Steady State (Sports Science)

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As a steady state (English: steady : stet (strength), stable, consistent, state : Status, (supply) state) is called a steady physiological variables, such as lactate concentration in the blood , oxygen uptake or heart rate . This state can set itself at a significantly higher level during physical exertion and thus differs from homeostasis . The term Steady State was coined in 1924 by the English Nobel Prize winner Archibald Vivian Hill .

Lactate steady state

Lactate steady state is the equilibrium between the formation and breakdown of lactate during physical exertion. The lactate level in the blood should be between 1.5 and 4 mmol / l depending on the level of training  . This area is also called the aerobic-anaerobic transition area (AANÜ).

In a bicycle ergometer test, a steady state is set again after a short time after the increase to a higher load level, so that z. B. Muscle and blood lactate values ​​would not change after prolonged exposure at one level. The steady state can no longer be maintained until a high load level (e.g. 200 W) is reached, since the lactate formation increases significantly due to the increasing supply of energy through glycogenolysis . This leads to a continuous increase in lactate.

Maximum lactate steady state

The maximum lactate steady state ( maxLass or MLSS ) is the exercise intensity at which a lactate steady state is just established, i.e. an output can be kept constant over a period of 30 minutes and the blood lactate concentration over the last Increased by a maximum of 1 mmol / l for 20 minutes. The MLSS is characterized by the fact that, after a settling phase, the energy metabolism takes place aerobically in relation to the whole body, i.e. the lactate formed is either broken down oxidatively in the aerobic metabolism via pyruvate or built up into glucose .

With a load above the MLSS, the proportion of anaerobically lactic energy supply increases. This value therefore indicates the limit between purely aerobic and partially anaerobic energy supply. The MLSS thus corresponds to the anaerobic threshold . This does not mean that above the MLSS the additional energy required comes only from anaerobic lactic sources, since the oxygen uptake increases with increasing exercise.

The MLSS is around 60% of maximum oxygen intake for most people . Untrained people show a worse value, with very well endurance trained people reach values ​​around 80%. The lactate values ​​are on average around 4 mmol / l, whereby the value is independent of endurance performance and depends on other factors (see Lactate Shuttle ).

Determination of the MLSS

The exact determination of the MLSS requires a lot of effort. For example, after a first step test to roughly determine the exercise intensity, several 30-minute long-term tests with constant stress must be completed at intervals of two to three days. Depending on the lactate behavior during the continuous exercise, the intensity for the next run is slightly increased or reduced until a steady state is reached during the run. Due to the high level of effort, performance diagnostics attempt to determine performance using one of the various threshold concepts (e.g. individual anaerobic threshold).

meaning

Knowledge of the MLSS is important because exposure up to this threshold is essentially limited by the presence of glycogen . The energy production takes place on the threshold of aerobic-alactic to anaerobic-lactic acid. The decisive factor is the maximum oxygen absorption capacity in ml per minute per kilogram of body weight. The higher this value, the better the oxygen supply to the body works during exercise and the better the endurance level . Exposures above this threshold lead to a decrease in the glycolysis rate due to the increasing acidosis and thus to a premature termination of the exposure. However, the existence of such a threshold is questioned in the current scientific discussion.

Improvement of the MLSS

An improved MLSS is achieved, among other things, by:

  • optimized gas exchange in the lungs
  • sufficient number of red blood cells , which are responsible for transporting oxygen
  • Increase in the number of mitochondria
  • improved capillarization of the muscles
  • an improved ability of the liver and kidneys to break down lactate produced during performance
  • a well-developed fat metabolism
  • an economized heart activity that adapts faster to current energy requirements
  • an optimized movement sequence , whereby the (doctrinal) opinions about what is meant by an optimized movement sequence differ widely - only the degree of effectiveness is objectively measurable if the sporting discipline (e.g. cycling) compares the internal performance of the entire organism with the output effective for the advance is allowed at all.

The parameters listed are (among many others) improved by training in the areas of basic endurance 1 up to the intensity level called steady state. The individual steady state can be determined most precisely by analyzing the blood and breath values ​​during exercise. In addition to basic endurance training, other forms and means of training are also common and the subject of controversial discussions about the performance-enhancing effect of training.

criticism

The so-called threshold concepts are increasingly criticized for the fact that they cannot be justified physiologically. The energy supply processes in the body flow into one another so that there is no purely aerobic or anaerobic metabolism. This can be done e.g. For example, you can recognize that with every increase in competition length (e.g. from 10 km to 20 km run) the running speed decreases, regardless of whether you run above or below a certain threshold. The decrease in running speed is proportional to the running distance. Lactate is also no longer seen as a performance-limiting factor, so that performance diagnostics based only on lactate values ​​is questionable. In a special issue on the lactate problem, the editors stated in 2008 that “lactate thresholds as special points on the lactate performance curve are not more important for performance diagnostics and training control than other points on the curve. However, the fact that more than 30 years of focus on different threshold concepts may not really use the diagnostic potential of the lactate performance curve is not an argument to give up lactate-based performance diagnostics and training control. Rather, it indicates a considerable need for research ”. However, this also makes the training science theory that the focus of training must be on lactate tolerance extremely problematic.

Oxygen uptake

Excess post-exercise oxygen consumption.svg

The increase in oxygen uptake during physical exertion is delayed, so that a steady state of oxygen uptake does not occur until after about 2–6 minutes during submaximal exertion (see oxygen deficit ). The oxygen uptake then corresponds to the work intensity, which can be seen on the plateau in the graphic on the right. Conversely, after the end of an exercise, it takes a longer period of time (up to 38 hours) until the oxygen uptake has fully reached its resting value (see EPOC ). The decrease in oxygen uptake occurs almost exponentially.

Heart rate

The heart rate reaches a steady state after a short period of time when the load is below a certain continuous power limit and quickly falls back to the initial value after the load. At high loads, however, the heart rate no longer reaches a steady state, but increases continuously to a maximum with increasing load duration. After the end of the exercise, the heart rate returns to the starting value more slowly.

Metabolites and oxygen supply in the muscle

During muscle work , the increasing metabolite concentration (lactate, CO 2 ) causes the blood vessels to widen and thus the blood flow to increase . Due to the improved blood flow, the metabolites can be better transported away, so that a steady state is established between metabolite production and breakdown and the blood flow remains constant.

During long physical exertion (depending on the intensity from 30 minutes to several hours), the body has to do most of the work in steady state in order not to tire too quickly. An equilibrium between oxygen supply and oxygen consumption is established in the muscles .

Relative steady state

Relative steady state or sham steady state is a stress level in which oxygen uptake is constant, but pulse rate, ventilation and other parameters increase slowly.

See also

Individual evidence

  1. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 90
  2. ↑ Wildor Hollmann, Theodor Hettinger: Sports medicine. 4th edition, Schattauer, Stuttgart 2000, ISBN 3-7945-1672-9 , p. 333
  3. ↑ a b Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 313
  4. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 369
  5. ↑ Course book on spiroergometry . Thieme, Stuttgart 2010, ISBN 978-3-13-143442-5 , p. 209 .
  6. ↑ Oliver Faude, Wilfried Kindermann, Tim Meyer: Lactate Threshold Concepts. In: Sports Med 2009; 39 (6): 469-490
  7. ↑ Ricardo D. de Lucas, Naiandra Dittrich, Rubens B. Junior, Kristopher M. de Souza, Luiz Guilherme A. Guglielmo: Is the critical running speed related to the intermittent maximal lactate steady state? In: Journal of sports science and medicine (2012) 11, 89-94
  8. ↑ a b Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 374
  9. ↑ Wilfried Kindermann: Anaerobic threshold. In: German Journal for Sports Medicine , Volume 55, No. 6 (2004)
  10. ↑ a b Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 375
  11. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 463
  12. ↑ Kai Röcker: Dispute about the emperor's beard: Which lactate threshold is the best? In: German Journal for Sports Medicine Volume 59, No. 12 (2008)
  13. ↑ Benjamin Holfelder, Dieter Bubeck: Theoretical considerations about the training control based on the lactate metabolism and the muscle fiber typing. In: Swiss Journal for Sports Medicine and Sports Traumatology 60 (1), 32–39, 2012
  14. ↑ P. Wahl, W. Bloch, J. Mester: Modern ways of looking at lactate: Lactate an overestimated and at the same time underestimated molecule. In: Swiss Journal for Sports Medicine and Sports Traumatology 57 (3) / 2009, p. 104, online full text access (PDF; 206 kB)
  15. ^ Heck, H .; Benecke, R. (2008): 30 years of lactate thresholds - what remains to be done? In: German magazine for sports medicine 59 (12), 297-302.
  16. ↑ Arnd Krüger : Wrong theory? In: competitive sport 46 (2016) 2, pp. 14–15.
  17. ↑ a b Wildor Hollmann, Theodor Hettinger: Sports medicine. 4th edition, Schattauer, Stuttgart 2000, ISBN 3-7945-1672-9 , p. 69
  18. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , pp. 376-378, 505
  19. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , pp. 656-657
  20. ↑ Horst de Marées: Sports Physiology. 9th edition. Sportverlag Strauss, Cologne 2003, ISBN 978-3-939390-00-8 , p. 279