Anaerobic threshold: What it is and how it affects my athletic performance

During the performance of a staggered muscle effort, the intensity corresponding to the sharp increase in blood lactate concentration is referred to as the «Anaerobic Threshold».

What is the anaerobic threshold?;

In other words, the term «anaerobic threshold» refers to the speed of movement or the percentage of Vo2max (Maximum Oxygen Uptake) of an aerobic activity where a certain accumulation of lactate in the blood is observed or where the accumulation of lactate shows an increase greater than resting levels. According to researchers, this intensity is energetically equivalent to 50-60% of VO2max for sedentary individuals, and 65-80% for trained individuals ⁽¹⁾.

The concentration of lactate in the blood depends on the intensity, duration, frequency and type of exercise. During prolonged efforts the lactate concentration decreases, whereas during intermittent exhaustive exercise it reaches a maximum value. In exercises where less muscle mass is used the concentration is lower and the rate of removal is faster during active recovery.

Other terms that have been used to describe the phenomenon in the international literature are «Anaerobic Lactate Threshold», «Maximum Stable Concentration of Lactate», «Atomic Lactate Threshold«, etc., however the term »anaerobic threshold" is one of the most common

But what is lactate;

The lactate (lactates) and lactic acid (lactic acid) are quite similar compounds, but they differ because of the presence of a hydrogen atom! In order to understand the difference between these two terms, we need to go into the territory of chemistry, where an acid is called a substance that can give hydrogen ions (H+).

In the present case, therefore, when the lactic acid give a hydrogen ion the resulting product is the Milk. In other words, lactate is derived from the breakdown of lactic acid during anaerobic glycolysis

So what is anaerobic glycolysis?;

It is the process in which metabolic processes associated with the degradation of glycogen, which is used for efforts requiring short-term energy (glycolytic system), take place. Glycogen is essentially the storage form of carbohydrate in muscle cells and the liver. At physical rest, glucose in the blood is stored as glycogen, whereas during exercise it is broken down for energy production. In summary, anaerobic glycolysis involves the breakdown of glucose for energy production.

During the intermediate reaction of glycolysis, hydrogen ions (H+) are produced, which are transferred to a receptor with the coenzyme NAD. If a hydrogen ion receptor is not found glycolysis stops, no energy is produced and muscle activity becomes problematic.

Thus, pyruvate (the end product of anaerobic glycolysis) becomes an acceptor of H+ atoms and is reduced to lactic acid in intense efforts lasting up to 60’’ or 120’’, where there is an oxygen deficiency. Thus, the importance of lactic acid lies in the fact that it is a forced receptor of H+ atoms under anaerobic conditions (as oxygen is a receptor under aerobic conditions)⁽²⁾.

Simply put, the production of lactic acid essentially allows the continuity of essential metabolic processes and thus the maintenance of energy production. It was once thought that lactic acid was a useless metabolite and the cause of muscle burn leading to the cessation of athletic effort. However, as has been found this is not true.

Lactate and calamine

The camming refers to the reduction in performance from 40% to 60% in short-lived 30’’ efforts and is unavoidable in supermax efforts. The nature of the carcass depends on the intensity and duration of the muscle effort.

In earlier research, an increase in lactic acid concentration was associated with a reduced ability to produce muscle work, but today we know that it is not lactic acid per se that causes a decrease in performance but in fact it is the accumulation of hydrogen ions released from lactic acid and their slow removal!

The release of hydrogen ions results in a disturbance of the acid-base balance, with a decrease in pH and the creation of an acidic environment. This intracellular acidosis can cause catabolism in 3 ways:

1. By inhibiting the action of certain enzymes that regulate glycogenolysis and glycolysis.
2. By blocking the formation of the transverse bridges of actomyosin, an essential process for the ability to produce muscle strength.
3. With the interference of calcium transport and calcium transport in the final kinetic plate.

Four main mechanisms of explanation have been proposed for the phenomenon of increased blood lactate concentration, including muscle hypoxia, reduced lactate efflux, rapid contraction fiber recruitment and glycolytic acceleration. Therefore, the use of other terms such as «Onset of blood lactate accumulation» (OBLA) has been proposed.

Finally, three methodological approaches are used to determine the anaerobic threshold: The lactate threshold, the respiratory threshold and the heart rate threshold, with the first method prevailing⁽²⁾.

Conclusion

The anaerobic threshold is a reliable indicator of aerobic endurance, without being more predictive than VO2max. Thus, in aerobic endurance activities where athletes have similar VO2max levels to each other, the winner will usually be the one who has the ability to maintain aerobic energy production at the highest VO2max, with as little accumulated lactic acid in the muscles and blood as possible.

Therefore, athletes participating in aerobic events can and should improve their anaerobic threshold by training with increased levels of lactate in the muscles and blood in order to maximise training adaptations.

By Nandia Markopoulou - Teacher, Athens