Lactate threshold
The aerobic threshold ( AS), also referred to as the minimum lactate equivalent basis or lactate, is a term used in sports physiology. Essentially lead it involves the lowest intensity level at which the muscles over a longer period of time no longer works purely aerobic and so an increase in the lactate value in the blood compared with the resting value can be measured. The term aerobic threshold is used now little more, instead, is only spoken of basic or minimal lactate lactate equivalent.
Physiological background
The energy demand of the working muscle is covered according to the threshold theory up to this threshold completely through the aerobic metabolism (oxidation of fatty acids and citric acid cycle ). At a load increase more lactic acid is produced than is degraded by themselves back into the working muscles by increasing anaerobic metabolism laktaziden ( lactic acid fermentation), so that more goes into the blood lactate. This can be determined by a first slight increase in blood lactate levels. The lactate can be relatively quickly and easily removed and degraded by the organism, so that even with prolonged exercise at the same intensity, no further increase in lactate concentration is ( steady state ).
At about continuous stress, the relevant muscle groups in the aerobic - anaerobic transition work. Only with a further increase in load results in a performance degradation. However, this drop in performance has different causes and is according to scientific evidence not attributable to the increased lactate concentration or exceeds a certain threshold (eg, anaerobic threshold).
Level of aerobic threshold
The aerobic threshold is an average of 70-80 % of the individual anaerobic threshold (IAT ) and a blood lactate concentration of about 2 mmol / l ( resting value about 1 mmol / l ) is reached. This corresponds to an average heart rate of about 160 beats per minute. This value was previously defined as a fixed threshold, which have now become established variable thresholds in sports medicine.
Importance
A sporty stress at the aerobic threshold can be maintained because of the completely aerobic energy supply over a long period of time. Endurance training in this area is referred to as extensive endurance training or lipometabolism because the required energy can be almost completely covered by the metabolism of fatty acids. Such training can be performed as a regeneration measure.
From the aerobic threshold a noticeable increase in stress hormones and a decrease in base excess as an indication of a buffering of acidic valences as well as a decrease in pH can be measured. Also the oxygen equivalent increases.
In the lactate threshold concept by Dickhuth the anaerobic threshold at a blood lactate concentration of 1.5 mmol / l is set above the aerobic threshold.
Criticism
The concept of aerobic threshold is controversial. According to the German sports scientist Horst de Marées there from a physiological point of view no basis for the concept of aerobic threshold. Instead, if only the aerobic anaerobic threshold of significance. Since the processes of energy supply smoothly across the idea of fixed thresholds is no longer current state of research in certain lactate values. In addition, lactate is now viewed not as an end product, but as an intermediate in the provision of energy that arises even in purely aerobic energy provision and is converted back to pyruvate. This could theoretically even under a strictly aerobic power, an increase in lactate concentration can be measured, as the pyruvate concentration also increases.
Confusing Definitions
In the international literature, the German term is referred to as aerobic threshold anaerobic threshold or lactate threshold, which has nothing to do with the German anaerobic threshold. The label is to the definition of Wasserman back defining the anaerobic threshold as follows: The anaerobic threshold is that power above which the oxidative energy production is supported by anaerobic mechanisms. This intensity level is accompanied by an increase of the ratio of pyruvate and lactate / lactate in the body.