Dr.Biol., Professor R.V. Tambovtseva¹
I.A. Nikulina^1
1Russian State University of Physical Education, Sports, Youth and Tourism (SCOLIPE), Moscow

Keywords: track athletes, hormones, metabolic substrates, insulin, glucagon, unesterified fatty acids, somatotropin, glycerine.       

Background. There is currently a fairly large number of works on the hormonal dynamics under physical loads [1-3]. Such peptide hormones as insulin, somatotropin, and glucagon are known to be crucial in mobilizing the energy resources of the human body [3-5]. The study of the dynamics of exercise-related changes in the plasma hormone concentrations in active elite athletes and those retired from elite sports can be of great relevance for assessing the sports performance and health status of elite athletes.

Objective of the study was to identify the dynamics of the substrate and hormonal changes in highly-skilled athletes specializing in middle-distance running and former track athletes.

Methods and structure of the study. The experiment under the study was run in the Muscular Activity Bioenergy Research Laboratory of the N.I. Volkov Sports Biochemistry and Bioenergy Department of Russian State University of Physical Education, Sports, Youth and Tourism. Sampled for the experiment were the active (n=12) and retired (n=10) athletes specializing in middle-distance running. The subjects were apparently healthy and after a doctor’s permission gave their informed consent to participate in the experiment. The active and former athletes performed the same load – a standard exercise stress test to failure. The test lasted from 12 to 15 minutes. The subjects’ heart rate and gas exchange parameters were recorded at rest, during the test and during the first 10 minutes of recovery. In addition, venous blood samples were drawn at rest, at the moment of failure, and during the 3rd and 10th minutes of recovery to determine the insulin, somatotropin, glucose, glycerine, and unesterified fatty acids concentrations. We measured the lactic acid concentrations in the capillary blood and catecholamines and their precursors in the urine. The radioimmunoassay and fluorometric methods were applied.

Results and discussion. The study data and analyses showed that during the exercise stress test to failure, the volume of the workload performed by the former athletes was on average 148.4+4.56 kg-m/kg and that the average duration of their work was 10.4+0.23 minutes, while in the group of active athletes, the workload volume was 275.5+8.34 kg-m/kg and the average work duration was 14.91+0.32 minutes. There were statistically significant differences between the active and former athletes in terms of several physiological indicators (see Table 1).

Table 1. Dynamics of oxygen metabolism values in active and retired elite athletes, M+m

It is shown that the values of oxygen demand, oxygen supply, maximal oxygen consumption, maximal oxygen pulse, and maximum ventilatory equivalent for oxygen in the active athletes were statistically significantly higher than in the former athletes.

The results obtained when analyzing the dynamics of changes in the hormone and energy substrate concentrations in the active and former athletes in the initial state, immediately after the test, showed that the insulin level at rest was slightly lower in the active athletes than in those who had retired from elite sports. At the same time, the glucagon concentration was higher in the active athletes, but the differences were insignificant. Except for the glycerine level, no significant differences were found between the two groups of athletes when measuring the metabolic substrate concentrations. The glycerine concentration in the active athletes was lower than in the former ones (p<0.05).

At the moment of failure to perform an exercise further, the insulin level decreased in both groups, while the concentrations of somatotropin, unesterified fatty acids, glycerine, glucose and glucagon increased. The insulin level in the active athletes was lower than in those who had retired from elite sports. There was a significant increase in the somatotropin and glucagon concentrations. When analyzing the individual characteristics of hormones and metabolites, the former athletes were found to have a greater individual variation than the active athletes. For example, some retired athletes were found to have the glucagon concentration increased, while in others it decreased. The post-load glucose concentration in the active athletes increased significantly versus the baseline. In both groups, there was a significant increase in the unesterified fatty acids and glycerine concentrations as compared to the baseline data, but the intergroup differences were insignificant.

The identified dynamics of changes in the hormone and metabolic substrate concentrations during the recovery period were as follows. During the 3rd minute of recovery, the insulin, somatotropin and unesterified fatty acid levels were higher in the active athletes than in the former ones (p<0.05). In terms of other parameters, the differences detected during the 3rd minute of recovery were insignificant. By the 10th minute of recovery, the blood insulin of the active athletes remained higher as compared to those retired from elite sports. The somatotropin level was also higher in the active athletes (p<0.05). The unesterified fatty acids level during the 3rd minute of recovery decreased in the group of active athletes, while in the group of former athletes it increased.

Therefore, it can be said that the results obtained during the study indicated the activation of the somatotropin and glucagon secretion in response to the physical load in both groups. This activation was more pronounced in the active athletes. The physiological significance of this reaction seems to lie in the hormone-induced mobilization of the energy substrates from fat and liver depots to ensure the working muscles’ demand. Since the metabolic substrate level results from completely different processes of their mobilization, it is fair to say that the speed of one process prevails over the speed of another. During the exercise stress test to failure, the rate of mobilization of unesterified fatty acids, glucose and glycerine was higher than the rate of their utilization, which was reflected in the increased concentration of metabolic substrates in response to the exercise. Along with the activation of the somatotropin and glucagon secretion, the mobilization of energy substrates is aided by the decrease in the insulin level associated with the suppression of the secretory activity of the β-cells of the pancreas and enhancement of the receptor binding of this hormone in the working muscles. The decreased insulin secretion may also be due to the activation of the sympathoadrenal system under physical loads, and this process was observed in both study groups.

The data obtained indicated that such metabolic reactions as activation of lipolysis, glycogenolysis, and other catabolic processes are associated with increased glucagon- and somatotropin-producing cell activity. It can be assumed that the effects of somatotropin and glucagon on the metabolic processes occurring under exercise are accompanied by a sufficiently wide range of catabolic hormones - the hormones of the anterior pituitary lobe, cortex of the adrenal glands, and catecholamines. At the same time, the withdrawal of one of the regulatory links can be compensated by the activation of other links. Increasing physical load to failure breaks the pattern of decrease in the training process of the amplitude of hormonal shifts in response to the exercise of constant power and duration. Extreme loads require the mobilization of all body reserves, and in this case, the physical fitness level may be expressed in the maximal activation of all the hormonal regulation systems. Conspicuous is the fact that in terms of economization, the hormonal system of the athletes who have retired from sports is, in a way, approaching that of people who have never been into sports.

Conclusions. The values of oxygen demand, oxygen supply, maximal oxygen consumption, maximal oxygen pulse, and maximum ventilatory equivalent for oxygen in response to physical loads were significantly higher in the active athletes than in the former ones. Under the influence of dosed physical loads, the somatotropin secretion increased in both study groups. This activation was most pronounced in the active track athletes, which was associated with the hormone-induced mobilization of the energy substrates from fat and liver depots to ensure the working muscles’ demand. Extreme loads require all reserves of the body being mobilized. Moreover, the physical fitness level is expressed in the maximal activation of all the systems of hormonal regulation.

References

1. Kraemer W.J. Rogol A.D. The endocrine system, sport and physical activity. Kiev: Olimpiyskaya literatura, 2005, 599 p.
2. S.V. Pogodina, Aleksanyantz G.D.  Adaptive changes in glucocorticoid activity in elite athletes of different sex and age groups. Teoriya i praktika fiz. kultury. 2016. No. 9. pp. 49-52.
3. Tambovtseva R.V., Nikulina I.A. Changes in hormonal regulation of metabolic processed in speed skaters in different phases of training cycle. Teoriya i praktika fiz. kultury, 2015, No. 5, pp. 52-54.
4. Tambovtseva R.V., Nikulina I.A. Specifics of hormonal regulation of energy metabolism in athletes in various disciplines when training to failure. Teoriya i praktika fiz. kultury, 2016, no. 1, pp. 28-30.
5. Fisher D.A. The Quest diagnostics manual. Endocrinology test selection an interpretation, 4^th ed. San Juan Capistrano, CA: Quest Diagnostics Nichols Institute, 2007. 369 p.

Corresponding author: ritta7@mail.ru

Abstract

Objective of the present study was to identify the dynamics of the substrate and hormonal changes in highly-skilled athletes specializing in middle-distance running and former track athletes.

Methods and structure of the study. This study involved the highly-skilled athletes specializing in track and field athletics, middle-distance running, and former track athletes, who had retired from elite sports. They were subject to an exercise stress test to muscular failure. The physiological and biochemical measurements were taken.

Results of the study and conclusions. It was found that the response of the hormone system to physical loads in the athletes who had retired from elite sports differed from that in the active athletes. Adaptation to physical loads was not maintained in the retired athletes. The effects of somatotropin and glucagon on the metabolic processes under physical loads were found to be accompanied by the activity of a sufficiently wide range of catabolic hormones - the hormones of the anterior pituitary lobe, cortex of the adrenal glands, and catecholamines.