Explainer, in Running
What Is Lactate Threshold? Meaning, Testing & Training
Lactate Threshold (LT) is the exercise intensity, typically measured as a heart rate or pace, at which the rate of lactate production in the muscles exceeds the rate of lactate clearance from the bloodstream, causing a rapid rise in blood lactate concentration.
4 questions. Published Mar 11, 2026. Updated Oct 19, 2026. By AI Fit Hub.
Definition
Lactate Threshold
Lactate Threshold (LT) is the exercise intensity, typically measured as a heart rate or pace, at which the rate of lactate production in the muscles exceeds the rate of lactate clearance from the bloodstream, causing a rapid rise in blood lactate concentration.
Why it matters
It is one of the three physiological factors, with VO2 max and efficiency, that determine endurance performance (Joyner & Coyle 2008), and lactate thresholds correlate strongly with race results, especially in running (Faude 2009). A higher threshold lets you hold a faster pace for longer, which is why it is a common target in half-marathon and marathon training.
How it works
Muscles produce lactate continuously, and more at higher intensities. The body clears it by using it as fuel in other muscle fibres and the heart, and by converting it back to glucose in the liver (the Cori cycle). Lactate threshold is the intensity at which production starts to outrun clearance. There is no single definition: Faude and colleagues found 25 different threshold concepts, ranging from the first rise above baseline to the maximal lactate steady state. Lab tests use a graded exercise test with blood samples. A common field estimate is a 30-minute solo time trial, taking the average heart rate of the last 20 minutes as lactate-threshold heart rate.
Example
Estimating Lactate Threshold Heart Rate (LTHR) for a runner using a 30-minute field test.
Warm-up duration
10 minutes easy run
Main effort duration
30 minutes maximal sustained effort
Average Heart Rate (first 10 min of main effort)
160 bpm
Average Heart Rate (last 20 min of main effort)
178 bpm
Cool-down duration
10 minutes easy run
Based on this 30-minute maximal effort test, this runner's estimated Lactate Threshold Heart Rate (LTHR) is 178 bpm. This is the heart rate they could theoretically sustain for a prolonged period without significant lactate accumulation, making it a critical metric for setting personalized training zones.
Key takeaways
Lactate Threshold marks the point where lactate production exceeds clearance, indicating the maximum sustainable intensity without rapid fatigue.
Improving your LT allows you to run faster for longer, directly enhancing endurance performance in races and sustained training efforts.
LTHR can be estimated through field tests (like a 30-minute maximal effort) and is used to define personalized, effective training zones.
Related terms
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Questions people ask next
How is Lactate Threshold measured?
The most accurate measurement of Lactate Threshold involves a graded exercise test in a lab setting. During this test, an athlete performs increasing intensities of exercise while blood samples are taken periodically to measure lactate levels. The point at which blood lactate concentrations begin to rise sharply, disproportionate to the increase in workload, is identified as the Lactate Threshold. Field tests, such as a 30-minute maximal effort run where the average heart rate of the last 20 minutes is taken, can also provide a practical estimation for training purposes.
What is the difference between Lactate Threshold and VO2 Max?
VO2 max is the most oxygen you can use; lactate threshold is the share of that maximum you can sustain. Joyner and Coyle describe endurance performance as the product of three factors: VO2 max and lactate threshold together set the oxygen uptake you can hold for a race, and efficiency turns that into speed or power. Two runners with the same VO2 max can race very differently if their thresholds differ.
Can Lactate Threshold be improved?
Yes. Lactate Threshold is highly trainable. Specific training methods, particularly tempo runs, threshold runs, and interval training, are designed to improve your body's ability to produce energy aerobically at higher intensities and clear lactate more efficiently. By consistently training near or slightly above your current LT, your body adapts by increasing mitochondrial density, improving enzyme activity, and enhancing lactate shuttle mechanisms, thereby pushing your Lactate Threshold to a higher intensity.
How do I use my Lactate Threshold in my running training?
Use it to set training zones. Once you have an estimate, from a lab test or a field test, set easy runs well below it, threshold or tempo runs at about that heart rate or pace, and intervals above it. Retest every couple of months, because the threshold moves as fitness changes, and remember that the 30-minute field test is an estimate rather than a lab measurement.
Sources
- Endurance exercise performance: the physiology of champions , The Journal of Physiology (2008) — Joyner & Coyle
- Lactate threshold concepts: how valid are they? , Sports Medicine (2009) — Faude, Kindermann & Meyer