Evaluation of the lactate test | Lactate certificate

Evaluation of the lactate test

The evaluation of a lactate test focuses mainly on the aerobic-anaerobic threshold. It is the most important value for the control of endurance training, because it indicates whether the lactate value is leveling off at a lactate steadyy-state or continues to rise. Lactate steady-state means that after each increase in exertion to a new level, the lactate level in the blood settles down at a certain level and remains at that level with the same intensity.

When the aerobic-anaerobic threshold is reached, the lactate steady-state disappears and the blood lactate level rises steadily without leveling off. This aerobic-anaerobic threshold is at about 4 mmol lactate per liter of blood. Although this value is not one hundred percent accurate, it is a good guide.

One should always bear in mind that this threshold is highly individual and can vary from athlete to athlete, depending on the type of sport and training condition. If the threshold value of 4 mmol lactate per liter of blood at 14 km/h was determined in a classic step test, a repeat test can be carried out after a certain training period to check whether the training has brought about an improvement in endurance performance. Reaching the aerobic-anaerobic threshold at 14 km/h is a very good value for a recreational athlete and in this example no strong improvements through training can be expected.

Lactate curve

In a lactate test, the so-called lactate value in the blood is determined to determine the fitness level of a person. Lactate is produced directly in the muscles and is a salt of lactic acid. The lactate value of a person at rest is one mill mol (mmol) of lactate per liter of blood (1 mmol/l).

This value can rise to 25 mmol lactate per liter of blood (25 mmol/l) under stress. This metabolic product is produced during intensive endurance training, at the beginning of heavy static muscle work and during rapid strength training (longer sprinting distances). The energy required for this is mainly produced by splitting ATP.

What exactly ATP is, would take up too much space here. However, it is important to note that when ATP provides energy, a hydrogen ion (proton) is split off and remains in the muscle. This proton (H+) can lower the pH value in a certain number.

The pH value of the muscles is normally neutral (7). If the value falls below seven, then we speak of an acidic pH value. A lowering of the pH-value can lead to cell damage.For this reason the body has developed a defense mechanism.

To bind the protons, the body produces more lactate. During the formation, protons are bound and the overacidification of the muscle is counteracted. This protective mechanism reaches its limits at some point.

If the pH value in the muscle cell continues to drop while the number of protons continues to rise, then the protons ultimately block the ATP cleavage and the muscle cramps (colloquially: closes up). The lactate thus ensures that a highly intensive load can continue for a certain time before the muscle cramps. The more lactate there is in the blood, the higher the number of protons in the muscle and the greater the strain on the body.

On the basis of the lactate in the blood, the degree of strain can be determined and the body’s ability to maintain intensive strain for a certain period of time. There are two metabolic pathways for physical stress. One is the aerobic energy metabolism, in which the energy supply for the muscles is based on oxygen.

Aerobic means that oxygen is sufficiently involved in the energy supply. If the intensity of a training or competition increases, the muscles need more oxygen to cover the higher energy demand. Above a certain intensity, the body is no longer able to supply more oxygen and the maximum oxygen intake is reached.

Once this point is reached, the body is at the aerobic-anaerobic threshold (4 mmol threshold). From this threshold, the body slowly but steadily begins to consume more oxygen than it is supplied with. The muscle cell is flooded with more and more protons and even more lactate is produced.

To determine this individual threshold, a lactate test is performed. The lactate test is one of the performance diagnostic procedures for determining the endurance ability of an athlete. The longer a load can be increased or maintained, the better the athlete’s endurance ability.

Such performance diagnostics to determine the endurance capacity is usually carried out in the form of a step test. Usually such a step test is done on the treadmill. Optionally, a respiratory gas analysis can be performed to determine further parameters.

Classically, only a lactate test is performed. With a step test the load is increased step by step. Before, during and after the step test, blood is taken from the athlete.

A needle is used to make a small prick in the ear and then a few drops of blood are taken. This blood is then examined and the lactate level in it is determined. The test is carried out until the athlete is absolutely exhausted in order to determine the maximum lactate concentration in the blood in addition to the aerobic-anaerobic threshold.

A step test requires certain guidelines that should be followed. The length of the test plays an important role. If the individual steps are too long, the athlete may become exhausted before he or she has reached maximum load.

If the steps are too short, it is possible for the athlete to reach the maximum speed without being exhausted beforehand. A lactate test should therefore always have equally long steps and these steps should be of an appropriate length. In addition, the treadmill can be adjusted with or without gradient, which in turn affects the length of the steps and test.

In addition to the treadmill, a step test can also be performed on a bicycle ergometer or rowing ergometer. This depends on the original sport of the athlete. Usually, such performance diagnostic step tests are found in competitive sports.

In recreational and popular sports, they occur only rarely, since the effort is correspondingly high and trained specialist personnel are required to ensure controlled performance. There are several models for such a step test. One model includes e.g. 5% incline of the treadmill and starts at a speed of 8 km/h.

This speed is maintained for three minutes and then increased by 2 km/h every three minutes. Blood is taken during and after the exercise. The following standard test is similar.

Each step is completed for five minutes on the treadmill and there is no incline of the treadmill this time. After each stage, a one-minute break is taken and blood is drawn from the subject to determine the lactate level. The test begins at 3.25 m/s (meters per second).

The increase at each step is 0.25 m/s.A step test should always be performed with affinity to the sport. This can be done by choosing the equipment as described above, or by using the step length and the slope. However, it is particularly important to always perform a lactate test under the same conditions and with the same settings in order to be able to compare the various individual tests with each other.

The described way of performing the test refers to a laboratory. In a laboratory, the conditions can be reproduced at any time so that the results are perfectly comparable. However, this is often too far away from reality, so that so-called field tests are also carried out.

These are step tests in the usual environment of the sport (running track, rowing boat, etc.). The evaluation of a lactate test focuses mainly on the aerobic-anaerobic threshold. It is the most important value for the control of endurance training, because it indicates whether the lactate value is leveling off at a lactate steadyy-state or is continuing to rise.

Lactate steady-state means that after each increase in exertion to a new level, the lactate level in the blood settles down at a certain level and remains at that level with the same intensity. When the aerobic-anaerobic threshold is reached, the lactate steady-state drops away and the blood lactate value rises steadily without leveling off. This aerobic-anaerobic threshold is at about 4 mmol lactate per liter of blood.

Although this value is not one hundred percent accurate, it is a good guide. One should always bear in mind that this threshold is highly individual and can vary from athlete to athlete, depending on the type of sport and training condition. If the threshold value of 4 mmol lactate per liter of blood at 14 km/h was determined in a classic step test, a repeat test can be carried out after a certain training period to check whether the training has brought about an improvement in endurance performance.

Reaching the aerobic-anaerobic threshold at 14 Km/h is a very good value for a recreational athlete and in this example no strong improvements through training can be expected. On the y-axis the lactate value in the blood is displayed in mmol and on the x-axis the load values of the step test in km/h. The individual threshold is marked with a red dot and is just under four mmol lactate per liter of blood at just over twelve km/h.

The graph also shows that lactate production increases more the longer the test is run and the higher the load speed. The lactate test is one of the standard means of determining endurance performance and should no longer be missing from any performance diagnostics in professional sports.