Lactate Threshold. What is it and why does it matter? In this post I’ll seek to answer these two questions with the hopes of clarifying a somewhat confusing topic. Warning: A slight bit of science and data wonkery ahead.

What Is The Lactate Threshold (LT)?

Put simply, the lactate threshold is the point at which your body can no longer maintain equilibrium between lactate production and clearance (1). The current trend in exercise physiology is to split the lactate threshold into two parts, LT1 and LT2.

LT1 is typically recognized as the workload (given in watts) corresponding to a sustained increase in blood lactate concentration above resting levels (typically below 2.0 mmol/L) during progressive exercise (see graphic below).

LT2 is the workload corresponding to a rapid rise in blood lactate signifying the upper limit of sustainable exercise, typically around a blood lactate concentration of 4.0 mmol/L (see graphic below).

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Sustainable Power

This LT2 workload is roughly related to the intensity one might experience in a 60 minute time trial (2). The LT2’s close relationship with sustained power outputs (think climbing and time trialing) is the reason it is the threshold most commonly referenced in current training methodologies and cycling jargon (3).

While over 15 different labels describing the “lactate threshold” exist in the exercise science literature (1), the LT2 is the definition that has emerged as the most applicable to endurance performance.

What It Looks Like

In short, if you’re hearing someone describe their lactate threshold, anaerobic threshold, maximal lactate steady state (MLSS) or functional threshold power (FTP), they’re probably referencing what is currently understood as the Lactate Threshold 2 (LT2). Take a look below for a typical blood lactate curve from a hypothetical lactate threshold test.


Why does it matter?

There are three primary reasons why you should be interested in the lactate threshold (1).

1. The LT2 and endurance performance are closely related (i.e., by increasing your LT2 you improve your chances of getting on the podium).
2. Understanding your LT2 helps to precisely identify and prescribe potentially optimal training intensities (e.g., allows you to maximize your available training time).
3. Your LT2 is an objective measure of your progress on the bike (i.e., you’re either getting stronger or you’re not, no guesswork here).


As you can see, identifying and understanding your LT2 (or FTP for the TrainingPeaks initiated) can be a powerful means to more clearly understand your performance, accurately prescribe training intensities, and objectively measure your progress on the bike.

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1. Gore, C.J. and Australian Sports Commission., Physiological Tests For Elite Athletes. 2000, Champaign, IL: Human Kinetics. xiv, 465 p.
2. Billat, V.L., et al., The concept of maximal lactate steady state: a bridge between biochemistry, physiology and sport science. Sports Med, 2003. 33(6): p. 407-26.
3. Allen, H. and A. Coggan, Training and racing with a power meter. 2nd ed. 2010, Boulder, Colo.: VeloPress. xviii, 326 p.