Lactate Testing - Specialists and Information

Lactate is a salt of lactic acid. It is produced mainly in muscles under stress as an intermediate metabolite during the breakdown of sugar. It forms when there is insufficient oxygen available for the oxidation of fats and carbohydrates.

In the liver, the body further breaks down lactate to provide energy. This process occurs much more slowly than when there is sufficient oxygen. Therefore, as lactate concentration in the muscles increases, performance declines or breaks down.

Intensive strength and endurance training can raise the threshold at which lactate begins to accumulate, leading to improved performance.

Increased lactate production accompanied by a loss of performance can be unpleasant and frustrating for the ambitious competitive athlete. This is especially true when the athlete is forced to end the competition prematurely.

Lactate pushes the athlete to their physical limit. It has a protective effect on the muscles and the athlete’s overall circulatory system.

Intense physical activity causes a rise in blood lactate levels @ Vadim /AdobeStock

Lactate is produced when, during physical exertion, there is not (or no longer) enough oxygen available for energy production. Instead, the body breaks down sugar (glucose) from its own stores (in the muscles and liver) to produce energy.

Lactate is an acidic byproduct of this oxygen-deprived metabolic process. It accumulates primarily in the muscles.

If the body accumulates more lactate than it can break down, medical professionals refer to this as reaching the anaerobic threshold. Lactate or lactate performance testing can determine when this threshold is reached in individual cases.

Lactate testing is an important diagnostic procedure in sports medicine for assessing an athlete’s individual exercise capacity. It is used to determine the athlete’s anaerobic threshold.

Based on this data, coaches create a training program tailored to the athlete. This process is essential to prevent the body from being constantly overloaded or underchallenged.

Lactate testing is also used to measure the body’s acid-base balance. Acidosis can result from an overproduction of lactic acid (lactic acidosis).

This can also occur during shock caused by massive fluid or blood loss. Cardiogenic or infection-related shock often leads to life-threatening oxygen deprivation and tissue acidosis.

Cancer and other medical conditions, as well as certain medications, can contribute to the development of metabolic acidosis.

In such cases, the blood lactate level can provide important information about the patient’s condition and their further treatment. Respiratory acidosis results from insufficient exhalation of carbon dioxide; in this case, the lactate level is normal.

Oxygen-independent energy production provides only a short-term energy boost. Reaching the lactate threshold is more likely to be accompanied by a decline in performance.

The point at which the transition from aerobic (with oxygen) to anaerobic (without oxygen) occurs depends on the athlete’s level of fitness.

As a rule, the lactate threshold is reached at a lactate level of about 4 mmol/l. However, this is only a guideline. The lactate level of a person at rest should be between 1 and 2 mmol/l.

A significantly elevated lactate level can lead to health problems. However, a lactate concentration in the range of the aerobic-anaerobic threshold is beneficial for the athlete’s performance.

This leads to an enlargement of the mitochondria (the so-called “powerhouses” of muscle cells).

Energy production and oxygen uptake take place in the mitochondria. Excessive lactate production occurs only when more oxygen is needed during exercise than is available.

Lactate is typically broken down through two different pathways. Moderate stress on the muscle cells promotes this breakdown. Per minute, the body breaks down or metabolizes approximately 0.5 mmol/L of the lactate present in the blood.

The two pathways of breakdown are:

1. Increased cellular respiration, in which sufficient oxygen becomes available again for cellular respiration. This results in the conversion of lactate back into pyruvate (an important intermediate product of aerobic/anaerobic metabolism).
2. Lactate is transported via the blood to less active muscles and organs (liver, kidneys, and heart). There, the body burns the lactate or converts it into glycogen, which serves as a carbohydrate store in the liver. (Carbohydrate store).

To determine an athlete’s endurance capacity, a step test or lactate step test is used. This is typically performed on a treadmill or stationary bike. 

At regular intervals, the physician draws blood from the athlete and measures the lactate level in the body. Just a few drops of blood from the earlobe are sufficient to determine the lactate level painlessly.

The step test continues until the athlete reaches their maximum performance limit. In addition to determining the lactate threshold, the physician measures the highest lactate level in the blood. 

Both the duration of the test and the length of the individual stages depend on the individual athlete. This provides important data for an optimal training regimen, which is particularly significant in endurance and competitive sports. 

For this reason, such tests are usually conducted by a sports physician who is appropriately trained and equipped with the necessary equipment.

There are various methods for conducting such a step test.

A common procedure is:

• A 5% incline on the treadmill at an initial speed of 7–8 km/h. 
• After 3 minutes, the speed is increased by 2 km/h.
• After each 3-minute interval, there is a short break during which a blood sample is taken from the earlobe.
• The test continues at a higher intensity

The standard test does not require a treadmill incline. It proceeds as follows:

• Each stage lasts 5 minutes
• A 30-second break for blood collection from the earlobe
• Then, increase the speed by 2 km/h 
• Beginners usually start at a treadmill speed of 5–6 km/h, while advanced participants start at 8–10 km/h.

The step test is over when the subject is completely exhausted and has reached the limit of their performance capacity. This point corresponds to the performance threshold. 

The lactate level measured here is usually 4–6 mmol/l, and the maximum heart rate is 160–200 beats per minute (depending on age). 

During exercise, the lactate level initially rises slowly. Once it reaches a value of about 4 mmol/l, it then rises very quickly and steeply (exponentially). At this point—the transition from the flat to the steep curve—lies the athlete’s anaerobic threshold. The measured treadmill speed at the anaerobic threshold is important for further training planning.

A lactate test always involves testing the body’s exercise and performance limits. The cardiovascular and cardiopulmonary systems are strained and challenged far beyond normal levels. Therefore, individuals should undergo a lactate test as part of a sports medicine evaluation only if they are in good physical health.

A medical examination and a review of medical history should always take place before the test begins.

Blood pressure measurement during a stress ECG @ malkovkosta /AdobeStock

High-risk patients suffering from high blood pressure or coronary heart disease require careful monitoring. Medical supervision during the stress test, including a stress ECG and blood pressure monitoring, is strongly recommended.