Lactate threshold

Lactate threshold is the point at which the human body begins to make more lactate, or lactic acid, than it can simultaneously break down. The body creates lactate mainly during intense exercise, when the body requires large amounts of oxygen. Lactate can build up in the body and cause a number of different side effects, including burning muscles. Understanding the lactate threshold is important for athletes. Athletes who exercise just below their lactate thresholds can delay fatigue and maintain performance for longer periods. Exercising just below this level can also help athletes’ bodies take in more oxygen. A person’s lactate threshold depends on more than just exercise. Age, weight, body chemistry, and other factors affect a person’s lactate threshold. Furthermore, people with certain health conditions will have different lactate thresholds.

Background

Intense exercise can be very beneficial for the human body as it increases the heart rate and the amount of oxygen in the blood. This increased oxygen and increased body temperature can also cause a number of different chemical reactions in the body. The chemical reactions that take place in the body are affected by numerous variables. For example, a person’s age, size, sex, and blood type can all affect chemical reactions in the body.

Some chemical changes take place in people’s blood. When people exercise, the body needs to find ways to get energy quickly. The human body completes two functions to produce energy: aerobic and anaerobic respiration. To gain energy through aerobic respiration, the body breaks down glucose. This process requires oxygen. However, when a person is exercising at a high intensity, the body does not bring in enough oxygen to get all its energy from aerobic respiration. The body can also get energy through anaerobic respiration. This process creates energy and does not require oxygen.

When the body does not have enough oxygen, it produces lactate during anaerobic respiration. Although anaerobic respiration is useful because it gives the body energy during intense workouts, the lactic acid can build up in the body, causing negative side effects. Once a person reaches the point in exercise where the body no longer has enough oxygen to break down the lactic acid and the lactic acid begins to build up, that person has reached the lactate threshold.

Overview

As people increase the intensity of their workouts, their bodies’ production of lactic acid also increases. When the body is ridding itself of lactic acid faster than it produces the acid, the body has not met the lactate threshold. A person’s lactate threshold is the point at which lactate begins to build up in the body, causing lactic acidosis. Lactic acidosis does not simply occur when people surpass the lactate threshold and have lactate in their system, but is instead a serious condition typically caused by illness or oxygen deprivation. Lactic acidosis can cause side effects for some people. For example, some people experience stomach aches, nausea, and rapid breathing. Since lactic acid is associated with increased acidity during intense exercise, it can cause a burning sensation in the muscles, but muscle soreness lasting for days is primarily caused by microscopic muscle damage. The effects of lactic acidosis are generally temporary and will usually go away after a period of rest, though the symptoms can be unpleasant when a person experiences them. If, however, the symptoms persist, the person should see a medical professional.

When a person feels the symptoms of lactic acidosis, that person should begin to decelerate their exercise, though it is not generally recommended to stop intense exercise abruptly. Instead, a person can begin to slow the physical activity and eventually stop the exercise altogether. People who experience lactic acidosis should rest and give their bodies time to recuperate before exercising again. People who experience lactic acidosis should also drink plenty of water. Although intense exercise is among the most common causes of the body reaching the lactate threshold, it is not the only cause. Some medical disorders, such as cancer, seizures, shock, and sepsis, can also cause lactic acidosis.

Medical professionals and scientists can determine the lactate threshold through medical testing. To test a person’s lactate threshold, a researcher will have the person perform vigorous physical activity. Then, the researcher will collect blood samples to measure the amount of lactate in the blood. When the body begins to build up lactate, the researchers know a person has exceeded the lactate threshold. Researchers measure lactate threshold to understand more about intense exercise and body function. They also measure the lactate threshold to help individual athletes understand their personal lactate thresholds. Athletes who know their lactate thresholds can measure the intensity of a workout and understand what level of intensity is as high as it can be without passing the threshold. That means the athlete can work out as much as possible without getting the buildup of lactate in the muscles that causes discomfort.

Athletes are interested in lactate threshold. This is because the lactate threshold can indicate the ideal level of exercise intensity. If athletes exercised at lower than their lactate threshold, they would not be working as hard as they could; however, if they worked at higher than their lactate threshold, they would experience lactic acidosis, which would hurt their performance in the end. Athletes who train just at their lactate threshold can actually increase their lactate threshold. When athletes work out, they increase their bodies’ ability to take in oxygen. As a person’s body takes in more oxygen, it can rid itself of more lactic acid. For this and other reasons, most athletes have the goal of increasing the amount of oxygen their bodies can bring in.

Because of athletes’ interests in increasing lactate thresholds and their goal of improving performance, many fitness watches are increasingly incorporating lactate threshold tracking features, helping athletes optimize their training. By monitoring lactate levels in real-time, these devices can help provide insights into when an athlete is approaching their lactate threshold, a key indicator of endurance performance. However, these calculations are more of an estimate and other factors need to be considered when determining a person’s lactate threshold.

Some athletes use interval training to increase their lactate threshold. In interval training, a person performs intervals of extremely intense physical exercise and intervals of much less intense exercise. If athletes feel that the intensity at which they are exercising is too easy, they might be tempted to increase the intensity; however, their bodies will begin to produce excess lactate if they increase the intensity past the lactate threshold. Instead, athletes can increase the duration of their workouts so they can fully exhaust themselves without ever producing an overabundance of lactate and experiencing the negative side effects that lactate buildup can cause.

Bibliography

Craggs, Tom. “How can Runners Improve their Lactate Threshold?” Runner’s World, 22 May 2025, www.runnersworld.com/uk/training/a41865710/lactate-threshold/. Accessed 31 Mar. 2026.

Fetters, Aleisha. “Post-Workout Muscle Recovery: How to Let Your Muscles Heal and Why.” Everyday Health, 22 Mar. 2023, www.everydayhealth.com/fitness/post-workout-muscle-recovery/. Accessed 1 Apr. 2026.

Gardner, Amanda, and Kendall K. Morgan. “Lactic Acidosis and Exercise: What You Need to Know.” WebMD, 18 June 2024. www.webmd.com/fitness-exercise/guide/exercise-and-lactic-acidosis#1. Accessed 31 Mar. 2026.

Ghosh, Asok Kumar. “Anaerobic Threshold: Its Concept and Role in Endurance Sport.” The Malaysian Journal of Medical Science, vol. 11, no. 1, 2004, pp. 24–36, www.ncbi.nlm.nih.gov/pmc/articles/PMC3438148/. Accessed 31 Mar. 2026.

Hyman, Lindsay. “The Performance Benefits of Lactate Threshold Testing and Training.” Carmichael Training Systems, trainright.com/the-performance-benefits-of-lactate-threshold-testing-and-training/. Accessed 31 Mar. 2026.

Kravitz, Len, and Lance Dalleck. “Lactate Threshold Training.” The University of New Mexico, www.unm.edu/~lkravitz/Article%20folder/lactatethreshold.html. Accessed 31 Mar. 2026.

Quinn, Elizabeth. “Lactate Threshold Training for Athletes.” VeryWell Fit, 29 June 2024, www.verywellfit.com/lactate-threshold-training-3120092. Accessed 31 Mar. 2026.

Yeager, Selene. “Lactate Threshold 101.” Bicycling, 30 Apr. 2010, www.bicycling.com/training/a20017067/lactate-threshold-101/. Accessed 31 Mar. 2026.

Železnik Mežan, Lea. “Accuracy of Wearables for Determining the Maximal Oxygen Uptake and Lactate Threshold: A Qualitative Systematic Review.” Frontiers in Sports and Active Living, vol. 7, 16 Dec. 2025, doi:10.3389/fspor.2025.1707991. Accessed 31 Mar. 2026.