What is Lactate and Lactate Threshold?

What is Lactate and Lactate Threshold?

Lactate and Lactate threshold, both terms widely used in endurance sports training, yet both are misunderstood! In this article we aim to demystify the terms and explain their advantages and limitations.

Lactate formation occurs as a result of glucose utilisation by muscle cells under aerobic conditions. Dr. George Brooks, a metabolism expert from the University of California at Berkeley demonstrated that lactate was not a waste product, as was previously believed, but instead the most important gluconeogenic precursor, (new glucose generator) in the body. 

With around 30% of all glucose used during exercise derived from lactate “recycling” to glucose, let’s take a look at how this directly affects your performance.     

Lactate and Performance

Lactate as we know, is the byproduct of glucose utilisation by muscle cells. The higher the glucose flow into the cell, the higher the lactate production, independent of oxygen availability! During high intensity exercise, lactate production is many times higher than that of resting levels.

If we observe the differences in blood lactate levels from a World class athlete with that of a junior, we can see how notable the difference is:- 

Workload Junior Cyclist Top Amateurs Avg. Pro-Tour World Class
w/kg Blood La (mmol/L) Blood La (mmol/L) Blood La (mmol/L) Blood La (mmol/L)
3 1.3 1.1 1.1 0.8
3.5 1.8 1.3 1.2 0.8
4 3 2.3 2 0.96
4.5 6.6 3.5 3.2 1.8
5 10 7.6 5.8 3.1
5.5 9.2 8.2 5.2
6 8.9

Differences in Blood Lactate levels (mmol/L) between competitive cyclists of different levels. Table modified from San Millán et al, 2009.

The lower blood lactate levels observed in the top athletes, is due to their enhanced lactate clearance capacity. Well trained athletes are very efficient and export less lactate to the blood as they clear it in higher amounts right in the lactate producing muscle which takes seconds or milliseconds. 1

Dr. Iñigo San Millán, Ph.D, Director of the Exercise Physiology and Human Performance Lab at the University of Colorado advises that lactate testing is probably the best way to assess muscle metabolic stress and performance, especially in endurance athletes. 

So now that we can see just how efficiently well trained athletes’ lactate clearance capacity is, we can begin to use the information to our benefit!   

The Different Lactate Thresholds

LT1 – The first lactate threshold, or the aerobic threshold is used to demarcate zone 1 and 2. LT1 is defined as the lowest intensity at which there is a sustained increase in blood lactate concentration above resting values2

LT2 – The second lactate threshold, or maximal lactate steady state (MLSS) is used to demarcate zone 2 and 3. LT2 is defined as the intensity that causes a rapid increase in blood lactate indicating the upper limit of equilibrium between lactate production and clearance 2.

To better illustrate the training zones, the figure below shows a cyclist’s results from a lactate threshold test, with the 3-zone model overlaid.3 Strictly exercise intensities can only really be split into the 3-Zones below, however most coaches will split the graph down and apply a 5-zone model to allow for more specific training sessions.

Training Misconception Around Lactate Threshold

Lactate threshold, a buzzword amongst endurance athletes! Being able to focus on the special training zones will enable a better understanding of how your body processes lactate and in turn how this can improve/or impede your performance. 

A common training mistake can be to train at the “lactate threshold” in order to improve the lactate clearance ability, however without having a lactate test, you will have no idea about your lactate metabolism and the true heart rate, power or pace where the threshold occurs. Your training should be focussed around sessions with an intensity just below the threshold with the goal of ‘pushing’ the level upwards and likewise sessions with blocks of challenging work above the threshold, with the goal of ‘pulling’ the threshold higher.

The only way though to directly measure lactate threshold is by conducting lactate testing.

VO2 Max testing & Lactate profile 

At ExtraFit, we’re serious about sports science support and have invested in gold standard cardiopulmonary exercise testing equipment. We can offer athletes a safe laboratory environment, with accurate objective testing designed to help improve performance and achieve personal best times!

How does a lactate threshold test work? 

Known as an incremental exercise step test, a lactate threshold test is broken down into segments that progressively get harder. During each segment, we’ll ask you to ride at a certain power output, or run at a certain pace, every three minutes. Once the body has achieved ‘steady ‘state’ we progress to the next higher intensity.

At the conclusion of each segment, we’ll take a blood sample which will measure your blood lactate levels and be plotted onto a graph. At the end of the test we can check the results alongside heart rate, power and pace and determine your lactate threshold. Oxygen uptake levels measured by the metabolic cart throughout also allow us to calculate the percentage of VO2MAX that each threshold occurs at – a really useful way to monitor training benefit and effectiveness. Upon retesting, if your threshold progressively occurs at a higher percentage of your VO2MAX, you can be confident you are getting fitter and therefore faster!  E.g. Your body is able to work at a higher percentage of its absolute maximum without fatigue setting in.

Realistically, how hard is it? 

Well, is anything easy worth having? Jokes aside, this is a test for keen endurance athletes, the lactate profile step test begins at a very low intensity and gets progressively harder with each segment, until you reach around 80-90% of maximum effort. All in all, we’d say you’ll feel the same as you would at the end of a challenging interval session! If you are completing a combined test to also ascertain VO2MAX, it’s the second part of the test after 20 minutes rest where you have to get your ‘game face’ on and work to exhaustion!

How is blood taken? 

It’s just a little prick, it won’t hurt a bit! Using a lancet and a handheld device similar to those used to measure blood sugar levels in diabetics, we’ll take a sample before proceeding to the next segment. 

What will a lactate threshold test tell me? 

LT1 represents the maximum power output at which you should be doing your base rides.

LT2 represents the maximum power output you can sustain with stable blood lactate levels.

Your lactate threshold test will give you actionable data based on your test, and from the results of the graph we’ll be able to see where both LT1 & LT2 kick in and set accurate training zones based on heart rate pace or power. A customised training plan can then be put together enabling us to focus on the correct mix of training that is best for you. 

Would I need a retest? 

If you continue to train at the right level, based on your lactate thresholds, then the only way is up! Your performance will improve and so will your body’s ability to process lactate, so we’d advise periodic retests to assess the efficacy of ongoing training programs.

Are you an endurance athlete looking to improve your performance? Contact us now to organise your VO2MAX & Lactate Profile testing!


  1. Dr. Iñigo San Millán, Ph.D, Director of the Exercise Physiology and Human Performance Lab at the University of Colorado. Via Training Peaks article
  2. Bourdon (2013) Physiological Tests for Elite Athletes
  3. How To Use Training Zones To Enhance Endurance Training, Loughborough University. 
  4. Road Cycling UK Article. Six things you need to know about blood lactate threshold testing.
  5. Train Right Article: The Performance Benefits of Lactate Threshold Testing and Training