Lactate is simply a salt of lactic acid. Hence also the common expression that an athlete is “over acidified” when he can no longer continue running, cycling, etc..
Production of lactate
The lactate value in the blood is the result of continuous production and elimination of lactate throughout the body. This also explains the constant resting lactate value at about 1 mmol/l to 2 mmol/l. An initial drop in lactate concentration is often observed after the start of training.
This means: The so-called “base lactate” can assume a value which is below the resting lactate value. In some sports, lactate values of more than 30 mmol/l can occur. The exact procedure is explained in the article the cell – structure and function.
Decomposition of lactate
The lactate content in our blood also increases with increasing stress. The lactate is partially removed again during physical stress. About half of it is built up in the active skeletal muscles (about 70 percent in the runner!) and 15 percent each in the inactive skeletal muscles, the heart muscles and the liver to glucose (gluconeogenesis).
However, the body can only achieve this by using ATP (“softener” of the skeletal muscles) and energy. But the skeletal muscle also needs both in order to be able to work. The skeletal muscle then lacks this ATP as a “plasticizer”.
Aerobic threshold (also: minimum lactate equivalent, base lactate)
The aerobic threshold is approx. 2 mmol/l and defines the lowest stress intensity at which an increase of the lactate value compared to the resting value is to be measured for the first time. Up to this value mainly fatty acids are metabolized. If the load exceeds this value, the muscle groups concerned work in the aerobic-anaerobic transition.
The resulting lactate can be removed from the organism relatively quickly and easily (“steady state”). The concept of the aerobic threshold has become controversial.
The term anaerobic threshold is a technical term used in sport and performance physiology. It describes the highest possible stress intensity, which can be achieved by maintaining a steady state between lactate formation and lactate breakdown.
The anaerobic threshold is postulated at approx. 4 mmol/lactate. In practice, the lactate value at the anaerobic threshold varies more or less strongly from person to person. For this reason, the determination of the anaerobic threshold according to the “4 mmol/l method” is completely unsuitable.
The only characteristic for reaching the anaerobic threshold is the fact that the steady state can no longer be maintained.
Even small subsequent increases in performance than lead to a sharp increase in lactate concentration in the working cell, in the blood, in the surrounding muscle cells and in tissue. This happens in every person at a different lactate concentration. Values from 2.3 mmol/l to over 9 mmol/l were measured. For this reason, the term individual anaerobic threshold (IANS) is used.
Individual Anaerobic Threshold (= IANS)
A lactate level test the performance at the IANS is determined. It thus refers directly to a lactate value determined individually for this athlete at the anaerobic threshold.
The performance at the individual anaerobic threshold is determined by a stepwise stress test (bicycle ergometer, treadmill, etc.) combined with a blood sample (ear or finger) at the end of each stress level. Today it is usual – based on the performance diagnostic results determined in the lactate level test – to divide the training areas into percentages with reference to the IANS.
The load intensity is divided into 5 different ranges, which are indicated in % of the power at the IANS in watts or in % of the heart rate at the IANS, e.g. “Peak range: 100 % to 110 % IANS” (meaning 100 % to 110 % of the power at the IANS). See also Fig.1. A detailed explanation of the procedure and the evaluation of such a test can be found in the article Lactate level test.
The individual anaerobic threshold is of great importance in performance training since training with an intensity just below this threshold is said to have a high effect on the development of aerobic performance.
IANS significance for training
With respect to the individual anaerobic threshold (IANS), three situations are distinguished:
1. Exposure below the individual anaerobic threshold (IANS)
If the load is below the individual anaerobic threshold, the energy supply is not exclusively provided by oxygen (= aerobic).
However, energy supply without oxygen (= anaerobic) never reaches a level at which more lactate is produced than the body can break down at the same time. A flow equilibrium (= homeostasis) occurs between lactate formation and degradation, the so-called “steady state”.
Endurance performance can be maintained here for a very long time (e.g. for a marathon run).
2. Load on the individual anaerobic threshold (IANS)
A load at the individual anaerobic threshold – i.e. slightly below or above the threshold – is the relatively highest load that can be sustained in the long term.
Here, the organism can just barely keep the balance between lactate formation and degradation.
The glycogen reserves, however, are largely exhausted after 60 to 120 minutes, depending on the state of training, in the case of intensive continuous exercise.
3. Load above the individual anaerobic threshold (IANS)
If the load exceeds the individual anaerobic threshold, the energy is increasingly provided without oxygen (anaerobic).
The performance can therefore only be maintained for a short time.
The higher the load above the IANS, the faster the lactate concentration in the blood rises and the faster exhausted and/or cramped the muscles, the athlete must give up and stop the load.
Athletes who reach their individual anaerobic threshold at a higher performance generally have a more favorable starting position for endurance exertion.
Energy supply as a function of the load intensity
The body gains the energy to be converted from various sources depending on the level of stress. Four types of energy supply are distinguished. Detailed information can be found in the article energy-supply-in-muscle.
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