PhD, Associate Professor S.V. Pogodina¹
Professor, Dr.Med. G.D. Aleksanyantz^2
1V.I. Vernadsky Crimean Federal University, Simferopol, Republic of Crimea, Russia
²Kuban State University of Physical Culture, Sport and Tourism, Krasnodar, Russia

Keywords: glucocorticoid function activity, category of elite athletes, sex and age differentiation, glucocorticoid response range, compensatory and adaptive capabilities.

Introduction. An in-depth study of the adaptive features of reactivity of the stress-realizing systems in the trained body requires a methodological approach based on the sex and age differentiation of the category of elite athletes [2]. This differentiation actualizes the following contradiction. On the one hand, the body of elite athletes exhibits the optimal, acquired as a result of long-term adaptation, characteristics of reactivity of the main physiological systems that are responsible for the adaptation of the body and its fatigue resistance [3, 4]. On the other hand, the threshold load conditions in certain sex and age groups can determine the degree of tension of the mechanisms of self-regulation and compensation of the homeostatic functions [7], an increase or decrease in the reactivity of the neurohormonal adaptation among them [6]. Herewith, great importance is attached to the mechanism of activation of the adrenal cortex producing cortisol - the hormone, which has a pronounced ergotropic effect [1].

Compensatory changes in the activity of the adrenal cortex, that are necessary to meet the metabolic requirements and are only possible in case of coordinated activity of the regulatory nerve centers, allow to maintain the desired level of working productivity [5]. In this view, the study of the adaptive changes in the glucocorticoid activity in elite athletes, in the context of the sex and age differentiation, provides additional physiological characteristics of reactivity of the stress-realizing system and enables to allocate the groups demonstrating the compensatory mechanism tension at the level of hormonal adaptation to certain threshold loads.

The research objective was to study the adaptive changes in the glucocorticoid activity in elite athletes of different sex and age groups.

Research methods and organization. We examined elite male athletes in the preadult (17-21 years, n=123), early (22-34 years, n=82) and middle (35-46 years, n=86) adulthood, who were engaged in sports with primarily cyclic training loads, aimed at development of their aerobic and strength endurance ("endurance" and "strength" groups, respectively). The control age groups were made of apparently healthy untrained males, who had been subjected to a medical examination (n=195). Within the "endurance" group we examined the subgroups of elite female athletes with ovulatory (ovarian) menstrual cycle (OMC), (16-26 years, n=32) and anovulatory menstrual cycle (AMC), (37-45 years, n=18). The female athletes had a regular menstrual cycle and did not take any birth control pills. The cortisol and estradiol levels in the blood serum were measured by means of the enzyme-linked immunosorbent assay using SteroidIFA-Cortisol-01 (CJSC "Alkor Bio", Russia) and Estradiol ELISA (The Calbiotech, Inc (CBI), USA) kits. The reference values were as follows: 10-370 pg/ml ​​for estradiol, 150-760 nmol/l for cortisol. Ovulation was detected using the immunoassay OVUPLAN LUX. The hormone levels in the female athletes were measured in different days of their menstrual cycle (MC) during menstruation (1-3 days); in the intermenstrual period (8th-9th, 20th-22th days); in the ovulatory period (13th-16th days); in the premenstrual period (26th-27th days). The hormonal tests were taken in the initial condition and during the step test on the Kettler ergometer bike. Step load was performed at the pedaling speed of 60 rpm for 3-4 minutes and was of low (W₁=100-120 W), moderate (W₂=150-180 W) and submaximal (W₃=200-250 W) intensity. Heart rate at the level of the low, moderate and submaximal load intensity was equal to 130-140, 150-160, 170-180 bpm, respectively. The pulmonary ventilation rate was measured using spiro-pneumotachometry by means of the "Spirobank - G" device (Italy), and was corrected to the BTPS conditions. Expiratory oxygen pressure (P_EO₂, mmHg) was determined using the thermochemical oxygen gas indicator "Shchit-3'' (Ukraine) and was corrected to the STPD conditions. The oxygen consumption index was detected using the calculation method (VO₂, ml/min). All the indicators under study were recorded for 30 seconds at the end of the last minute of each load stage. The results were processed using the parametric and nonparametric methods of mathematical statistics using the software OriginPro 8.5.1. The statistically significant differences were determined using the Student t-criterion, Wilcoxon t-criterion. P<0.05 was taken as a statistically significant difference. The observations were made during the retractive mesocycles in the preparatory period of the training process on a voluntary informed consent basis.

Results and discussion. The groups of elite male athletes and untrained males were observed to have the significant differences in the cortisol levels (Me [min; max]) at the level of moderate (W₂) and submaximal (W₃) load intensity. In adolescence (preadult period), an increase in the load intensity at the corresponding load stages did not cause any rise of the cortisol blood levels in the "endurance" and "strength" groups. The group of untrained males had a significant decrease in the glucocorticoid activity at submaximal load intensity (cortisol at rest - 360.70 [141.00; 401.20], cortisol W₃ – 305.95 [135.10; 372.00], p=0.0023). In the early adulthood period, increasing cortisol levels in the "endurance" group were detected during submaximal loads (cortisol at rest - 413.00 [365.43; 1113.15], cortisol W₃ – 514.70 [174.10; 1662.65], p=0.0065), whereas in the "strength" group increasing cortisol levels were registered as early as during the moderate-intensity loads (cortisol at rest - 425.00 [374.65; 1364.05], cortisol W₂ – 478.60 [213.00, 364.05], p=0.0495). In both "endurance" and "strength" groups, cortisol production in the body of elite athletes in the middle adulthood period increased during the moderate-intensity exercise. At the same time, in the "strength" group, an increase in the load intensity up to the submaximal level led to an increase in the cortisol production (cortisol at rest - 521.16 [417.17; 1085.32], cortisol W₂ – 674.50 [518.34; 778.82], p=0.00235, cortisol W₃ – 841.00 [533.86; 1003.21], p=0.00004), whereas in the "endurance" group an increase in the cortisol production was not recorded at the given load stage (cortisol at rest – 448.00 [424.00; 588.60], cortisol W₂ – 546.50 [447.90; 823.70], p=0.00001, cortisol W₃ – 539.50 [440.00; 852.16 ], p=0.96367). The untrained individuals in the middle adulthood period showed a decrease in the cortisol levels with an increase in the load intensity (cortisol at rest – 504.00 [352.00; 709.30] cortisol W₂ – 427.10 [351.50; 695.90], p=0.00026, cortisol W₃ – 362.00 [337.50; 673.20], p=0.00001). We also studied the range of the glucocorticoid activity, based on the statistical value of interquartile range (IQR), which reflects cortisol deviations in the body in 50% of the cases. It was found that the IQR value in the groups of elite male athletes and untrained males in the preadult and middle adulthood periods was significantly lower as compared to the first adulthood. In the groups of elite male athletes in the preadult and middle adulthood periods the peculiarities of the glucocorticoid response range manifest themselves depending on specific characteristics of long-term adaptation. The "endurance" group is distinguished by the narrow glucocorticoid response range at the moderate and submaximal load intensity levels (IQR cortisol (nmol/l) adolescence - W₂ – 96.30, W₃ – 112.70; middle adulthood - W₂ – 83.50, W₃ – 96.00) as compared to the "strength" group (IQR cortisol (nmol/l) adolescence - W₂ – 136.60, W₃ – 348.80; middle adulthood - W₂ – 192.00, W₃ – 200.00). This indicates the limited adaptation level of glucocorticoids and its relative stability in the "endurance" group. A relatively wide range of the glucocorticoid response in the "strength" group is, obviously, due to a greater demand in the diversity of the response pattern in certain directions resulting from the effects of the intense strength component of physical work. The group of untrained males demonstrated a relatively small glucocorticoid activity range due to the absence of the adaptation basis that forms a certain response potential.

The dynamics of the glucocorticoid response was compared to the dynamics of VO₂ (s±Sx) at different levels of load intensity. It was established that in the body of elite adolescent male athletes of the "endurance" group, oxygen demand during moderate and submaximal exercises was significantly lower compared to the "strength" group (VO₂, ml·min^-1 "endurance" adolescent males W₂ – 2607.94±40.24, p<0.001, W3 – 2963.99±48.9, p<0.001; "strength" adolescent males W₂ – 3320.52 ± 23.71, W3 – 4109.54±29.4). Oxygen demand in the "endurance" group during the submaximal loads increased significantly in the early adulthood period rather than in the preadult one (VO₂, ml·min^-1 at W₂, early adulthood W₂ 4784.77±35.80, adolescence - 2963.99±48.9, p<0.001). While in the "strength" group there was no significant increase in oxygen demand in the early adulthood period compared to the preadult one (VO₂, ml·min^-1 at W₂ during early adulthood – 4273.46±14.90, in preadult period – 4109.54±29.4, p>0.05). However, the dynamics of oxygen consumption in the "endurance" and "strength" early adulthood groups has a linear dependence on the increasing load intensity. In the middle adulthood period the oxygen demand rate increases in the "endurance" groups during submaximal exercises, but the VO₂ value is significantly lower compared to early adulthood. In the "strength" group oxygen demand during moderate and submaximal exercises is equal (VO₂, ml·min^-1 at W₂ -1958.22±15.65, W₃ – 2002.21±23.21, p> 0.05), that is, there is an upward trend in the VO₂ levels during submaximal loads in this group of elite athletes. The untrained athletes had a significant increase in oxygen demand when performing low-intensity exercises (VO₂ exceeds the level of athletes), especially in adolescence and in early adulthood, which indicates the reaction redundancy. In middle adulthood the oxygen consumption is relatively limited during moderate and especially submaximal exercises (VO₂, ml·min^-1 at W₂ – 1467.19±29.32, at W₃ – 1900.65±27.67). The analysis of the glucocorticoid activity features in the body of elite female athletes revealed the hyperergic cortisol responses during loads of various intensity in the dynamics of OMC and AMC (Table 1).

Table 1. Pattern of changes in the cortisol and estradiol levels in elite athletes (significant increase - ↑, significant decrease - ↓)

Note: significant differences are shown relative to the baseline.

The hyperergic cortisol responses under low-intensity exercises were observed in the premenstrual period in the dynamics of OMC, and during menstruation in the dynamics of AMC. Additionally, as compared to elite female athletes with AMC, those with OMC demonstrated a mix of steroidogenesis in response to loads. At the same time, physical loads performed in the second half of the MC stimulated an increase in estrogenic steroidogenesis in female athletes with OMC, whereas female athletes with AMC, on the contrary, were distinguished by primarily decreased steroidogenetic activity. In addition, we detected relative tolerance of estradiol responses to loads in female athletes with AMC and tolerance of cortisol responses in female athletes with OMC. The analysis of the ranges of glucocorticoid activity in the body of elite female athletes revealed their pronounced narrowing in the dynamics of AMC as related to those with OMC (IQR cortisol (nmol/l) OMC min - 150, max - 500; AMC min - 25, max - 140). Oxygen demand in all the study groups increased significantly with an increase in the load intensity. Meanwhile, we noticed that oxygen demand in the body of elite female athletes increased significantly by the period of ovulation, i.e. by the 13th-16h day from the beginning of the MC (VO₂, ml· min^-1 at W₂ – 1942.12±17.24, W3 – 3140.08±14.79, p<0.05). At the same time, estrogen levels in elite female athletes with OMC reached the values typical of the ovulatory peak by this period (103.8 [90.00, 183.3] pg/ml). While estrogen levels in the body of elite female athletes with AMC did not exceed theses values by the 13th-16th day of the MC (93.4 [83.0; 97.5] pg/ml, p=0.00338), and the degree of oxygen demand was significantly higher as compared to elite female athletes with OMC (VO₂, ml·min^-1 at W₂ – 2000.96±17.43, W₃ – 3398.37±17.10, p<0.05).

Obviously, oxygen demand in elite female athletes was mostly dependent on the function cyclicity, which is formed at the level of generative relations between the central nervous and endocrine systems and affects the ventilatory function [8].

Conclusions.

1. The sex and age differentiation of the category of elite athletes revealed a number of additional adaptive features of the glucocorticoid activity in the trained body.

2. The maximum value in the range, as well as the hyperergic pattern of the glucocorticoid response, were registered in elite male athletes in the early adulthood period. The range narrowed in the preadult and middle adulthood periods, which was manifested to a greater extent in the "endurance" group.

3. The compliance of the direction of the glucocorticoid response with the metabolic request is observed in early adulthood. In adolescence, there is a glucocorticoid response delay in the "strength" group. In the middle adulthood period, during the submaximal loads, an insufficient glucocorticoid response was observed in the "endurance" group and a compensatory reserve of this response in the "strength" group.

4. Elite female athletes were distinguished by mostly hypoergic glucocorticoid responses. In the dynamics of OMC, there was a relatively wide range of glucocorticoid responses, which improves the compensatory and adaptive capabilities within the system of steroidogenesis.

References

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Abstract. The research objective was to study the adaptive changes in the glucocorticoid activity in elite athletes of different sex and age groups. We examined elite male and female athletes in their preadult, early and middle adulthood periods, who were engaged in sports with primarily cyclic training loads, aimed at the development of their aerobic and strength endurance (the "endurance" and "strength" groups). The level of steroid hormones, ventilation and gas exchange rates were studied using the immunological, spiropneumotachometric and thermochemical methods, cycloergometric test with the gradually increasing intensity. Having applied the methodological approach related to the differentiation of elite athletes into the sex and age groups, we were able to expand the concept of ​​the glucocorticoid activity in the trained body. We have detected the differences in the kinetics and range of the glucocorticoid response. This range narrows in elite male athletes in the preadult and middle adulthood periods, which is manifested in a greater degree in the "endurance" group. In adolescence, there is a glucocorticoid response delay in the "strength" group. In middle adulthood, during the submaximal loads, an insufficient glucocorticoid response was observed in the "endurance" group and a compensatory reserve of the response in the "strength" group. In the dynamics of anovulatory and ovulatory (ovarian) menstrual cycles we mostly detected hypoergic glucocorticoid responses. In the dynamics of ovulatory menstrual cycle there was a relatively wide range of glucocorticoid responses.