Physical Endurance and Its Specific Differentiation

Фотографии: 

A.M. Trofimov, associate professor, Ph.D.
A.I. Prokof’ev, associate professor, Ph.D.
Bunin Yelets State University, Yelets, Russia

Key words: general endurance, special endurance, aerobic, anaerobic, glycolysis, oxidative phosphorylation.

Modern theory of physical education postulates the existence of some types of physical endurance, namely general and special, anaerobic and aerobic.

Zh.K. Kholodov and V.S. Kuznetsov interpret general endurance as an ability to do work of moderate intensity for a long time in the process of global functioning of muscular system [4]. According to the textbook “Theory and Methods of Physical Education” edited by B.A. Ashmarin, general endurance is a long execution of work with optimal functioning activity of main life-supporting organs and organism’s structure. [1]

We can see that the first definition gives a more specific idea about the defined phenomenon, namely it says about the work of moderate intensity. In comparison with it the second definition appears to be rather abstract. In particular, it is not clear what the author is speaking about using the term “optimal functional activity”. Trying to give a concrete definition the author adds that such an activity manifests itself in the process of doing exercises in the zone of moderate loads.

Apart from the abovementioned definition, Zh.K. Kholodov and V.S. Kuznetsov call the general endurance aerobic [4], meaning that in the process of doing the work that does not presuppose considerable muscular strain the main source of a renewal of adenosine triphosphate (ATP) is the reaction of oxidative phosphorylation of adenosine diphosphate (ADP), requiring oxygen.

One can ask a question – why should we judge general endurance taking into consideration an ability to work under conditions of moderate strain? As though answering this question, the authors cite as an example running at a moderate rate saying that a person who is able to run for a long time will be able to swim, ride a bicycle and do some other things for a long time too [4]. It is necessary to admit that it is a rather controversial statement.

As it seems to us, the essence of the notion of general endurance as well as a criterion of its evaluation must be a certain integrated result, shown by an individual in different kinds of activity requiring endurance. Moreover, it happens not only in such types of activity where muscles work with moderate intensity.

The criteria of general endurance evaluation are specified in the modern literature on the theory of physical education. They suggest taking the result of a six- or twelve-minute running as a measure of general endurance. But it is none other than determination of endurance in some specific kind of activity, i.e. special endurance in middle-distance races. In this connection, it is necessary to call 3,000- and 5,000-meters runners the most enduring ones, because a second-ranked runner in one of these competitions will win a victory over any master of sport in swimming, rowing, football, cycling and so on. It is natural that this situation can’t be called normal.

It is impossible to determine a person’s general endurance level by the method of multi-event testing, therefore, the only way which is also sufficiently objective to evaluate this quality remains the measurement of possibilities of oxygen transporting system and more precisely the measurement of the level of maximum oxygen consumption per kilogram of an individual weight. The point is that a person with a more trained oxygen transporting system will have an advantage over his rival in most cases when the question is about competitions in non-core activities requiring physical endurance.

There is an opinion that general endurance is the basis of special endurance, in this connection some exercises presupposing its development are used in the training process in a number of kinds of sport. First of all, they offer to run cross-country distances and the longer they are, the better. After questioning some coaches why they make their athletes run we found out that in their opinion running for a long time had a favorable effect upon their breathing. For example, breathing more freely during a boxing match gives an athlete an opportunity to box under more comfortable conditions.

Thus, we can ascertain that the purpose of running in those cases is to improve the work of oxygen transporting system and nothing more. But the improvement of oxygen transporting system takes place when you are engaged in any kind of activity connected with muscular strains which are rather long and intensive including the ones in the process of doing competing exercises. Moreover, the result of endurance training in that case is not only training of oxygen transporting system and the systems that utilize it but also doing competing exercises causes sounder learning of doing these movements. Using a series of sparring matches in the training process gives athletes a chance to work at some other components of competing training besides training of endurance.

Non-core exercises can become necessary only if the conditions of his trainings don’t enable athlete to make his oxygen transporting system work hard in the process of doing competing exercises.

This scenario of training has nothing in common with training of general endurance meaning the way it must be carried out. It ought to be a multi-event training involving doing a great number of various moving actions with different intensity (not only moderate but also high). But this scenario of trainings is unacceptable for a person who specializes in a certain kind of activity.

As we have already mentioned, modern theory and physiology of physical education differentiate all manifestations of physical endurance into two types: aerobic and anaerobic endurance. In conformity with it, the purpose of endurance training in one case is to develop anaerobic abilities, in the other case, to develop aerobic ones. The reason for this differentiation is the statement that there is not practically such an element of power-provision of muscle contractions as oxidative phosphorylation of ADP in the process of doing exercises with maximum capacity and close to it. The reason for the absence of this reaction can be inertness of processes of transporting oxygen to muscles. [3] According to the opinions of different authors, the intensity of oxidative phosphorylation becomes maximum only one-two minutes after the beginning of the work. But the research done by us gives cause to doubt it showing the opposite.

As it is known, the condition of the beginning of oxidative phosphorylation in mitochondria is the presence of oxygen, ADP, pyruvic acid in a muscular cell. ADP appears in a cell since the moment of the first reaction of hydrolysis of ATP. Its concentration increases as the concentration of kreatine phosphate decreases. The supply of the latter is not big. And if practically at the same time with the reaction of resynthesis of ATP by kreatine phosphate other reactions of power-provision were not developed, the force of muscular contractions gradually decreasing would come to nought during some seconds. But it doesn’t happen because glycolysis begins to make its contribution to power-reproduction, at the same time with the renewal of ATP, giving molecules of pyruvic acid to mitochondria. Another component of oxidative phosphorylation is oxygen that initially is in a muscular cell as a part of myoglobin.

The fact that all these necessary components are available for the reactions of oxidative phosphorylation predetermines their beginning. As kreatine phosphate decreases and the content of ADP increases, glycolysis and oxidative phosphorylation gain force. After a few seconds of contractions these reactions fully replace resynthesis of ATP by kreatine phosphate.

As oxygen contained in muscle fibers decreases, they begin to get it from the blood. As the volume of carbon dioxide coming into the blood increases, the breath and the frequency of heart contractions quicken. After ten seconds of hard work of a great number of muscles (e.g. in the process of squatting with an almost maximum weight) the intensity of pulmonary ventilation and the frequency of heart contractions are becoming maximum.

In this connection, it is possible to state that the contribution of aerobic component to the processes of power-provision of intensive muscular contractions lasting even a few seconds is rather great.

The main reason for the idea about the possibility of moving activity in the particularly anaerobic mode is the fact that its authors have forgotten for some reason about the oxygen stored up by muscle fibers and constantly present in the blood. They took values of pulmonary ventilation for the whole period of work as a criterion of assessing aerobic component in power-reproduction in the process of carrying out intensive brief physical actions. It’s natural that this value turned out small because breath frequency becomes maximum not from the starting line but gradually when carbon dioxide comes into the blood and oxygen leaves it.

It’s possible to mention another reason giving ground to have an opinion about gradual increase of productivity of oxidative phosphorylation in the process of work. This is statement of the fact that oxygen consumption really increases gradually in those cases when the question is about the work in the mode of compensated tiredness. Gradual increase of muscle fibers involved by volitional efforts in work predetermines the gradual growth of requirement for oxygen and that of requirement for removal of carbon dioxide. Thus, here we deal not with inertness of the development of oxygen transporting processes but with absence of maximum requirement for it at first.

Parts of aerobic and anaerobic phosphorylation of ATP in the process of work are determined by the volume of mitochondria and productivity of glycolysis of working muscles. Productivity of glycolysis in many respects is determined by the structure of fibers involved in work. The more fast fibers work, the more part of anaerobic power-provision is. Therefore, in the process of working with maximum capacity when maximum volume of fast muscle fibers is made to function, the part of glycolysis in power-provision appears to be the largest. At the same time the part of glycolysis is determined by the whole structure of working muscles and the purposefulness of their training. A weightlifter’s part of glycolysis will be considerably bigger than a skier’s one in the process of doing the same work. This circumstance gave another reason for not noticing aerobic contribution to the common process of power-provision of muscular contractions of maximum capacity.

As it is known, training of endurance by means of doing exercises of high power capacity makes for the growth of glycolysis productivity. But it doesn’t become its only result and it is far from being its main purpose. Contribution of oxidative phosphorylation of ADP increases even more, and the following facts prove it. Firstly, this is a rather considerable growth of oxygen consumption by athletes going in for different kinds of sprint. It is natural that the whole increase is used to provide the growing requirements of mitochondria of trained muscles. In this connection, the growth of oxygen consumption could be bigger but for the peculiarities of training of this kind. In particular, if it concerns the brief time of the training work itself as compared to the training work of athletes preparing for long distance running. Under these conditions all departments of oxygen transporting system don’t get such development that takes place in the latter case.

Secondly, it turns out to be impossible to provide a considerable growth of glycolysis without the increase of aerobic component in the processes of power-reproduction. The point is that the activity of glycolysis ferments depends on pH sarcoplasm. [3] As the productivity of glycolysis increases and muscle fibers inevitably becomes more acid, then it is pointless to speak about the possibility of the essential growth of resynthesis of ATP due to glycolysis if there are no conditions for utilization of pyruvic acid and hydrogen. The only possible solution to this problem is activation of aerobic processes. The higher productivity of mitochondria is, the more hydrogen is utilized and the more possibilities exist for glycolysis.

As it is known, the full oxidation of two molecules of pyruvic acid and four hydrogen atoms allows to reproduce eighteen times more molecules of ATP than in the process of splitting of one molecule of glucose into two molecules of pyruvic acid and four molecules of hydrogen. In this connection, we can make a conclusion that the growth of glycolysis productivity is followed by a considerable increase of productivity of mitochondria.

Thus, we can state that it doesn’t matter what exercises an athlete uses to trains endurance, the main contribution to the improvement of result is made by the growth of aerobic component of the processes of power-provision. Therefore, it is wrong to speak about aerobic and anaerobic endurance as independent phenomena and more than that, to speak about training of each of them in particular. Differentiation of all manifestations of endurance can take place only concerning types of activity and the zones of intensity of performed exercises.

References

  1. Ashmarin, B.A. Theory and Methods of Physical Education: textbook for students of physical education departments. / B.A. Ashmarin, Yu.A. Vinogradov, Z.N. Vyatkin, edited by B.A. Ashmarin. – Moscow: Prosveschenie, 1990. – 287 P.  (In Russian)
  2. Dubrovsky, V.I. Physiology of Physical Education and Sport. / V.I. Dubrovsky, V.N. Smirnov. – Moscow: Vlados, 2002. – 255 P. (In Russian)
  3. Mikhaylov, S.S. Sport Biochemistry. Text: textbook for higher education institutions and colleges of physical education. / S.S. Mikhaylov. – 4th edition, stereotyp. – Moscow: Sovetsky Sport, 2007. – 260 P. (In Russian)
  4. Kholodov, Zh.K. Theory and Methods of Physical Education and Sport: textbook for students of higher education institutions. / Zh.K. Kholodov, V.S. Kuznetsov. – 5th edition, stereotyp. – Moscow: Academia, 2007. – 480 P. (In Russian)