Lactate is often seen as the main performance-limiting factor, but this has long since been scientifically proven wrong. 2PEAK clarifies the facts about this substance and its role in performance diagnostics.
The word “lactate” has a negative connotation for endurance athletes, as they associate it with steep hills and burning legs. “Lactic acid” is often blamed for a decline in performance. However, scientists have debunked this misconception for nearly 30 years. Lactate is actually beneficial—and even essential. But, as with many rumors, once a misconception takes hold, it’s hard to erase. Lactate’s bad reputation is one of these persistent myths.
Here’s what happened: Around the beginning of the last century, physiologists observed that increasing exertion resulted in higher levels of lactate in the blood. From this, a theory emerged that lactate limited muscle power. This misconception laid the foundation for lactate’s negative image: until the late 1970s, lactic acid (lactate) was thought to be a waste product from anaerobic metabolism that limited endurance performance. Even though research disproved this theory nearly three decades ago, lactate’s bad reputation persists.
Lactate is an intermediate metabolic product that plays a crucial role in many bodily processes. It is produced whenever muscle cells burn carbohydrates. Most of this lactate is reused directly in the muscle or transported via so-called transporters to other muscle cells where it is further metabolized. Lactate is also carried through the bloodstream, where it can be used by the heart as fuel—up to 60% of the heart’s energy comes from lactate.
Lactate is continuously produced and broken down, even at rest. However, during intense exertion, more lactate is produced than can be eliminated, leading to a rise in blood lactate levels. Recent studies show that lactate does not limit performance—in fact, it might even enhance it. In experiments with rats, muscle performance increased in animals that were given supplemental lactate. However, blood lactate levels can still serve as an indicator that the body is relying too much on anaerobic metabolism to generate power, suggesting that performance fatigue may be near.
Training concepts
For nearly 40 years, lactate levels have been used as an indicator of endurance capacity in various tests. These tests are all based on the concept of a threshold—a key point relevant to performance and training levels, beyond which the body shifts out of a steady state.
For most analysts, the anaerobic threshold is the key concept. According to prevailing thought, the higher the threshold, the better the endurance performance. The threshold is also a crucial metric for defining training zones (at 2PEAK, the ANS field in training zones). Training zones are generally expressed as a percentage of power at the threshold or translated into corresponding heart rate values.
There are many different definitions and methods for calculating the threshold. The scientifically accurate definition is the power output at the maximum lactate steady state—where lactate production and breakdown are in balance. Lactate concentration at this steady state can vary between athletes depending on muscle fiber composition and usually ranges between 2 and 7 mmol/l.
This balanced state can be accurately determined through several 30-minute constant power tests, but this method is time-consuming, requiring five tests. As a result, a quicker method was sought.
Incremental (Step) Test Concept
This led to the concept of the incremental test, which attempts to determine the anaerobic threshold through spot checks. During this test, power is gradually increased on an ergometer, and at the end of each stage, a blood sample is taken from the earlobe to measure lactate concentration. The anaerobic threshold is determined either from a fixed lactate level (“fixed threshold”) or from a disproportionate increase in blood lactate levels (“individual threshold”).
The starting point for this concept was the observation that runners reached their endurance performance limit at a blood lactate concentration of 4 mmol/l during incremental testing. This gave rise to the (now controversial) 4 mmol/l threshold model. Since these values were often inaccurate for cyclists, other calculation methods were developed to interpret lactate curves differently.
However, this does not solve the main problem. Lactate incremental tests are imprecise and unsuitable for detecting small improvements in performance. Worse still, test results often do not correlate with race performance. This leads to frustration and confusion when athletes who have clearly improved (e.g., higher power output or better race results) show no progress in lactate tests.
As such, the entire method is questionable and useful only as an initial guide. 2PEAK coach Benoit Nave says, “Lactate hasn’t interested me for a long time. It’s not lactate that makes us ride faster or slower.”
The Alternatives
A better approach is to conduct regular maximum power tests over various durations—from sprints to endurance efforts of 20 minutes or more (MP tests). These tests help create a power profile that provides insight into which energy systems are functioning well and which need improvement. The advantage of this method is not only that it is highly indicative but also completely free!
Another diagnostic method that offers additional insights is spiroergometry. This analysis of respiratory gases provides a deeper understanding of the body’s energy production mechanisms. For instance, it can reveal the proportion of fat burning at different performance levels.
Spiroergometry and the different measurements
Fact
Lactate is vital. It enables us to maintain higher levels of performance for longer periods. However, lactate incremental test results should be viewed with caution. They are useful for an initial estimate of an endurance athlete’s potential, but they are insufficient for precisely managing training or tracking performance improvements.
