol)
• Thursday PM: 10–12 x 1000m intervals (lactate near 3.0)
• Friday: 2 easy runs, zone 1
• Saturday AM:  10 x 200 meters 26-28.
• Sunday: Long run, never longer than 16–18 km

At the time, this training model wasn’t a unified national training philosophy. Different groups followed different influences, from Arthur Lydiard’s high-mileage aerobic base training to the Sebastian Coe–inspired higher-intensity, interval-heavy approaches.

What made the Norwegian approach stand out was its scientific rigor. Instead of relying on intuition or generalized “zones,” the coaches used frequent lactate testing (both in training and in controlled sessions) to check if the athletes trained right below or at their maximal lactate steady state (MLSS).

This shift was controversial. Many coaches argued that threshold work wasn’t “specific” enough and that training at or near race pace was essential for peak performance. But over time, the measurable improvements in endurance and consistency among Norwegian athletes began to turn heads — laying the foundation for what we now call the Norwegian Method.

Maximal Lactate Steady State (MLSS)

This is the scientific backbone of the Norwegian method.

MLSS is the highest exercise intensity you can sustain, where lactate production and clearance are balanced.

In other words, it’s the point where your body works as hard as possible without tipping over into unsustainable fatigue. For most elite athletes, that sweet spot sits around 2–3 mmol/L of blood lactate.

Training repeatedly at or just below MLSS improves two crucial systems: your aerobic capacity and your ability to process lactate efficiently. Over time, this pushes the threshold higher, meaning you can hold faster paces for longer.

What makes the Norwegian approach unique isn’t the concept itself, it’s how precisely they control it. Athletes like Jakob Ingebrigtsen and Kristian Blummenfelt don’t rely on “feel” or heart-rate zones alone. They measure blood lactate after nearly every key session to confirm they’re right on target.

This data-driven discipline lets them accumulate huge volumes of quality work right below the red line, where the biggest aerobic gains happen without overtraining.

Scientific studies back up this philosophy.

• Faude, Kindermann & Meyer (2009, Sports Medicine) reviewed decades of research and confirmed that MLSS is one of the most accurate predictors of endurance performance — often even more reliable than VO₂ max. They concluded that training at MLSS defines the upper limit of sustainable aerobic metabolism.

• Beneke & von Duvillard (1996, Medicine & Science in Sports & Exercise) established standardized protocols for determining MLSS, proving it to be a reproducible and valid measure of an athlete’s highest sustainable workload.

What is the Lactate Threshold?

For decades, lactate (often mistakenly called lactic acid) was viewed as the enemy of the athlete. A waste product that causes muscle fatigue and burning.

Modern science has completely overturned this view. We now understand lactate as a crucial energy currency. It is produced continuously in the muscles, even at rest, and its concentration in the blood becomes a powerful biomarker for exercise intensity control.

The relationship between exercise intensity and blood lactate concentration follows a predictable curve with two critical inflection points:

1. Lactate Threshold 1 (LT1): The first sustained rise in blood lactate above baseline (~2 mmol/L). Below this intensity, lactate clearance matches production. This represents the upper boundary of “easy” training, the pace sustainable for marathons or ultra-endurance events. Training here improves aerobic efficiency and fat metabolism.
2. Lactate Threshold 2 (LT2): The second lactate threshold is the point where lactate begins accumulating rapidly (~4 mmol/L for many athletes). Above this intensity, fatigue arrives within minutes. This threshold is closely related to, but not identical to, MLSS.
3. Maximal Lactate Steady State (MLSS): The highest intensity at which lactate remains stable over time. MLSS typically sits slightly below LT2 and must be determined through repeated testing at different intensities. For elite athletes, this often corresponds to blood lactate concentrations of 2-4 mmol/L, though individual variation is substantial.

The logic is simple: if you can precisely stay under the red line, you can safely repeat the effort and build enormous aerobic capacity over time. Their attention to recovery, fueling, and monitoring makes this possible.

This approach adheres to one of the core principles of exercise physiology: specificity. To improve the systems that determine your performance at MLSS, you must train those systems often and specifically.

Visually, this relationship is shown by the lactate-power curve. When that curve shifts to the right, meaning you can produce more power or speed at the same lactate level, it signals a major endurance breakthrough. The Norwegian method is designed precisely to cause that shift through structured, threshold-focused training.

High-Frequency, High-Volume Stimulus at MLSS

The Norwegians’ biggest innovation isn’t that they discovered threshold training, it’s how often and precisely they do it.

While most endurance programs include one threshold or tempo workout per week, Norwegian athletes often perform two controlled threshold sessions per day, sometimes several days a week. Each session is guided by real-time lactate testing to check if the blood lactate stays steady around 2–3 mmol/L.

The Practical Protocol

A typical Norwegian threshold session might look like:

• Warm-up: 15-20 minutes easy
• Main set: 4-6 × 8-10 minutes at target pace
  • Lactate tested after each interval (target: 2-4 mmol/L, stable across intervals)
  • 2-3 minutes easy recovery between intervals
• Cool-down: 10-15 minutes easy

Crucially, if lactate readings drift too high (>4-5 mmol/L) or continue rising, the session is adjusted or terminated. The goal is stimulus accumulation, not exhaustion.

Important Context: This Isn’t Daily

During base and maintenance phases, Norwegian athletes follow more conventional patterns (1-2 threshold sessions per week). The high-frequency approach (4-6 sessions weekly, sometimes with doubles) is reserved for specific preparation phases lasting 3-8 weeks before major competitions. This periodization prevents overtraining while maximizing race-specific adaptations.

Between hard weeks, recovery weeks with reduced volume and intensity allow for physiological adaptation and prevent accumulated fatigue.

What Happens Inside the Body

Training repeatedly at MLSS triggers powerful physiological adaptations:

1. Mitochondrial Biogenesis

Holloszy (1967) first demonstrated that endurance training dramatically increases both mitochondrial quantity and efficiency. MLSS work activates key molecular signaling pathways (notably AMPK and PGC-1α) that stimulate mitochondrial growth, enhancing the muscles’ capacity for aerobic energy production.

The intensity matters: MLSS provides sufficient training stimulus to trigger adaptation without the inflammatory stress and extended recovery demands of supra-maximal work.

2. Enhanced Lactate Shuttling and Oxidation

Brooks (2018) demonstrated that lactate isn’t merely a metabolic byproduct, it’s a preferred fuel source. Regular MLSS training enhances:

• Monocarboxylate transporters (MCTs) that shuttle lactate between cells
• The capacity of Type I (slow-twitch) muscle fibers to oxidize lactate as fuel
• The ability to clear lactate from working muscles to the heart, liver, and kidneys

This “lactate shuttle” efficiency allows athletes to sustain higher intensities longer, as the body becomes adept at recycling what was once considered waste into usable energy.

3. Increased Capillarization

Consistent threshold training stimulates angiogenesis, the formation of new capillaries around muscle fibers. More capillaries mean:

• Improved oxygen delivery to working muscles
• Enhanced nutrient supply during exercise
• More efficient removal of metabolic byproducts
• Better thermoregulation

4. Cardiac Adaptations

While not always emphasized, MLSS training drives significant cardiovascular changes:

• Increased stroke volume (blood pumped per heartbeat)
• Enhanced cardiac output at submaximal intensities
• Improved oxygen extraction at the muscle level (a-vO₂ difference)

5. Fiber Type Optimization

MLSS work recruits predominantly Type I fibers with some Type IIa contribution. This specific recruitment pattern:

• Enhances the oxidative capacity of Type IIa fibers
• Improves the endurance characteristics of fast-twitch muscles
• Optimizes the transition between fiber types during sustained efforts

The Goal: Rightward Shift of the Lactate Curve

When training works, the entire lactate-power curve shifts right. This means an athlete produces less lactate (or the same lactate at higher speeds), signaling improved aerobic capacity, better lactate clearance, and enhanced endurance performance. The Norwegian Method is designed precisely to cause this shift through structured, precisely controlled lactate threshold training.

Comparing the Norwegian Method vs. Traditional Interval Models

While most elite training programs share common elements, they differ significantly in how they balance easy, moderate, and high-intensity work.

The Three-Zone Model: A Framework for Comparison

To compare training methods, we’ll use a simplified three-zone intensity model based on lactate thresholds:

• Zone 1 (Low intensity): Below the first lactate threshold (LT1), typically <2 mmol/L blood lactate. Conversational pace, sustainable for hours. Builds aerobic base and promotes recovery.
• Zone 2 (Moderate/Threshold intensity): Between LT1 and LT2, typically 2-4 mmol/L blood lactate. This is “threshold” or “tempo” training,comfortably hard, sustainable for 30-90 minutes. Targets lactate clearance and aerobic power.
• Zone 3 (High intensity): Above LT2, typically >4 mmol/L blood lactate. Hard intervals at VO₂max or higher. Sustainable for only a few minutes per interval. Maximizes cardiovascular capacity and neuromuscular power.

The Polarized Training Distribution (“The 80/20 Rule”)

Under the polarized training model, often called the 80/20 rule, around 80% of all training is done at low intensity. These are easy, conversational pace workouts below the first lactate threshold (LT1).

The remaining 20% is high-intensity training, close to the athlete’s limits. Very little training happens in the middle zone, sometimes called the “gray zone,” because it’s too hard to fully recover from but not hard enough to create big improvements.

This approach was first described in detail by Seiler and Tønnessen (2009) in their review “Intervals, thresholds, and long slow distance: the role of intensity and duration in endurance training.” They analyzed the training logs of elite runners, rowers, and cross-country skiers.

Across all sports, the same pattern appeared: most successful athletes spent about four-fifths of their time training easily, and only one-fifth pushing hard. Their workouts followed a clear two-peak (bimodal) pattern: lots of easy training and a smaller portion of high-intensity work, with very little time spent in between. This combination helped professional athletes adapt better and avoid burnout.

Later, Stöggl and Sperlich (2014) tested this idea in a 9-week controlled study. They compared athletes using different intensity distributions, polarized (80/20), threshold-focused, high-intensity, and high-volume approaches. The polarized group showed the largest improvements in VO₂max, power at VO₂max, and time to exhaustion.

The results were clear: the polarized group made the biggest gains in VO₂ max, power at VO₂ max, and time to exhaustion. In other words, they became fitter, stronger, and more resistant to fatigue than the other groups.

Strengths:

• High total training volume possible due to adequate recovery
• Proven effective across multiple endurance sports
• Clear intensity guidelines reduce guesswork

Limitations:

• Limited time spent at race-specific intensities for middle-distance events
• May not optimize lactate clearance capacity
• Less frequent exposure to sustained threshold efforts

Pyramidal Intensity Distribution

Under the pyramidal intensity distribution training model, most training remains in the low-intensity zone, but significant time is dedicated to threshold work, with less emphasis on maximal intervals. The distribution resembles a pyramid: a wide base of easy work, a substantial middle layer of threshold training, and a small peak of high-intensity work.

This shift isn’t random. Research by Haugen et al. (2022) on world-class distance runners and triathletes shows that the most successful programs tend to combine large low-intensity volumes with frequent, moderate-intensity sessions rather than relying heavily on maximal intervals.

“A pyramidal training intensity distribution, with a high proportion of threshold training, appears to characterize many world-class endurance athletes.”
— Haugen et al., 2022, Sports Medicine

However, the authors emphasized significant individual variation and cautioned against declaring any single distribution as universally optimal.

Strengths:

• Substantial threshold training improves race-specific fitness
• More time at “comfortably hard” paces
• May better prepare athletes for sustained threshold efforts in competition

Limitations:

• More difficult to recover from compared to the polarized approach
• Requires careful monitoring to avoid accumulating fatigue
• Higher injury risk if Zone 2 volume exceeds recovery capacity

Threshold-Heavy Model (Traditional Tempo Focus)

The threshold-heavy model focuses a lot of training around the “comfortably hard” zone, not easy, but not all-out either. Athletes spend most of their time near race pace, especially in Zone 2, with less truly easy training. This helps build strength and mental toughness for long, steady efforts like marathons or triathlons.

But it also causes fatigue to build up quickly, limits how much total training you can handle, and increases the risk of overtraining or injury. That’s why it often works for short periods but is hard to sustain long-term, especially for non-elite athletes.

Intensity distribution:

• 60-65% Zone 1 (easy)
• 30-35% Zone 2 (threshold/moderate)
• 5-10% Zone 3 (high intensity)

Heavy emphasis on tempo and threshold work with reduced easy volume. Common in marathon training programs and some triathlon approaches.

Strengths:

• Extensive race-pace training for threshold events
• Develops mental toughness for sustained hard efforts

Limitations:

• High fatigue accumulation
• Reduced total training volume capacity
• Elevated injury risk
• Often leads to overtraining in non-elite athletes

The Norwegian Method: A Modified Threshold-Pyramidal Approach

The Norwegian method doesn’t fit neatly into traditional classifications. It is sort of a data-driven evolution that combines elements of both polarized and pyramidal approaches, executed with exceptional precision. Here is what I mean by that:

Intensity Distribution

Based on analysis of Norwegian elite athletes’ training sessions (including the Ingebrigtsen brothers, Kristian Blummenfelt, and Gustav Iden):

• 70-75% Zone 1 (easy, conversational pace)
• 20-25% Zone 2 (threshold work, precisely controlled via lactate testing)
• 3-5% Zone 3 (high-intensity intervals, used sparingly)

The key differences include:

1. Precision Through Lactate Testing

Unlike traditional threshold training based on pace, heart rate, or perceived effort, Norwegian athletes measure blood lactate during and after nearly every threshold session to check if they’re working at true MLSS (typically 2-4 mmol/L, individually determined) rather than guessing.

Practical example:

• Traditional threshold workout: “Run 6 × 1 mile at 10K pace minus 10 seconds”
• Norwegian threshold workout: “Run 6 × 6 minutes, testing lactate after each interval; adjust pace to maintain 2.5-3.5 mmol/L”

This precision allows for higher training frequency because athletes consistently hit the target intensity without overshooting into excessive fatigue.

2. High-Frequency Threshold Training

During peak training blocks (typically 3-8 weeks before major competitions), Norwegian athletes may perform:

• 4-6 threshold interval sessions per week (compared to 1-2 in polarized models)
• Occasional double-threshold days: Two threshold sessions in one day, separated by 6-8 hours

Critical context: This high frequency is periodized, not year-round. During base phases and recovery weeks, frequency drops to 2-3 threshold sessions weekly, similar to conventional approaches.

Example double-threshold day:

• Morning: 6 × 6 minutes at 2.5-3.0 mmol/L (moderate threshold)
• Evening: 8 × 4 minutes at 3.0-3.5 mmol/L (upper threshold)
• Lactate measured after intervals in both sessions
• If lactate rises above target or recovery metrics indicate excessive stress, the session is modified or cancelled

3. Shorter Intervals with Brief Recovery

Rather than long continuous threshold efforts (20-40 minutes), Norwegian sessions often use:

• Shorter intervals (4-10 minutes)
• Brief recoveries (1-3 minutes easy jogging)
• More repetitions (6-12 intervals per session)

This structure allows athletes to accumulate more total time at threshold pace while managing fatigue within each session.

Shorter intervals with brief recovery enable athletes to maintain consistent lactate levels across the entire session, whereas continuous threshold runs often see lactate drift upward, making the latter portion much harder and requiring longer recovery.

Billat et al. (2000) demonstrated that interval training at the velocity associated with VO₂max allows athletes to accumulate more time at high intensities compared to continuous efforts, with better lactate control.

4. Minimal True VO₂max Work

Unlike polarized models that emphasize 3-5 minute intervals at 95-100% VO₂max, Norwegian athletes perform very little work at maximal intensities during most training phases. When they do include VO₂max sessions, they’re highly specific and limited to pre-competition periods.

Why This Works: The Physiological Rationale

The Norwegian approach exploits a key principle of exercise physiology: training just below the accumulation point allows for maximum stimulus with minimal recovery cost.

Simply put, the Norwegians train right below the point where fatigue starts to build up too quickly. At that level, the body gets a strong training effect, you’re working hard enough to improve, but not so hard that you need several days to recover.

When athletes train precisely at MLSS:

1. Lactate production and clearance remain balanced, preventing the metabolic acidosis that causes rapid fatigue
2. Mitochondrial signaling pathways (AMPK, PGC-1α) are activated without excessive inflammatory stress
3. Training can be repeated frequently because recovery demands are lower than supra-threshold work
4. Total weekly threshold volume can be 2-3 times higher than in polarized models

A study by Faude and colleagues in 2009 looked at trained runners doing a 40-minute run at their threshold pace. The runners who kept their blood lactate levels around 2–3 mmol/L were working hard, about 79% of their maximum oxygen use (VO₂max) and 92% of their max heart rate. That’s a tough but sustainable effort they could repeat regularly.

The researchers also noticed that every athlete’s numbers were a bit different, which shows that threshold training should be personalized. What counts as the right intensity for one person might be too easy or too hard for someone else.

Studies on threshold training adaptations show consistent results:

• Esfarjani & Laursen (2007): Seven weeks of threshold-style intervals improved lactate threshold by 19-22% and VO₂max by 5-6% in trained athletes
• Jones & Carter (2000): Meta-analysis of 85 study groups found trained athletes consistently improved lactate threshold with an effect size of ~0.63, making it one of the most reliable markers of endurance progress

Norwegian Double Threshold Training Strategy

The Norwegian innovation is the strategic use of double threshold days to accumulate extraordinary volumes of quality work.

Two moderate threshold sessions (6-8 out of 10 intensity) produce greater total adaptation stimulus than one exhausting VO₂max session (9-10 out of 10 intensity), while requiring less recovery time.

Key elements of their training strategy:

• 4 threshold sessions across 4 days
• Total threshold time: ~60-75 minutes per week
• Easy days remain truly easy (below LT1)
• One long aerobic session for base maintenance (for example, a long distance running training)
• Lactate testing at every threshold session

This structure is maintained for 3-6 weeks, then followed by a recovery week with reduced volume and only 1-2 threshold sessions.

Conclusion: What Makes the Norwegian Method Endurance Training Special

Here’s what I find most exciting about the Norwegian Method: it’s not trying to reinvent endurance training or claim that everything we knew before was wrong. Instead, it takes what already works and makes it more precise.

Think of it this way: polarized and pyramidal training have helped athletes succeed for decades. The Norwegians simply asked, “What if we could hit our targets more accurately and train more consistently without breaking down?” The answer came through four key innovations:

• Using lactate testing to nail the right intensity every time (no more guessing)
• Training at threshold more frequently during key preparation phases (when it really matters)
• Staying conservative enough that you can actually recover and repeat the work
• Letting data guide decisions instead of relying solely on how you feel

Now, should you rush out and incorporate a lactate-controlled approach and buy a lactate meter tomorrow? Maybe, maybe not. If you’re competing seriously at middle distances and have the resources, it could be a game-changer. But even if lactate testing isn’t in your budget, there’s real value in understanding these principles. You can apply the same logic: controlled intensity, higher frequency when appropriate, careful recovery monitoring, to make your threshold training more effective.

The biggest takeaway for me is this: good threshold training doesn’t have to leave you wrecked. It’s not about how much you can suffer in a single session. It’s about finding that sweet spot where you can work hard enough to improve, but sustainably enough that you can come back and do it again. And again. That’s where the real progress happens, in the accumulation of well-executed work over time, not in isolated heroic efforts that leave you toast for a week.