Lactate thresholds
Definition of lactate thresholds
Lactate is a metabolic product of the so-called anaerobic lactic glucose metabolism.
This metabolic pathway enables energy to be supplied from glucose without oxygen (? Anaerobic). In addition to the energy source ATP (= adenosine triphosphate), lactate, a salt of lactic acid, is also produced.
At rest, the lactate reference range is 0.9 to 2.0 mmol / l. This value can vary slightly from person to person, so that 1.8 mmol / l is chosen as a rough guide.
The lactate / lactate threshold is usually measured in the capillary blood of the earlobes. Lactate is thus produced, among other things, when the body needs energy quickly. The anaerobic glucose metabolism can guarantee the supply of energy for 20-40 seconds at almost maximum output. In general, about 1.3 mmol / l lactate are formed per hour in the human organism. In addition to the skeletal muscles, it is formed in the brain, skin, intestines, kidneys and blood cells. As long as the build-up and breakdown of lactate is in balance, it is known as a "steady state". By the way, lactate is used up to 60% by cells of the heart muscle.
However, if the body now produces more and more lactate due to intense physical exertion, without the organism complying with the breakdown, the so-called lactate threshold is approached. This lactate threshold is approximately 4mmol / l and has the synonyms “anaerobic threshold” or “anaerobic-aerobic threshold”. As long as this threshold has not yet been reached, an increase in performance is possible. However, if the 4 mmol / l is exceeded, the lactate value rises suddenly and the stress cannot be sustained for long, but only for a few minutes, due to overacidification of the muscles. Therefore, exposure below the lactate threshold is optimal and worth striving for.
meaning
The lactate value has both in the medicine as well as in Sports a big meaning.
In medicine, a high lactate level indicates one Lack of oxygen of the organism, is therefore a so-called Ischemia marker the on a lack of blood flow indicates. There the pH value drops keep going down and there is a risk of Acidosis (Hyperacidity). In the sporting field, lactate value determination is nowadays essential for the performance diagnostics -and control become. Lactate value will usually in the peripheral blood, mostly in Capillary blood of the earlobe measured.
Lactate determination
The principle for Determination of lactate levels in the blood is based on the photometric determination of a dye which with the addition of two Enzymes arises. More precisely, these are the two enzymes Lactate oxidase ("LOD") and Peroxidase ("POD"). That reacts first in blood present lactate with the lactate oxidase too Pyruvate and H2O2. In the next reaction step, after adding 2 substances (4-aminophenazone and 4-chlorophenol), the dye is produced with the help of peroxidase Quinone imine. This can be measured at 520 nm with a photometer so that it is possible to draw conclusions about the lactate values present in the Capillary blood of the earlobe to pull. It is important that the reagent also contains a glycolysis inhibitor in addition to the blood, enzymes and substances. This prevents namely that contained glucose during the measurement in Lactate which would lead to falsely high lactate levels. Since the two enzymes are named, this principle of determining the lactate value is also used LOD-POP method called.
Importance of performance diagnostics in sport
Nowadays it is common the individual Lactate threshold to determine thereby his personal Performance limits to recognize and optimize. Especially for the endurance performance Training in the area of the lactate threshold explained above is particularly effective and a resulting increase in performance has meanwhile been proven in some studies. The higher the threshold, the greater it is Lactate tolerance of the physical organism against the salts of lactic acid. This means that the personal lactate threshold describes the person's ability to tolerate certain lactate levels and to be able to maintain the exposure. By targeted training the lactate threshold can be increased. A higher threshold would then make it possible, for example a marathon in a better time to run. This so-called Shifting the lactate threshold can not with a general training plan but only with individually adapted exercises can be achieved after a corresponding analysis of the lactate values depending on other factors. An important variable that plays a role here is that Heart rate. The heart rate increases as the pace increases. This increases linearly in comparison to the lactate value; the lactate value, on the other hand, increases exponentially. As soon as the lactate threshold is exceeded, there is a sudden increase.
In lactate performance diagnostics, lactate is usually determined with a Multi-stage test. This serves for a more precise determination of one's own lactate values in connection with the heart rate, i.e. certain Pulse values, bring to. The indication of the lactate threshold with 4mmol / l is only a generalized value, which can vary between 1mmol / l more or less. The “IANS”, i.e. the individual anaerobic threshold, can therefore be determined with the multi-stage test. To do this, the person in question either runs outdoors or on the treadmill. It will the speed or. the intensity gradually increased in fixed levels (? therefore multi-level test). After each increase, the individual performance is determined by measuring the lactate value in the capillary blood of the earlobe. With the help of a specialized Computer program can the values analyzed and in one Lactate curve being represented. Using the lactate curve, both the lactate concentration and the pulse values present at the respective point in time can be read off. This enables an objective assessment of the load limits; especially when it comes to increased performance in the form of a shift in the lactate threshold.
