Often, the validity of lactate diagnostics is underestimated and spiroergometry overestimated in the current discussion on performance diagnostics in endurance sports. As so often, the truth is in the middle of this topic!
Also read the first part of the article: Performance diagnostics in endurance sports
Spiroergometry does a lot, but, like the lactate concentration, it is subject to different influencing factors, so that the uncritical use here contains just as much potential for error as the lactate diagnostics. An intelligent performance diagnostics often depends on the stage model used, the experience of the diagnostician and the interpretation of the collected data.
Spiroergometry is used not only in cardiology and pneumology but also in the performance diagnostics of endurance-trained athletes. In the science of training and sports medicine, it is on the one hand to the objective presentation of cardiopulmonary performance, on the other hand, but also to derive training areas.
Threshold is not equal threshold!
When deriving the training areas during endurance training and when determining the maximum possible intensity over longer periods, the recognition of a so-called steady state is important. This is often equated with the individual anaerobic threshold (IAS) in lactate diagnostics. Also in spiroergometry an anaerobic threshold is determined, which should not be equated with the IAS! (1) Rather, there are different areas in the metabolism: While the anaerobic threshold of lactate diagnostics describes an area in the muscle metabolism in which lactate buildup and Balancing lactate degradation, the anaerobic threshold in spirometry describes an altered situation in the respiratory economy. In the area of the anaerobic threshold of spiroergometry, the respiratory equivalency also rises with increasing load. This describes that your body now has to ventilate more air with increasing load to absorb 1 liter of oxygen. The two thresholds carry the same name, but describe different points in the load metabolism. When carrying out a spiroergometry without lactate measurement, the training areas must therefore be determined under different conditions than in a joint performance of a step test with determination of the lactate kinetics and the measurement of the respiratory gases.
Search for the threshold
Apart from the question of whether "the" threshold can exist at all, since the transitions of the physiological parameters are rather to be seen as a fluid transition, it must be confusing that there are numerous threshold models. This is often attributed to lactate diagnostics as a "disadvantage", whereby it is ignored that models for determining a threshold were often developed under sport-specific questions or for certain step-testing procedures. The mere presence of different methods for determining a threshold as a point of criticism is therefore inadmissible. In addition, the anaerobic threshold in spiroergometry can also be determined by various methods.
In addition to the method described above for measuring the increase in the respiratory equivalent, there is another method: In the so-called V-Slope method, a regression analysis of carbon dioxide Abathmung (VCO2) for oxygen uptake (VO2) is calculated to the range of excess CO2 production to investigate. This increase in carbon dioxide emissions occurs through the buffering of the hydrogen ions (H + ions), which are produced by buffering the acidic environment with bicarbonate. (1, 2) In addition, the respiratory compensation point can be determined in a spiroergometry Increasing non-metabolic carbon dioxide arises. This shows the area in which your metabolism takes place in a very acidic environment - this area is above the IAS from the lactate measurement.
Determine the training areas
When it comes to setting the target zones in training, current measurement methods should help to attribute to the training areas how the energy at the center of gravity is provided by the body. In the basic area 1 (GA1) z. B. essentially the aerobic energy supply from fats and carbohydrates are addressed, while in the basic endurance area 2 (GA2) increasingly also the anaerobic energy supply plays a role. The thresholds described above should now help to be able to distinguish the training areas from each other. It is important to make sure that the division of the training areas around the "thresholds" is quite dependent on the type of sport and the distance. Thus, it must be determined for each athlete, depending on the sport and for the different disciplines, how the training areas are to be divided. It makes a difference how long a long-distance triathlete can maintain its performance at the individually determined threshold or a triathlete that starts on the Olympic distance. Experienced trainers and diagnosticians work here with their own concepts.
The misconception of being able to measure lipid metabolism
In the meantime, suppliers of "spiro-merger devices" are targeting the fitness and health market, with the aim of being able to measure fat metabolism under stress. These devices record the oxygen consumption and the CO2-Abatmung. Using the so-called indirect calorimetry is to be concluded on the energy consumption and the energy supply from fats and carbohydrates. Equations for glucose oxidation or for β-oxidation (fat burning) from the ratio of these two quantities, the so-called respiratory quotient, should determine how the energy supply is distributed. However, the various existing algorithms provide very different results. (3) Basically, measuring oxygen and carbon dioxide to determine fat burning or carbohydrate combustion, however, provides barely usable data. The reason for this is that, as the proportion of anaerobic glycolysis increases - ie the burning of carbohydrates without oxygen - carbon dioxide is released that does not come from the energy metabolism. This non-metabolic CO2 is released from the bicarbonate buffers and already dilutes the results in the area of the first lactate increase. Falsification of results can already be expected at low intensities.
Showbusiness instead of science
Determining the proportion of your fat burning under stress is more like clever marketing than serious science. However, you must be warned against uncritical deployment. Not least because of the mentioned influence variables, training areas can not be determined by a supposedly measured fat metabolism. The training areas determined with such systems can often not even be transferred to training practice. As an athlete, be warned against false prophets who, under the guise of reputable measurement methods such as spiromergometry, try to determine areas of training for fat and carbohydrate metabolism.
Performance diagnostics provide a wealth of insights, with lactate and spiroergometry combined for comprehensive results. The criticisms often made of the lactate level test appear to be based on commercial interests rather than on serious scientific analysis. With spiroergometry, make sure that the thresholds and lactate thresholds determined in the respiratory gas measurement are sufficiently explained to you. Endurance athletes have the opportunity to review their training adjustments and to adapt their training to the results. However, blanket recommendations for evaluation based on lactate diagnostics or spiroergometry can not be given. The evaluation of each individual athlete requires intuition and knowledge of the physiological processes in the body! Especially the complexity of the energy-providing systems and their constant interaction show how sensitively the human body reacts. It is even more important that you learn to question results. Indirect calorimetry, ie the depiction of fat and carbohydrate combustion, is scientifically untenable and must be questioned in a performance diagnostic evaluation! Both lactate level testing and spiroergomerism are influenced by variables and confounding variables. You should therefore always be carried out by an experienced sports scientist or sports physician. In the comparison of both methods none can be classified as "better" or "superior" - the respective question determines the method to be used!
1. European Journal of Applied Physiology, 2003, Vol. 89, p. 281-288.
2nd German Journal of Sports Medicine, 2011, Vol. 62 (1), pp. 10-15.
3rd International Journal of Sports Medicine, 2005, Vol. 26, pp. 28-37.