· Runima Team
Lactate Threshold: Your Hidden Redline
Your lactate threshold predicts race pace better than VO₂max. What LT1 and LT2 are, how to test them, and how to push your threshold higher.
Wait — what is lactate threshold?
First, kill the myth: lactate is not a waste product that "burns" your muscles. It's a fuel your body constantly produces and recycles. At easy efforts you clear it as fast as you make it, so blood levels stay flat. Push harder and production starts to outrun clearance — and where that balance tips defines your thresholds.
There are two, and confusing them is the single most common mistake runners make:
LT1 — the aerobic threshold
The pace where lactate first drifts above resting levels (around 2 mmol/L). Below it, you could run more or less all day. It's the ceiling of your truly easy running — and the floor you should keep most of your training under.
LT2 — the anaerobic threshold
The pace where lactate production sharply outpaces clearance and the curve turns vertical (often near 4 mmol/L). This is your redline: roughly the hardest effort you can hold for about an hour. When a watch or coach says "threshold," they mean this one.
Why does this matter more than VO2max? Because race pace lives at the threshold, not at the ceiling. In a database of 427 competitive runners, the speed at LT2 sat just a touch faster than half-marathon pace — exactly the effort that decides your long-distance results (Casado et al., 2023). The classic model of endurance performance has always listed three ingredients — VO2max, running economy, and lactate threshold (Bassett & Howley, 2000) — and for everything from the 5K up, threshold is the one that most directly sets the pace you can actually sustain.
How to find yours: testing LT1 and LT2
You can measure this — with anything from a sports-science lab to a free half-hour on a quiet road. Here's the honest trade-off between precision, cost, and hassle.
| Method | What it gives you | How good is it? | Cost & access |
|---|---|---|---|
| Lab graded test + blood lactate | LT1 and LT2 directly | Gold standard | $$$, lab visit |
| Multi-day MLSS test | LT2 (maximal lactate steady state) | The true reference, but laborious | $$$, several lab sessions |
| Lab gas analysis (ventilatory thresholds) | VT1/VT2 as proxies for LT1/LT2 | Very good — tracks lactate markers with ICC ≈0.82–0.90 | $$$, lab |
| Portable lactate analyzer | LT1 and LT2 (DIY) | Good if you follow a careful step protocol | $ (meter + strips), at home |
| 30-minute solo time trial | LT2 heart rate & pace | Solid practical proxy | Free |
| Critical-speed test (2–3 max efforts) | ≈ LT2 / sustainable ceiling | Good, math-based | Free |
| Talk test | Rough LT1 (can chat) vs LT2 (can't) | Low precision, surprisingly handy | Free |
| Smartwatch estimate | LT heart rate & pace | HR within ≈6–7% (±≈10 bpm); pace often over-estimated | Bundled with the watch |
A few notes on the practical options. The 30-minute time trial, popularised by coach Joe Friel, is the best free test: run all-out solo for 30 minutes and your average heart rate over the final 20 minutes approximates your LT2 heart rate, with that pace approximating threshold pace. It works because lactate-based threshold markers reliably predict steady-state and ventilatory thresholds (Cerezuela-Espejo et al., 2018).
Smartwatches (Garmin, COROS, Huawei and friends) will hand you a threshold number for free, but read it with care: across mainstream watches, lactate-threshold heart rate lands within about 6–7% of lab values (mean error roughly 9–11 bpm), while threshold pace is routinely over-estimated — by as much as ≈26% on some devices (smartwatch validation study, 2025). A systematic review reached the same verdict: useful for recreational runners and for tracking trends, shakier as an absolute number, especially for elites (Düking et al., 2025).
What sets your threshold — and what you can actually change
Threshold isn't one dial; it's the output of several. Some are largely handed to you by genetics; others move a lot with training. The number that matters for racing is threshold velocity (LTV) — the speed you hold at LT2 — and a study of 75 runners pinned down exactly what drives it (Støa et al., 2020):
| Factor | How much it matters | Trainable? |
|---|---|---|
| Maximal aerobic speed (VO2max ÷ economy) × LT% | Together explain ≈90% of threshold velocity | Yes — heavily |
| Threshold as a % of VO2max | Beginners ≈60%, trained ≈65–80%, elite ≈85–95% | Yes — via threshold work |
| Muscle fibre type / mitochondria / lactate transporters | Large; partly genetic, partly built by training | Partly |
| Sex (physiology) | Women average ≈2.5 points higher LT%, but ≈8% lower threshold speed and ≈21% lower VO2max, partly offset by better economy | Fixed |
| Training history & consistency | The biggest lever of all | Yes |
The headline is counter-intuitive: in that study, lactate threshold expressed as a percentage of VO2max didn't even correlate with how fast runners could actually go at threshold. What did? Aerobic speed and threshold together. The performance ladder is really a speed ladder — elite runners had ≈13% higher maximal aerobic speed than national-level runners, who had ≈24% higher than recreational runners. Translation: you raise threshold pace by improving VO2max, by improving economy, and by lifting the threshold itself — and they stack.
How to raise it
The core stimulus: threshold work
Tempo runs (20–40 minutes at "comfortably hard") and cruise intervals (say 4–5 × 8 minutes at threshold with short rests) are the most direct tool — they build the mitochondria, capillaries, and lactate-clearance machinery that push the curve rightward. And the dose matters: adding interval work once a week raised threshold by ≈4.3%, twice a week by ≈8.2% over six weeks (Kohn et al., 2011). Cranking the intensity higher in a structured block has moved threshold +11.7% alongside a ≈7% faster 3000 m (Smith et al., 2006).
The Norwegian way (scaled down)
The method behind the current crop of world-beating Norwegian distance runners is lactate-guided threshold training: large volumes of controlled work with blood lactate deliberately held around 2–4.5 mmol/L — often as two threshold sessions in a single day (Casado et al., 2023; Kelemen et al., 2023). You won't replicate elite volume, but the principle scales perfectly: two controlled threshold sessions a week, kept genuinely sub-maximal, surrounded by easy running.
Don't skip the easy miles
In a head-to-head of training models in well-trained athletes, a polarised distribution (mostly easy, some hard) produced the biggest endurance gains, while a threshold-only block produced the smallest (Stöggl & Sperlich, 2014). Threshold work is the sharp end; easy volume is what makes it stick and lifts LT1.
Whatever your starting line
The modality is negotiable; the principle isn't. Injured? Threshold intervals transfer beautifully to a bike or to deep-water running, which maintain lactate-clearance fitness with no pounding (cross-training research), and light-load blood-flow-restriction work keeps the supporting muscle while bone heals. No gym or budget? A hill or a quiet road is all a tempo run needs. Using a wheelchair or with a lower-limb disability? Upper-body and arm-crank training drive the same metabolic adaptations. The engine doesn't care what powers it — controlled, repeatable hard-but-not-too-hard work is what moves the threshold.
The pharmacy question: why "lactate" supplements don't raise your threshold
This is where most runners get fooled — so read carefully. The two famous "lactate" supplements do not raise your threshold at all. Sodium bicarbonate and beta-alanine are buffers: they help you tolerate the acidosis that builds when you're already working above threshold. Bicarbonate has a real but modest effect on short, hard efforts (pooled effect size ≈0.36–0.40 for ≈45 s–8 min bouts; umbrella review, 2021); beta-alanine nudges the onset of blood-lactate accumulation later (one running study shifted it from 69% to 76% of VO2max over 28 days; Jordan et al., 2010). Useful for your 5K and your intervals — useless for the sustainable pace itself.
Everything else you've heard about is even further off. Beetroot/nitrate trims the oxygen cost of running ≈3–5% in less-fit people (and fades as you get fitter); caffeine lowers how hard a pace feels (≈2–4% performance) without touching the threshold; iron only helps if you're genuinely deficient; and mega-dosing antioxidant vitamins C and E can actively blunt the adaptations your threshold work is trying to create.
Everything ranked: what actually moves your threshold
Approximate effect on threshold pace (the race-relevant number), biggest to none:
| Method | Approx. effect on threshold | What it's really doing | Evidence |
|---|---|---|---|
| ⚠️ Blood doping / EPO (banned — don't) | Large | Lifts O₂ delivery, VO2max, and threshold pace | Strong, but prohibited & unsafe |
| Threshold / tempo + cruise intervals | ≈+4–12% | Builds lactate-clearance machinery; moves the curve | Strong |
| More quality frequency (1→2 sessions/wk) | +4.3% → +8.2% | Dose-response on the threshold | Strong |
| VO2max intervals | Indirect, large | Raise aerobic speed → faster pace at threshold | Strong |
| Easy aerobic volume | Foundational | Lifts LT1, lets threshold work stick | Strong |
| Strength training | ≈0% on the curve | Improves economy ≈2–8% → faster threshold pace | Strong — indirect only |
| Heat acclimation | Small (+) | Expands plasma volume | Moderate |
| Altitude (live high–train low) | ≈0 to a few % (variable) | Raises red-cell mass; inconsistent payoff | Mixed |
| Sodium bicarbonate | ≈0% | Buffers efforts above threshold | Moderate — wrong target |
| Beta-alanine | ≈0% | Buffers 1–4 min efforts; delays OBLA slightly | Moderate — wrong target |
| Beetroot / nitrate | ≈0% in trained | Cuts O₂ cost ≈3–5% in less-fit (economy) | Moderate, fades with fitness |
| Caffeine | ≈0% | Lowers perceived effort (helps racing, not threshold) | Strong — wrong target |
| Iron | ≈0% (unless deficient) | Restores O₂ transport if depleted | Conditional |
| Creatine | ≈0% to slightly negative | Strength/power; adds water weight | Strong — not for endurance |
| High-dose antioxidants (C/E) | ≈0%, can be negative | May blunt training adaptations | Counterproductive |
| Herbals (cordyceps, etc.) | ≈0% | Marketing | Low / null |
"≈0%" means it does little or nothing to the threshold itself. Note the pattern: nearly every supplement is a buffer or a perception aid — it helps you survive efforts beyond your redline, but it doesn't move the redline. Only training does that. (And note strength work sits at ≈0% on the lactate curve yet still earns its place, because a better-economy runner hits any given lactate value at a faster pace — see Llanos-Lagos et al., 2024.)
The takeaway
VO2max is the engine. Lactate threshold is how much of that engine you can use, lap after lap, before the wheels come off — and for real races it's the better predictor of the two. The good news is that the most powerful lever is also the most boring: controlled threshold running, twice a week, on top of easy miles, measured honestly and nudged upward over months. No pill raises your redline. Your training does.
Test it. Track the trend. Then go raise it.
References
- Bassett DR, Howley ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc. 2000. https://pubmed.ncbi.nlm.nih.gov/10647532/
- Casado A, Foster C, Bakken M, Tjelta LI. Does lactate-guided threshold interval training within a high-volume low-intensity approach represent the "next step"? IJERPH. 2023. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10000870/
- Kelemen B, Benczenleitner O, Tóth L. The Norwegian double-threshold method in distance running: a systematic literature review. Sci J Sport Perform. 2023. https://sjsp.aearedo.es/index.php/sjsp/article/view/norwegian-double-threshold-method-distance-running
- Støa EM, et al. Factors influencing running velocity at lactate threshold in male and female runners at different levels of performance. Front Physiol. 2020. https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.585267/full
- Kohn TA, et al. Dose-response relationship between interval training frequency and magnitude of improvement in lactate threshold. Int J Sports Med. 2011. https://pubmed.ncbi.nlm.nih.gov/20535658/
- Smith TP, et al. Manipulating high-intensity interval training: effects on VO2max, the lactate threshold and 3000 m running performance. J Sci Med Sport. 2006. https://www.sciencedirect.com/science/article/abs/pii/S1440244006001149
- Stöggl T, Sperlich B. Polarized training has greater impact on key endurance variables than threshold, high-intensity, or high-volume training. Front Physiol. 2014. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3912323/
- Llanos-Lagos C, et al. The effect of strength training methods on middle- and long-distance runners' performance: a systematic review with meta-analysis. Sports Med. 2024. https://link.springer.com/article/10.1007/s40279-024-02018-z
- Cerezuela-Espejo V, et al. The relationship between lactate and ventilatory thresholds in runners: validity and reliability. Front Physiol. 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167480/
- Validity of smartwatch-derived estimates of lactate threshold heart rate and pace compared to graded exercise testing. Front Physiol. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12309276/
- Accuracy of wearables for determining maximal oxygen uptake and lactate threshold: a qualitative systematic review. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12748164/
- Sodium bicarbonate supplementation and exercise performance: an umbrella review. J Int Soc Sports Nutr. 2021. https://link.springer.com/article/10.1186/s12970-021-00469-7
- Jordan T, et al. Effect of beta-alanine supplementation on the onset of blood lactate accumulation during treadmill running. J Int Soc Sports Nutr. 2010. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2887393/
- The effects of dietary nitrate supplementation on endurance exercise performance: a systematic review and meta-analysis. 2021. https://www.tandfonline.com/doi/full/10.1186/s12970-021-00450-4
- Effects of caffeine intake on endurance running performance and time to exhaustion: a systematic review and meta-analysis. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC9824573/
- Effect of iron supplementation on exercise performance in women with iron deficiency: a systematic review and meta-analysis. 2025. https://www.sciencedirect.com/science/article/pii/S2773050625000655
- Paulsen G, et al. Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans. J Physiol. 2014. https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/jphysiol.2013.267419
- Cardiorespiratory and metabolic consequences of detraining in endurance athletes. Front Physiol. 2023. https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1334766/full
- Eyestone ED, et al. Effect of water running and cycling on maximum oxygen consumption and 2-mile run performance. Am J Sports Med. 1993. https://pubmed.ncbi.nlm.nih.gov/8427367/
- Low-load resistance training combined with blood flow restriction: a systematic review and meta-analysis. 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12129158/
This article is for general education and isn't medical advice. If you're injured or managing a health condition, clear new training with your clinician.
