Lactate test

The attached figure shows the results of a typical lactate test using the example of a 56-year-old woman, 157 cm tall, 83 kg body weight. The initial load is given as 0 watts. The load was increased by 30 watts every three minutes. After three increases, the test person had reached a lactate value of 4.2 mmol/l, which is sufficiently high for sensible training planning in health sports. Higher loads are not necessary to determine the heart rate at which the test person should train and should be avoided! Endurance loads are only relevant for competitive athletes!

Many evaluations only use one diagram for display, but this also contains a secondary axis. For routine use, we have found it much simpler and less prone to error to use two separate diagrams – one showing lactate as a function of performance and the other showing lactate plotted against heart rate. (Especially for the test persons, representations using a secondary axis are usually too complex). Based on the lactate threshold concept, the training intensity can thus be indicated both as power and as a target heart rate. For the advantage of specifying in the form of heart rate, see here.

Termination criteria

for the examination are:
– occurrence of symptoms
– increase in blood pressure to > 230 – 240 systolic
– palpitations
– nausea
– exhaustion
– clear exceeding of the lowest lactate value by more than 2 mmol/l ( exceeding of the 2nd lactate threshold; _LT2). Higher lactate values – if possible in conjunction with spiroergometry – are only useful for competitive athletes who want to know their maximum performance.
– Reaching the maximum target heart rate [(220 – age)*0.9]

It is particularly important for people with special risks during sport – such as patients with heart or lung diseases of any kind – to limit the reasonable load. For these patients, an exercise ECG should be carried out by the family doctor, whereby the simultaneous determination of the lactate values is an important parameter for assessing the exercise capacity during training, for training control. If only an exercise ECG is performed without determining the lactate level, experience has shown that the heart rate recommended to the patient is too high.

What should be avoided at all costs is uncontrolled exercise for patients with heart or lung disease without any controls! Experience has shown that people at risk often exercise too intensively and are helpless without clear recommendations. If these test subjects refuse to have an exercise ECG performed by their GP, it is certainly better to have the exercise monitored by a well-trained trainer than to allow the patient to exercise uncontrollably on their own responsibility. If the doctor has only carried out an exercise ECG without determining the lactate, the patient is often recommended too high a heart rate. Even at higher heart rates, the ECG shows no evidence of a circulatory disorder of the heart. At the recommended heart rates, however, the 2nd lactate threshold is often significantly exceeded with negative consequences. For this reason, we recommend – even if an exercise ECG has been performed – that you always have a lactate test available for training control.

Lactate, where does it come from, what does it do?

(for more details, see Where does the lactate come from?)

Lactic acid is constantly produced in our organism by splitting glucose to produce 2 molecules of ATP – the chemical fuel of our organism. At a normal pH value, lactic acid immediately splits into ^lactate and ^hydrogen+ ions. At the same time, however, lactate is used by the inactive muscles, for example, and particularly importantly by the heart muscle, and also by the brain to generate energy using oxygen. It is also supplied to the liver for gluconeogenesis, the formation of glucose. As a result of formation and breakdown, the lactate concentration in the blood is between 0.6 and 2.4 mmol/l under resting conditions.

As described in the chapter on energy metabolism during exercise, our organism has an “emergency reserve” of energy-rich phosphates for a few seconds, which allows it to adapt immediately to high physical exertion. As it takes some time before the organism can offer the muscles considerably more oxygen than is required at rest, energy is also produced in the meantime without the use of oxygen, anaerobically during the breakdown of glucose to lactate.

With increasing physical exertion, there is another increase in lactate in the blood. It used to be assumed that from the point at which lactate rises, more glucose is metabolized without the use of oxygen, i.e. anaerobically. This is why the literature refers to the aerobic threshold, the aerobic-anaerobic transition if the lactate continues to rise and finally the anaerobic threshold.

However, if one calculates the contribution of lactate, which is additionally measured in the blood, to the energy supply, it can be seen that the proportion of lactate at the so-called aerobic threshold is below 2 per mill. Even at maximum physical exertion, the contribution of anaerobic glucose degradation to lactate is certainly less than 2% of the additional energy provided! For more on the causes of the lactate increase see here.

So away with all the lactate nonsense? Not at all. The lactate thresholds have proven to be very helpful for training control. You shouldn’t get rid of them, but you should interpret them differently.

more detailed: The importance of lactate

There is every indication that lactate has an important signaling function: a slight increase triggers a wide variety of effects: from the formation of new blood vessels (angioneogenesis) not only in the stressed muscle to the assumption that the positive effect of physical activity on brain function is even caused by lactate receptors in the brain. Lactate is the most important source of energy for the heart during strenuous exercise. It is burned in the heart using oxygen.

So get moving, the higher the lactate, the better for the brain? Certainly not!

Quote from the Süddeutsche Zeitung of 14.1.17: “In the finish area of a cross-country skiing competition, it sounds like a hospital ward. When the skiers have finished their race, the big coughing begins. Asthmatic problems are widespread in endurance sports, especially in winter.”

a case report:

In the early 1980s, reports on the positive effects of sport and the problems of obesity increased considerably. The number of “public runs” increased rapidly. “Running training” for those interested only took place very rarely. This was also the case at a 7 km fun run in Amberg, in which smaller groups also took part. This included a group of seven men aged between 20 and thirty who set off in temperatures well above 30°C. Two of them crossed the finish line, the others were found collapsed by the wayside and taken to hospital. Three were immediately admitted to intensive care. One of them was only found after a long search in the bushes. Completely dehydrated, pulse no longer palpable, requiring artificial respiration and dialysis for a week. The liver values were approx. 1000 times higher, the CK (a muscle enzyme that can also originate from the heart muscles) above the measuring range of the method, the pH value at 7.1! (from a pH of 7.35 one speaks of acidosis!), the lactate > 20 mmol/l! The man was in our intensive care unit for 7 days. He had not suffered any obvious, permanent damage. If he had arrived at the hospital a little later, he would probably not have had a chance.

From such incidents, which unfortunately did not only occur in Amberg, the appropriate precautionary measures have been derived; emergency helpers are positioned along the routes and in particular recommendations are given by the organizers to prepare sensibly for the planned run, to train for it!!!

Extensive research into lactate by sports scientists has shown that high lactate values above _LT2, the second lactate threshold, indicate the onset of acidosis in the body with all the associated problems.

We are therefore looking for a target corridor for a reasonable lactate increase. As always:

It’s the dose that counts, even with exercise!

What is meant by lactate thresholds?

Interestingly, the organism does not wait until the oxygen supply has already become very scarce. Depending on the level of training, increased anoxidative glycolysis (increased lactate formation) already begins when the untrained person has reached around 30 % of the maximum oxygen consumption capacity and the well-trained person around 50 %. In this situation, there is an increase in lactate in the blood. The amount of lactate produced increases exponentially with further increases in exertion. If the lactic acid can initially still be buffered by the various buffer systems – I will devote a special chapter to the bicarbonate buffer – acidosis will increasingly develop at lactate values above 3 – 4 mmol lactate/l. The organism and in particular the working muscles become acidic, which ultimately leads to a drop in performance.

While a low increase in lactate is seen as favorable, as a mediator of training success and many other positive effects of exercise, high lactate values are associated with negative effects, but are often unavoidable in competition if you want to be among the winners.

The concept of lactate thresholds was born out of these considerations. The lactate thresholds are specified as the heart rate at which a defined lactate value has been reached.(On different lactate threshold concepts).

LT1₍ the 1st lactate threshold) is defined below as the heart rate at which the first reliably measurable increase in lactate is seen (0.2 mmol above the lowest measured value). According to Dickhut and others_, LT2 is the heart rate at which the lactate concentration in the blood is 1.5 mmol lactate/l higher than the lactate at _LT1.

As you can see from the figure below, you have to interpolate the heart rates at the defined lactate concentrations from the figure. there are various programs available for this purpose, including commercially available ones. Alternatively, you can evaluate the lactate curve yourself as described in the chapter: Technique for determining lactate thresholds .

We have found the use of a typical Excel file with xy representation of the parameters (heart rate as x-axis) to be effective. We use the heart rate as the x-axis because we want to determine the heart rate at which it is reasonable to train. If LT1_{and LT2} are represented as a line in the diagram, the corresponding heart rates can be easily read off by inserting a rectangle whose sides pass through the intersection points of the lactate curve with the thresholds. However, you can also download the diagram free of charge from our download page free of charge.

LT2 is often interpreted to mean that from this lactate concentration onwards, the outflow of lactic acid into other tissues can no longer be increased, so that the lactate concentration rises continuously from this point onwards and the organism becomes acidic (MaxLass concept). However, this assumes that higher lactate concentrations do not result in higher lactate degradation.

The term “individual anaerobic threshold” (IANS) is often used for the term “_LT2“. This implies that from this point onwards, a significant proportion of the energy supply comes from the anaerobic metabolism. As described in the chapter: Where does lactate come from and how large is its contribution to energy production, even at maximum exertion, less than 2% of the additional energy required is produced anaerobically, i.e. without the use of oxygen. The statement sometimes made that from this point onwards the metabolism is completely anaerobic is completely nonsensical! What then happens to all the oxygen whose consumption reaches its maximum at maximum capacity (VO2max)?

Why are we concerned with lactate thresholds? On the one hand, it is now assumed that_a training effect worth mentioning only comes about with an increase in lactate from LT1, and that most of the positive effects of sport are mediated by an increase in lactate – today we even talk about the lactate hormone, which makes an endocrinologist particularly interested in this substance! On the other hand, a prolonged, pronounced increase in lactate above _LT2 is associated with negative effects. This leads to the development of acidosis, hyperacidity and other negative effects. For example, cortisol increases in the blood, which ultimately promotes the breakdown of amino acids to glucose in the working muscle cell; counterproductive in efforts to build muscle! For the consequences of overloading in the Covid era, see here.

The lactate thresholds are therefore of central importance for recommending the heart rate at which you should train.

We recommend that recreational and health athletes start training at a heart rate between _LT1 and _LT2.
To increase the heart rate as training progresses, see Adjusting the training heart rate