Key takeaways

• Lactate threshold is a critical determinant of endurance performance
• It is best understood as two points: LT1 (aerobic threshold) and LT2 (anaerobic threshold)
• Raising lactate threshold allows athletes to sustain higher intensities for longer
• Threshold training must be carefully structured to avoid excessive fatigue
• Lactate testing and well-defined training zones improve training precision

Introduction

When endurance athletes talk about getting fitter, faster, or more efficient, lactate threshold is often at the centre of the discussion. It represents the exercise intensity at which sustainable effort begins to give way to rapid fatigue. Improving lactate threshold allows athletes to run faster, cycle harder, or row stronger without accumulating excessive fatigue.

Understanding lactate threshold helps athletes train smarter. Rather than guessing intensity, it provides a physiological framework for structuring training, pacing efforts, and managing fatigue across a season.

What is lactate threshold?

Lactate threshold refers to the exercise intensity at which lactate begins to accumulate in the bloodstream faster than it can be cleared. In modern endurance physiology, this is not viewed as a single point, but as two distinct thresholds known as LT1 and LT2.

LT1, often referred to as the aerobic threshold, is the first sustained rise in blood lactate above resting levels. Below LT1, energy production is predominantly aerobic and highly sustainable. This intensity can typically be maintained for long durations and forms the foundation of endurance training.

LT2, commonly called the anaerobic threshold or maximal lactate steady state, represents the highest intensity that can be sustained without continual lactate accumulation. Above LT2, fatigue increases rapidly and exercise duration becomes limited. LT2 is closely associated with race pace in endurance events lasting from several minutes to over an hour.

Why lactate threshold matters for performance

Lactate threshold is one of the strongest predictors of endurance performance. Athletes with a higher LT2 can sustain faster speeds or higher power outputs while remaining metabolically stable. This often matters more than maximal oxygen uptake alone.

LT1 is equally important. Spending sufficient training time below LT1 improves mitochondrial density, fat oxidation, and aerobic efficiency. Together, LT1 and LT2 define effective training zones and guide how intensity should be distributed across the week.

Lactate production and fatigue

Lactate production is a normal consequence of energy metabolism during exercise. As intensity increases, the rate of glycolysis rises and lactate production increases. Lactate itself is not a waste product. It can be used as a fuel source by working muscles and other tissues.

Fatigue associated with high-intensity exercise is primarily linked to the accumulation of hydrogen ions that accompany lactate production, which disrupt muscle contraction and energy production. Monitoring lactate therefore provides insight into exercise intensity and fatigue development rather than being the direct cause of fatigue.

How lactate threshold influences training and racing

For shorter endurance events such as 5 km races or time trials, athletes often compete close to or slightly above LT2. For longer events such as half marathons, marathons, and long cycling races, performance is typically maximised just below LT2.

Understanding individual thresholds allows athletes to pace races more effectively and avoid early fatigue. It also helps ensure training sessions target the correct physiological systems.

How to assess lactate threshold

Laboratory testing

The most accurate method of determining lactate threshold is graded exercise testing with blood lactate sampling. During these tests, intensity is progressively increased while small blood samples are taken to identify LT1 and LT2.

Field-based methods

When laboratory testing is not available, field tests such as 30-minute time trials, heart rate analysis, and perceived exertion can provide reasonable estimates of threshold intensity. While less precise, these methods are practical and repeatable.

Wearable technology

Modern training watches estimate lactate threshold using heart rate, pace, and performance trends. These estimates are useful for day-to-day training guidance, though they should be interpreted cautiously.

Training to improve lactate threshold

Improving lactate threshold requires a balance of volume, intensity, and recovery. Training below LT1 builds the aerobic base that supports higher intensities. Targeted threshold sessions near LT2 improve lactate clearance and tolerance.

Common approaches include tempo runs, long intervals at threshold intensity, and controlled progression of workload across training blocks. For most athletes, one focused threshold session per week is sufficient when combined with high volumes of low-intensity training.

Common mistakes in threshold training

A frequent mistake is performing too much training at or above threshold intensity. This leads to excessive fatigue and reduced adaptation. Successful threshold training relies on discipline, patience, and respect for recovery.

Conclusion

Lactate threshold provides a powerful framework for understanding endurance performance. By distinguishing between LT1 and LT2, athletes can structure training more effectively, improve race pacing, and manage fatigue across a season.

Training to improve lactate threshold is not about pushing harder every session. It is about applying the right intensity at the right time, supported by adequate recovery.

References

Benítez-Muñoz, J.A. et al. (2023) Blood lactate, exercise intensity and endurance performance. Sports Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC9353623/

Casado, A. et al. (2023) Lactate-guided training intensity distribution in endurance athletes. International Journal of Environmental Research and Public Health. https://www.mdpi.com/1660-4601/20/5/3782

Faude, O., Kindermann, W. and Meyer, T. (2009) Lactate threshold concepts: how valid are they? Sports Medicine. https://pubmed.ncbi.nlm.nih.gov/19453206/

Seiler, S. (2010) What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance. https://pubmed.ncbi.nlm.nih.gov/20554741/

Wackerhage, H. et al. (2022) The lactate threshold concept: physiological background and practical application. Sports Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC9353623/

Polar (n.d.) Lactate threshold explained. https://www.polar.com/en/journal/lactate-threshold

TrainingPeaks (n.d.) The importance of lactate threshold training. https://www.trainingpeaks.com/blog/the-importance-of-lactate-threshold/