Aerobic and anaerobic metabolism

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, 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.

Diagnostics of endurance performance

The lactate test is one of the performance diagnostic methods 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 pricked into the ear and then a few drops of blood are taken.

This blood is then examined and the existing lactate value 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 reaching his or her maximum load. If the steps are too short, it is possible for the athlete to reach the maximum speed without being exhausted before.

A lactate test should therefore always have steps of the same length and these steps should be of an appropriate length.In addition, the treadmill can be adjusted with or without gradient, which again affects the step and test length. In addition to the treadmill, a step test can also be performed on a bicycle ergometer or rower 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 personnel are needed to ensure a controlled performance. There are several models for such a step test.

One model includes e.g. 5% incline of the treadmill and starts at 8 km/h. This speed is maintained for three minutes and then increased by two 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 device as described above, or by using the step length and the slope. However, it is particularly important to always carry out 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. ).