Aerobic threshold

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Lactate performance curve of a treadmill ergometer test. There is no clearly identifiable aerobic threshold and the values ​​would vary widely depending on the method used.

The aerobic threshold (AS) , also known as the minimum lactate equivalent or basic lactate , is a term used in exercise physiology . In terms of the basic idea, this is the lowest exercise intensity at which the muscles no longer work purely aerobically for a longer period of time and an increase in the lactate value in the blood compared to the resting value can be measured. The term aerobic threshold is rarely used today; instead, only basic lactate or minimal lactate equivalent is spoken of.

Physiological background

According to the threshold theory, the energy requirement of the working muscle is completely covered by the aerobic metabolism (oxidation of fatty acids and citric acid cycle ) up to this threshold . When the load increases, more lactate is produced in the working muscles due to the increasing anaerobic lactic metabolism (lactic acid fermentation) than is broken down by them themselves, so that more lactate is transferred into the blood. This can be determined by an initial slight increase in blood lactate levels. The lactate can be transported away and broken down by the organism relatively quickly and without problems, so that no further increase in the lactate concentration occurs ( steady state ) even with prolonged exposure at the same intensity .

If the load exceeds this, the muscle groups concerned work in an aerobic-anaerobic transition. Only with a further increase in load does a decrease in performance occur. However, this drop in performance has various causes and, according to current scientific knowledge, cannot be attributed to the increased lactate concentration or the exceeding of a certain threshold (e.g. anaerobic threshold ).

Aerobic threshold level

The aerobic threshold is reached on average at 70–80% of the individual anaerobic threshold (IAS) and a blood lactate level of around 2  mmol / l (resting value around 1 mmol / l). This corresponds to an average heart rate of around 160 beats per minute. This value was previously set as a fixed threshold, although variable thresholds have now become established in sports medicine.

meaning

An athletic load on the aerobic threshold can be sustained over a long period of time because of the completely aerobic energy supply . Endurance training in this area is referred to as extensive endurance training or fat metabolism training, as the necessary energy can be covered almost entirely by metabolizing fatty acids. Such training can also be carried out as a regeneration measure.

From the aerobic threshold, a noticeable increase in stress hormones and a decrease in base excess can be measured as an indication of the buffering of acidic valences and a decrease in the pH value . The oxygen equivalent also increases.

In Dickhuth's lactate threshold concept , the anaerobic threshold is set at a blood lactate concentration of 1.5 mmol / l above the aerobic threshold.

criticism

The concept of the aerobic threshold is controversial. According to the German sports scientist Horst de Marées, there is no physiological basis for the term aerobic threshold. Instead, only the aerobic-anaerobic threshold is important. Since the processes of energy supply flow into one another, the idea of ​​fixed thresholds for certain lactate values ​​is no longer the current state of research. Furthermore, lactate is now not viewed as an end product, but as an intermediate product in the energy supply, which is produced even when the energy is supplied purely aerobic and which is converted back into pyruvate . Theoretically, an increase in the lactate concentration could be measured even with a purely aerobic exercise, since the pyruvate concentration also increases.

Confusing definitions of terms

In the international literature, the German term aerobic threshold is referred to as anaerobic threshold or lactate threshold , which, however, has nothing to do with the German anaerobic threshold . The name goes back to the definition of Wasserman, who defines the anaerobic threshold as follows: The anaerobic threshold is the performance above which the oxidative energy production is supported by anaerobic mechanisms. This intensity of exercise is accompanied by an increase in lactate and the pyruvate / lactate ratio in the body.

See also

Individual evidence

  1. ↑ a b Kai Röcker: Dispute about the emperor's beard: Which lactate threshold is the best? In: German magazine for sports medicine. Volume 59, No. 12, 2008.
  2. ↑ a b P. Wahl, W. Bloch, J. Mester: Modern ways of looking at lactate: lactate an overestimated and at the same time underestimated molecule. In: Swiss Journal for Sports Medicine and Sports Traumatology 57, No. 3, 2009, p. 104, ( online full-text access (PDF; 206 kB), accessed November 13, 2010).
  3. ^ A b c Hans-Hermann Dickhuth: Introduction to sports and performance medicine. Verlag Karl Hofmann, Schorndorf 2000, ISBN 3-7780-8461-5 , pp. 203-204.
  4. ↑ a b Jürgen Weineck: Sports biology. 10th edition. Spitta, Balingen 2010, ISBN 978-3-938509-25-8 , p. 342.
  5. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 467
  6. ^ L. Bruce Gladden: The role of skeletal muscle in lactate exchange during exercise: introduction. In: Medicine & Science in Sports & Exercise. Issue: Volume 32 (4), April 2000, pp 753-755, abstract
  7. ↑ Urs Boutellier: The aerobic threshold. In: Swiss Journal for Sports Medicine and Sports Traumatology 53 (4), 185–185, 2005, online full-text access (accessed July 16, 2012; PDF; 56 kB)
  8. ↑ K. Wasserman, BJ Whipp, SN Koyl, WL Beaver: Anaerobic threshold and respiratory gas exchange during exercise. In: J Appl Physiol . 35, 973, pp. 236-243. Quoted from: Kai Röcker: Dispute about the emperor's beard: Which lactate threshold is the best? In: German Journal for Sports Medicine Volume 59, No. 12, 2008.