Threshold training sparks endless debate among endurance athletes, CrossFitters, and fitness enthusiasts alike.
Yet most people misunderstand what “threshold” actually means from a physiological standpoint.
Gomar, a senior scientist at ETH Zurich who has spent the last decade studying exercise physiology, recently broke down the science of threshold training in a detailed video explanation.
His insights reveal why many athletes—especially in functional fitness—may be training at threshold intensity far too often, potentially hampering their long-term performance gains.
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What Threshold Actually Means
Forget the magic lactate number or specific heart rate zone.
Threshold represents a physiological tipping point where your body’s lactate production and clearance reach a delicate balance.
It’s the highest intensity that an athlete can sustain where lactate production from glycolysis and lactate clearance mostly from the muscles is in balance.
This concept, known as maximal lactate steady state (MLSS), describes the sweet spot where you’re working hard but not accumulating unmanageable fatigue.
During threshold work, lactate levels rise initially then plateau at a sustainable level—neither climbing into the red zone nor dropping as they would during easy Zone 2 training.
The Energy System Perspective
Understanding threshold becomes clearer when examining how your body produces energy across different intensities.
During walking or light jogging, aerobic pathways provide most of your energy with minimal contribution from glycolysis (the breakdown of glucose that produces lactate).
As intensity increases to threshold pace, you reach that critical balance: high aerobic energy production paired with significant—but still manageable—glycolytic activity.
Push beyond threshold into sprint territory, and glycolysis dominates. Byproducts accumulate rapidly, forcing you to slow down or stop.
According to Gomar, threshold also represents a local phenomenon within muscles themselves—the point where oxygen delivery to working muscles perfectly matches oxygen consumption.
How To Detect Your Threshold
Gomar presents threshold detection as a pyramid with three levels of complexity and accuracy.
The Gold Standard: Lactate Testing
The base of the pyramid—most accurate but most complicated—involves direct physiological measurement using lactate testing during a progressive exercise test.
Athletes perform a ramp test to exhaustion on a bike, treadmill, or rowing machine while lactate is measured from fingerstick blood samples at regular intervals.
Initially, lactate remains relatively flat as aerobic systems handle energy demands. Then comes the inflection point where lactate shoots upward exponentially.
That transition point marks your threshold.
Gomar tested an elite Hyrox racer and found his threshold at approximately 17.4 km/h—remarkably close to the pace he maintains during actual races.
I asked him okay what is the time that you usually do on a Hyrox like I mean not the time the speeds for running and then he said exactly 3 and a half minutes so three and a half to 3 minutes 40 which is exactly at his threshold speed 17 and 12 kilometers an hour.
For CrossFit athletes, Gomar developed a sport-specific protocol using thrusters and burpees in 4-minute intervals with 1-minute rest, measuring lactate throughout.
This approach provides threshold data relevant to functional movements rather than just running or cycling.
Muscle Oxygen Monitoring
Near-infrared spectroscopy (NIRS) devices offer another direct measurement approach by tracking oxygen saturation within working muscles.
These wearable sensors—from companies like Moxy and Train.Red—have dropped from €20,000 fifteen years ago to around €700 today.
During incremental exercise, muscle oxygen levels show breaking points where oxygen utilization outpaces delivery—closely corresponding to threshold.
NIRS provides a unique advantage: local muscle-specific threshold data that lactate testing can’t reveal.
When Gomar tested a rower preparing to cross the Atlantic, muscle oxygen data exposed a technique flaw invisible to systemic lactate measurement.
The athlete’s biceps deoxygenated far faster than his quadriceps, indicating he was pulling too aggressively with his arms rather than driving efficiently with his legs.
Several NIRS devices now include automated threshold detection algorithms, making the technology increasingly accessible for serious athletes.
Practical Derivatives: FTP and Heart Rate
The middle tier of Gomar’s pyramid uses derivatives—less accurate but far more practical for most athletes.
Functional Threshold Power (FTP) estimates threshold through a simple field test: complete a hard warm-up, rest 2 minutes, then sustain maximum effort for 20 minutes on a bike or rower.
Take 95% of your average power output, and you have an approximation of threshold power.
However, Gomar cautions that the 95% multiplier is just a ballpark figure.
CrossFit athletes with greater anaerobic capacity might need 90%, while pure cyclists could use 99%.
Heart rate zones offer another derivative approach, typically placing threshold at 88-93% of maximum heart rate.
Smartwatches from Garmin, Whoop, and others use algorithmic estimates based on population data—convenient but not individually precise.
The Simplest Method: Rate of Perceived Exertion
At the pyramid’s peak sits Rating of Perceived Exertion (RPE)—least accurate but easiest to implement.
Threshold work typically feels like 6-7 out of 10: hard and somewhat uncomfortable, but sustainable.
One challenge: functional fitness athletes often struggle to calibrate their RPE accurately.
Years of high-intensity training can skew perception—some athletes rate brutal workouts as “moderate” while others catastrophize moderate efforts.
Gomar recommends performing the thruster-burpee lactate test while recording RPE after each interval to establish personal reference points across the intensity spectrum.
The Jakob Ingebrigtsen Case Study
Norwegian middle-distance phenom Jakob Ingebrigtsen dominated the 1,500m and 5,000m from 2020 onward, running 1,500m in a blistering 3:30.
A 2019 paper examining his training approach revealed something fascinating about threshold work.
Ingebrigtsen logged massive weekly volume—140-160 kilometers—but meticulously monitored his threshold sessions using lactate measurements.
He didn’t rely on pre-calculated paces or generic formulas. Instead, he tested lactate during threshold workouts to ensure he stayed at threshold without exceeding it.
Why such precision?
Because pushing even slightly above threshold triggers rapid fatigue accumulation and compromises recovery—critical considerations for high-volume training blocks.
This principle extends beyond endurance sports into CrossFit and Hyrox, where recovery between sessions determines sustainable progress.
Why Threshold-Only Training Doesn’t Work
If threshold training pushes your aerobic system hard while remaining recoverable, why not do it exclusively?
Research provides a definitive answer.
A well-designed study tracked 48 highly trained cyclists, triathletes, and runners (all with VO2max above 62 ml/kg/min) through nine weeks of different training approaches:
- Polarized training: Mix of low-intensity and high-intensity work with minimal threshold
- High-intensity interval training (HIIT): Predominantly hard efforts
- Threshold training: Consistent work at threshold pace
- High-volume training: Large amounts of low-intensity work
The results were striking.
Polarized training produced a 10% VO2max improvement—by far the best outcome. HIIT delivered a respectable 5% gain.
But threshold-only training actually decreased VO2max.
The research here is more nuanced than a single study might suggest. A 2014 systematic review in Sports Medicine found that while threshold training improves lactate threshold and time-trial performance, it produces smaller gains in maximal aerobic capacity compared to polarized or HIIT approaches. The review noted that threshold training’s primary benefit lies in improving sustainable pace rather than expanding the cardiovascular ceiling—making intensity variation essential for well-rounded development.
This finding carries massive implications for functional fitness athletes.
The CrossFit Threshold Trap
Gomar identifies a common pattern in CrossFit gyms: athletes show up 5 times per week, work on strength, then tackle an 8-20 minute AMRAP or for-time workout.
The typical approach? Start fast, settle into a threshold-ish pace, then sprint through the final round.
In my opinion that is potentially harming your long-term development because as we saw from that last study and also other studies it’s not necessarily the best way to improve your cardiovascular capacity.
This creates an accidental threshold overload—too much time in that middle-intensity zone without the polarizing contrast of truly easy aerobic work or genuinely maximal efforts.
The fatigue accumulates, recovery suffers, and cardiovascular adaptation stalls despite consistent hard work.
Elite endurance athletes have known this for decades: they combine abundant Zone 2 volume with targeted high-intensity sessions, using threshold work strategically rather than defaulting to it constantly.
How To Program Threshold Training Intelligently
The solution isn’t eliminating threshold work—it’s varying intensity deliberately throughout your training week.
Gomar suggests a sample CrossFit week that illustrates this principle:
- Monday: Sprint intervals
- Tuesday: 15-minute AMRAP (threshold-ish)
- Wednesday: Rest
- Thursday: Dedicated threshold work
- Friday: 5 rounds for time (varied intensity)
- Saturday: Rest
- Sunday: Zone 2 aerobic session
This structure creates genuine intensity variation rather than grinding through moderately-hard workouts daily.
It allows progressive overload without constant fatigue while preserving time for skill development and movement efficiency—both crucial in functional fitness.
A Double Threshold Day Example
For Hyrox athletes or those pursuing advanced conditioning, Gomar proposes a “double threshold” training day:
Morning session: 4 x 7 minutes on the rower or running at your tested threshold pace with appropriate rest.
Afternoon session: Functional threshold EMOM—every minute for 40 minutes, complete 20m sled push, 15 pull-ups, 17 wall balls, then rest until the next minute.
The critical instruction: hold a sustainable RPE 6-7 pace.
For most athletes, this feels slower than their instinctive training intensity—and that’s precisely the point.
True threshold work requires discipline to stay at the tipping point rather than constantly pushing beyond it.
Key Takeaways For Your Training
Threshold isn’t a single number but a physiological tipping point where lactate production and clearance balance.
You can measure it precisely using lactate testing or muscle oxygen sensors, estimate it through FTP or heart rate derivatives, or gauge it via RPE.
Threshold training offers unique benefits: it pushes your aerobic system hard while generating manageable fatigue, supporting consistent training without excessive recovery demands.
However, threshold-only programming proves counterproductive. Research demonstrates that polarized training—combining low-intensity volume with high-intensity work—outperforms constant threshold grinding for improving cardiovascular capacity.
Many functional fitness athletes inadvertently spend too much time near threshold through repeated AMRAPs and moderately-paced MetCons.
This creates high fatigue without optimal adaptation.
The solution: deliberate intensity variation. Program true Zone 2 sessions, genuine threshold work, and legitimately hard intervals rather than defaulting to “pretty hard” every training day.
Use threshold training strategically—as one tool among many—rather than the default setting for every conditioning piece.
Your long-term performance development depends on this diversity of training stress far more than accumulating additional threshold volume.
Sources
- Stöggl T, Sperlich B. Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Front Physiol. 2014;5:33. https://doi.org/10.3389/fphys.2014.00033
- Tønnessen E, Svendsen IS, Rønnestad BR, Hisdal J, Haugen TA, Seiler S. The annual training periodization of 8 World Champions in orienteering. Int J Sports Physiol Perform. 2015;10(1):29-38. https://doi.org/10.1123/ijspp.2014-0005
- Seiler S, Tønnessen E. Intervals, thresholds, and long slow distance: the role of intensity and duration in endurance training. Sportscience. 2009;13:32-53. http://www.sportsci.org/2009/ss.htm
- Buchheit M, Laursen PB. High-intensity interval training, solutions to the programming puzzle: Part I: cardiopulmonary emphasis. Sports Med. 2013;43(5):313-338. https://doi.org/10.1007/s40279-013-0029-x
- Gibala MJ, Little JP, Macdonald MJ, Hawley JA. Physiological adaptations to low-volume, high-intensity interval training in health and disease. J Physiol. 2012;590(5):1077-1084. https://doi.org/10.1113/jphysiol.2011.224725
