Anaerobic exercise

The anaerobic threshold ( ANS), also known as aerobic- anaerobic threshold or lactate threshold, is a term used in sports physiology and refers to the maximum stress intensity, which can be provided by an athlete barely maintaining a state of equilibrium between the formation and decomposition of lactate when so the maximum lactate steady - state is achieved. The anaerobic threshold is mainly determined performance diagnostically and used in the training control when it comes to the derivative of the training areas and other aspects of your training routine. In addition to training with an intensity just below this limit, a high effect in the development of endurance capacity is said.

• 4.1 Individual anaerobic threshold
• 4.2 Threshold models
• 4.3 Criticism of the physiological reasons

History

Already in 1808 it was found by Jöns Jakob Berzelius, the production of lactate in muscle. A century later, the biochemistry of energy metabolism and muscle contraction was examined in detail by a variety of scientists, leading to a deeper understanding of the lactic acid ( which dissociates under physiological conditions as lactate and hydronium ion is present ) led during physical exercise. At this time the now disproved assumption was that lactate is a metabolic end product of glycolysis and with too small a supply of oxygen in the muscle related ( anaerobic ). Today, however, assumed, that the lactic acid fermentation, and thus the production of lactate is a process which depends on the energy conversion and not the availability of oxygen. Thus, an anaerobic energy supply takes place even at rest to some extent.

In the first half of the 20th century the concept of maximal oxygen uptake (VO2max ) was developed by the working group around Archibald Vivian Hill developed and used to determine the anaerobic endurance capacity. Thus, it could be checked and compared for the first time the power state of athletes on a physiological basis and largely independent sport. With time came to criticism of the concept of VO2max, since this a complete physical exertion is required, which depends largely on the individual motivation of the athlete. For example, it is difficult to determine the differences in performance of subjects of the same performance levels only on the basis of VO2max. Another problem represents the high physical stress, for example, in sick patients

In order to test the endurance without maximal exertion, other methods have been developed since the 1960s. The group of Hollmann adopted a point of optimal ventilatory efficiency, corresponding to the first increase in the ventilatory equivalent of oxygen and the arterial blood lactate concentration in a step test. Some years later, this point of Wasserman and McIllroy was called ( in German aerobic threshold ) in a plot of ventilation and oxygen uptake as anaerobic threshold ( LTAN ). At this time, the determination of blood lactate was associated with some problems such that the spirometry has been widely used for the determination of Ltan.

In the 1960s, the lactate concentration of capillary blood was measured using the enzyme method for the first time. This led to an increasing use of blood lactate ( bLa ) as parameters of endurance performance as well as the workload. In the following years numerous lactate threshold concepts have been developed and published a large number of studies on these thresholds. The variety of emerging concepts that often only in a certain application area have reliable values ​​, led to some misinterpretation and confusion.

Definition

Metabolism and lactate concentration

Characteristic of reaching the anaerobic threshold is the fact that the steady state, ie the steady state between lactate production and degradation can no longer be maintained and the surrounding small subsequent increases in performance to a large increase in lactate concentration in the working cell in the blood, in the muscle cells and lead in the interstitium. Is measured in evaluation tests, the concentration in the peripheral blood. The anaerobic threshold has a close relationship to the respiratory compensation point (RCP ) and the pH gradient.

It should be noted that long before reaching the threshold of large amounts of lactate are formed. An understanding that ever used at a certain point the lactate formation only in significant amounts, was still widespread in the 1960s and 1970s under sports medicine and is now considered completely refuted (see lactate shuttle theory). In addition, lactate is not now regarded as a performance limiting factor, but other processes such as acidosis ( acidity ) in the muscle caused by an excess of protons. Therefore, a mere restriction on lactate levels and thresholds in performance diagnosis is questionable, at least from a physiological point.

The anaerobic threshold is the most people in the vicinity of a lactate concentration of the peripheral capillary blood ( ear lobe or finger tip ) of 4 mmol / l This lactate value was therefore often used in the past to define the anaerobic threshold. The value of 4 mmol / l can be considered as average and was determined empirically from respiratory and metabolic conditions found sizes. However, the lactate value at the anaerobic threshold can vary greatly individually, were measured from 2.3 to 6.8 mmol / l Therefore, the basic threshold determination " 4 mmol / L method" is now recognized by the unsuitable.

The lactate concentration in the rest is 1-2 mmol / l, often an initial drop in the concentration of lactate is observed after the beginning of exercise.

Not to be confused with the anaerobic threshold is the aerobic threshold at a lactate concentration of about 2 mmol / l In the aerobic threshold is the lowest intensity level at which an increase in lactate levels from resting value is the first time to measure. This individual aerobic threshold is referred to in sports science as the minimum lactate equivalent basis or lactate. Up to this value fatty acids are metabolized primarily. At about continuous stress, the relevant muscle groups in the aerobic - anaerobic transition work. The resulting lactate can be relatively quickly and easily removed by the body and are terminated ( "steady state "). The concept of aerobic threshold is now controversial.

Energy supply

Depending on the load level of the body gains the converted energy from various sources. There are four types of energy supply. In relation to the anaerobic threshold different situations have to be distinguished:

• At a load below the anaerobic threshold, the energy supply runs not only under metabolism of oxygen, ie from aerobic, but never reaches the anaerobic digestion a measure that exceeds the existing, more pronounced in the trained athlete, ability to rapidly lactate degradation ( cf. above). An endurance performance can be maintained here for a long time, eg when running a marathon.
• A load at the anaerobic threshold, i.e. to a small extent below or above the threshold, is the highest load that can be sustained over the long term. It should be noted that from the point of energy supply such a continuous load limits that are not due to exceeding the anaerobic threshold, as the glycogen reserves during intense endurance are largely exhausted, depending on the training status after 60 to 90 minutes. Within limits, this power loss will be compensated by food intake during the competition (see also catered control).
• At a load above the anaerobic threshold, the energy supply is increasingly carried out anaerobically. The performance is therefore endure only short-term ( few minutes). Still plays with longer competitions, the ability to allocate a further short-term and temporary in the way of anaerobic metabolism significantly more energy in certain competitive situations an important role: for example, the so-called attacks in cycling or at the 5,000 and 10,000 - meter race require, as well as the short-term, fast running sections in all ball sports. In addition to the use of creatine phosphate reserves the anaerobic metabolism of Lactic is the only way to provide benefits that are higher than those yielded by the athletes at the anaerobic threshold.
• If - at the end of a race ( sprint ) or at any time during the competition - leave the predominantly aerobic intensity range, the accumulated lactate is then used by the metabolism of oxygen supply and thus degraded. In this case, the creatine phosphate reserve is rebuilt. For this reason, in a subsequent to the increased performance regeneration phase or end of the competition nor an increased respiration detected ( see more oxygen uptake after work ). The ability of regeneration during the competition is markedly variable, determines very much the athlete type (eg in cycling criterion specialists vs. -Time driver), but can be trained in limits. In addition to the rapid regeneration is the ability to tolerate increased over a limited period blood lactate values ​​of great importance. The training doctrine speaks of " lactate tolerance ", in relation to the metabolism of lactate in the regeneration phase of the "capability of rapid lactate recovery".

Concept names

The term anaerobic threshold is used in both the cardiopulmonary exercise testing as well as in the lactate performance diagnostics. There are different names and abbreviations, some of which are contradictory in English and German. For example corresponds to the English term coined by Aquarius anaerobic threshold ( LTAN ) of the German aerobic threshold and not the anaerobic threshold. The following table lists the different titles will be displayed:

Importance in the performance diagnostics

The anaerobic threshold is of great importance in the lactate performance diagnostics. The ANS can be set to various other performance parameters in relationship. In the training practice, this is the speed (km / h), the cardiac frequency or the power (watts). In sports medical examinations, the unused percentage of VO2max can be specified.

It is common today - make the classification of the training ranges in percentages with respect to the individual anaerobic threshold ( iANS ) - starting from the value determined in step test performance diagnostic results. The stress intensity is divided into intensity zones, which are given in % of the power at the iANS in watts or in % of the heart rate at the iANS, such as " basic endurance - 65 to 75 % iANS " (meaning 65 to 75 % of the power at the iANS ).

Determination

The performance of the (individual) anaerobic threshold by a stepwise exercise test is Determined connected with several blood samples ( ear). By recording the curve a determination of the iANS is more precisely possible. The sharp increase in the lactate performance curve indicates here that the organism could not maintain the steady state. An approximate determination is also a bloodless heart rate / power diagram of possible: From the individual anaerobic threshold, the slope of the heart rate ( kink in the curve) decreases with additional loads. It is known in this context, the Conconi test.

To determine the lactate threshold blood lactate concentration in arterial capillary blood of the earlobe is determined (approximately 20 ul ), for example by means of enzymatic methods. In conducting the tests, it is important that the procedure is in accordance with relevant guidelines. This includes the consideration of various factors influencing the concentration of metabolic size lactate. It is especially important that the intracellular glycogen stores are filled, as they significantly affect the amount of lactate concentration and the shape of the lactate performance curve. At low Glykogenvorräten for example, very little lactate are formed. Thus the Glykogenarmut deceptive in muscle from a good endurance training effect. So in order to make measurement results comparable and to avoid misinterpretation, care must be taken before the test to obtain maximum Glykogenspeicherauffüllung. Also the training program prior to the test should be comparable in different runs. Furthermore, factors such as time of day, blood flow, sweat or urine lactate - lactate important.

Individual anaerobic threshold

The individual anaerobic threshold ( iANS or IAS) has been introduced, as there can be large differences from the fixed threshold of 4 mmol / l, depending on the level of performance. The iANS is defined as the point of lactate power curve where the critical slope begins.

At what power level of the organism reaches or exceeds the anaerobic threshold depends on various - from factors - trainable. These include the density and location of the mitochondria in the cell, the Kapillarisierungsgrad the muscle, the filling state of glycogen, the diffusion capacity of oxygen through the cell membranes, the activity of the enzymes of the respiratory chain and the oxygen binding and oxygen carrying capacity. Prolonged endurance exercise (usually about 5 minutes ) must not lead to a violation of iANS if optimum performance is to be achieved, because after exceeding the iANS after a short time a significant decrease in performance can be expected. Thus, people who achieve their individual anaerobic threshold at a higher power, a more favorable starting position for endurance exercise.

Threshold models

The term Threshold models referred in sports medicine mathematical algorithms to determine the long-term endurance threshold ( individual anaerobic threshold, in short: iANS or IAS ) are used. Since the early 1970s, various threshold models are discussed and tested. Allen individual models were different loading protocols and subject material basis, so that the conditions for the use of the models are different. The main models are:

Criticism of the physiological reasons

Since the mid- 1980s, there is a debate about the terminology and the physiological background of lactate threshold concepts. Early assumptions on lactate production and distribution in the organism are questioned (lactate shuttle theory). Lactate is now seen as a pseudo - hormone ( Lactormon ), has the controlling and regulating function. His contribution to muscular fatigue is doubted.

The division of load areas in aerobic, aerobic- anaerobic and anaerobic workout is from a methodological perspective, although useful, but does not correspond to the physiological events. Thus, the provision of energy takes place partially anaerobically even in calm and even at high loads aerobic metabolic processes are still active. There is also criticism that the lactate increases without clearly visible threshold and run the aerobic or anaerobic energy deployments in parallel and not switch suddenly. The term threshold is therefore misleading. Furthermore, the nature of the test protocol ( step duration and length) have a significant impact on the curve, and thus must be the same for comparing different subjects.