Lactate Threshold: What It Is, Why It Matters & How to Test It

Lactate Threshold: What It Is, Why It Matters & How to Test It

Unlock a deeper understanding of your endurance performance potential.

Lactate threshold (LT) refers to the exercise intensity at which lactate begins to accumulate in the bloodstream faster than the body can clear it. While VO₂ max tells you how much oxygen you can use, lactate threshold tells you how long you can hold high intensities before fatigue kicks in. In endurance sports, that distinction makes all the difference.

When dialed in properly, LT helps athletes train smarter, race more efficiently, and unlock new levels of sustainable performance.

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WHAT IS LACTATE THRESHOLD?

Lactate is a byproduct of glucose metabolism and is naturally produced in your body during exercise. At low to moderate intensities, you’re able to clear lactate as quickly as it's produced, keeping blood levels relatively stable. But as intensity rises, you eventually hit a tipping point: the lactate threshold. Beyond this threshold, lactate begins to accumulate in the blood and your legs start to feel that familiar burn we all dread.

This point often occurs at 75–90% of an athlete’s VO₂ max, depending on training history and genetics. It's a key physiological marker because it closely reflects the maximum pace or power you can sustain for prolonged efforts (think 30–60 minutes for trained athletes).

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WHY LACTATE THRESHOLD MATTERS

1. Stronger Predictor of Performance Than VO₂ Max
   While VO₂ max defines your aerobic ceiling, lactate threshold defines how close to that ceiling you can operate. Two athletes may have identical VO₂ max values, but the one with the higher LT will typically outperform the other in endurance events.
2. It’s Highly Trainable
   Unlike VO₂ max, which has a strong genetic component, lactate threshold is highly responsive to training. Focused threshold sessions can lead to significant gains in sustainable power or pace within 8–12 weeks.
3. Essential for Zone-Based Training
   Identifying your LT allows for more accurate training zones, particularly Zone 3 and Zone 4, where small intensity shifts can mean the difference between aerobic conditioning and excessive fatigue.
4. Crucial for Race Pacing
   Whether you're racing a 10K, a triathlon, or a gran fondo, understanding your LT helps set realistic, performance-driven pacing strategies. You’ll know the intensity you can hold without “blowing up” late in the race.
5. ​​Reduces Injury Risk Through Smarter Pacing

Training at the right intensity is key to long-term durability. Knowing your pace or power at lactate threshold helps you avoid overreaching during workouts, which reduces unnecessary muscular breakdown, supports better recovery, and lowers your risk of injury over time.

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HOW LACTATE THRESHOLD IS TESTED

There are both laboratory-based and field-based methods for estimating your lactate threshold:

1. Lactate Testing in the Lab (Gold Standard)

• Conducted on a treadmill or cycle ergometer.
• Involves stepwise increases in intensity with finger-prick blood samples taken at each stage.
• The LT is identified by the point at which blood lactate begins rising exponentially.
• Best for precision and monitoring detailed progress over time.

2. Ventilatory Threshold via VO₂ Max Testing

• During a VO₂ max test, respiratory gas exchange is analyzed to find ventilatory thresholds (VT1 and VT2).
• VT2 closely approximates lactate threshold, offering a non-invasive estimate.
• Ideal for combining cardiorespiratory and metabolic insights in one session.

3. 30-Minute Field Time Trial (Heart Rate or Power-Based)

• Warm up thoroughly, then complete a solo 30-minute time trial at your best sustainable effort.
• Record average heart rate during the final 20 minutes—this approximates your Lactate Threshold Heart Rate (LTHR).
• For cyclists, the average power output is approximately your Functional Threshold Power (FTP).
• A practical, repeatable test for setting real-world training zones.

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EXAMPLE BLOOD LACTATE CURVE

In the chart above, we’re looking at blood lactate responses from two professional cyclists during an offseason step test. Both athletes have the same VO₂ max of 4.6 L/min, meaning they share the same aerobic ceiling. But the way their bodies handle rising workloads is very different.

Figure 1: Chart displaying two professional athlete’s blood lactate curves at increasing power output on a cycling ergometer [8].  

The key difference lies in where their lactate begins to accumulate rapidly. The point at which the blood lactate values begin to increase exponentially is considered the Lactate Threshold. Let’s take a look at both of these professional athletes' curves, and what this might mean from a performance perspective.

• Athlete 1 (black line) shows a clear inflection point in lactate accumulation around 235–250 watts.
• Athlete 2 (gray line) starts accumulating lactate markedly later, around 275–285 watts.

Despite having identical oxygen delivery potential (VO₂ max), Athlete 2 can sustain a higher power output before fatiguing. That higher threshold translates directly to better performance in long events, which means this athlete can ride harder for longer without hitting the wall.

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BRINGING IT ALL TOGETHER

Lactate threshold is one of the most powerful tools in an athlete’s physiology tool-kit. It’s trainable, trackable, and performance-relevant across all endurance disciplines. Whether you're aiming to fine-tune your race pace, build a smarter training plan, or gain objective insight into your fitness, lactate threshold testing provides meaningful data you can act on.

At SOVRN Performance Lab, our testing services, blood lactate and VO₂ max assessments, are designed to give athletes and coaches the physiological clarity they need to perform at their best.

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References

1. Brooks GA. The science and translation of lactate shuttle theory. Cell Metabolism. 2018;27(4):757–785. doi:10.1016/j.cmet.2018.03.008
2. Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they? Sports Med. 2009;39(6):469–490. doi:10.2165/00007256-200939060-00003
3. Midgley AW, McNaughton LR, Jones AM. Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge? Sports Med. 2007;37(10):857–880. doi:10.2165/00007256-200737100-00003
4. Billat LV. Use of blood lactate measurements for prediction of exercise performance and for control of training: recommendations for long-distance running. Sports Med. 1996;22(3):157–175. doi:10.2165/00007256-199622030-00004
5. Esteve-Lanao J, González-Mohíno F, Santos-Concejero J, Alcoba-Parra F. Polarized training has greater impact on key endurance variables than threshold, high-intensity, or high-volume training in trained endurance runners. Front Physiol. 2023;14:1164463. doi:10.3389/fphys.2023.1164463
6. Seiler S, Tønnessen E. Intervals, thresholds, and long slow distance: the role of intensity and duration in endurance training. Sportscience. 2009;13:32–53.
7. Coyle EF. Integration of the physiological factors determining endurance performance ability. Exerc Sport Sci Rev. 1995;23:25–63.
8. INSCYD. How to interpret a shift in lactate curves the right way. INSCYD website. https://inscyd.com/article/how-to-interpret-a-shift-in-lactate-curves-the-right-way/. Published March 2023. Accessed July 14, 2025.

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