{"id":8504,"date":"2020-11-15T13:54:20","date_gmt":"2020-11-15T12:54:20","guid":{"rendered":"https:\/\/profheinen.de\/8436-2\/fat-burning-pulse\/"},"modified":"2025-04-30T11:43:03","modified_gmt":"2025-04-30T09:43:03","slug":"fat-burning-pulse","status":"publish","type":"page","link":"https:\/\/profheinen.de\/en\/diagnostics\/spiroergometry\/fat-burning-pulse\/","title":{"rendered":"Fat burning pulse"},"content":{"rendered":"\t\t
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Fat burning does not stop during intensive physical exertion<\/h2>
<\/div>

According to a publication: Lotz, Heinen, St\u00f6cker, Beyer, Heinen; 2019<\/a><\/p>

Anyone who talks about the optimum fat-burning pulse has not been paying attention to biochemistry!<\/h2>

The ratio of exhaledCO2<\/sub> and inhaled O2<\/sub> (the respiratory quotient) can be used in spiroergometry to determine how much glucose or fatty acids contribute to energy production, at least at rest. ( seeIndirect calorimetry<\/a> ) <\/p>

A typical example of the course of the respiratory quotient (more correctly: the expiratory exchange rate; RER) under a gradual load (increase in load by 40 watts every 4 minutes) until exhaustion is shown in Fig. 1. <\/p>

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Fig 1: Progression of the RER in 8 soccer players under a gradual increase in load of 40 W \/ 4 minutes until exhaustion. The lactate thresholds<\/a> were used to assess the exercise intensity.<\/figcaption><\/figure>
Initially, the RER often drops slightly(effect of the decrease in hyperventilation<\/a> at the start of the unaccustomed exercise test), but then it rises as soon as the lactate concentration in the blood becomes measurably higher. It almost always reaches values of > 1 at maximum exercise, which theoretically cannot be the case! <\/span><\/div>
<\/div>

As shown in the chapter on indirect calorimetry<\/a>, the calorie consumption can be calculated from the oxygen consumption using the so-called caloric equivalent of an average of 4.85 Kcal \/ l of oxygen consumed. The caloric equivalent changes slightly depending on the RER, i.e. whether more glucose or fatty acids are used to provide energy. The corresponding formula can be found here<\/a>. In the following data, the caloric equivalent is adjusted to the corresponding RER. <\/p>

Table 1 shows how many calories the 8 footballers consumed on average during the increasing load and how many of the calories are produced from the oxidation of fatty acids or glucose, assuming that all of theCO2<\/sub> in the exhaled air comes from the combustion process. See Table 2<\/a> for the respective VCO2<\/sub> and VO2<\/sub> values. <\/p>

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Table 1: Calculation of calories from the oxidation of fatty acids or glucose during graded spiroergometry in 8 soccer players using the uncorrected RER (respiratory exchange rate).<\/figcaption><\/figure>

Fig. 2 shows the proportion of fat oxidation and glucose oxidation under the above assumptions for the different exercise levels of our test group. <\/p>

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Fig. 2: Calorie consumption from fat (yellow) and glucose (blue) during the different exercise levels in the 8 soccer players studied using the RER values shown in Fig. 1.<\/figcaption><\/figure>

At this point you can see a typical picture that has led to the statement that during intensive physical exertion, not only in percentage terms, but also in absolute terms, fewer and fewer fatty acids contribute to energy production, and that at maximum exertion only glucose is oxidized. At the same time, the glucose should be broken down into lactate with an extremely low degree of efficiency. Which unconvincing engineer has come up with something like this? <\/p>

No, not badly constructed,
incorrectly described!<\/span><\/strong><\/h2><\/div>

One of the protagonists who made a huge contribution to spiroergometry, Wasserman, pointed out in his work in 1964 that the RER should only be used as a measure of the proportion of fatty acids and glucose in oxidation if no other source of exhaledCO2<\/sub> was available.<\/p>

However, Wasserman et al. showed in 1973<\/a> that bicarbonate decreases with the increase in lactate in the blood with increasing exercise – a finding that we also recorded in our footballers, but which can also be seen in every spiroergometry test in which a blood gas analysis is carried out at the same time. As an example, we show the data from our examination of the 8 soccer players in Fig. 3:<\/p>

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Lactate and Bicarbonate During a Graded Exercise Test<\/figcaption><\/figure>

Unfortunately, Wasserman and the many other researchers who have made the same claim have failed to calculate how large the proportion of exhaledCO2<\/sub> is due to the buffering of lactate. As a result, the theory that the amount ofCO2<\/sub> in the exhaled air resulting from the drop in bicarbonate is negligible has prevailed. The aim of our study was to investigate how many mlCO2\/minute<\/sub> result from the buffering of lactate by bicarbonate at higher loads. <\/p>

Calculation of the proportion of buffering in the exhalation ofCO2<\/sub> at higher physical exertion.<\/h3>

(This task should be easily solvable by a student in the advanced chemistry course!)<\/p>