PhD, Associate Professor E.A. Biryukova¹
PhD, Associate Professor D.R. Khusainov¹
Senior teacher N.P. Mishin¹
Dr. Biol., Associate Professor S.V. Pogodina¹
Dr. Biol., Professor E.N. Chuyan^1
1Vernadsky Crimean Federal University, Simferopol
²Kuban State University of Physical Culture, Sports and Tourism, Krasnodar

Corresponding author: sveta_pogodina@mail.ru

Abstract

Objective of the study was to identify the physiological features of the mechanisms to compensate for the shifts in the acid-base balance and cation-anion homeostasis in skilled orienteering athletes under competitive loads.

Methods and structure of the study. The in vivo and in vitro tests included the measurements of the main functional parameters of the skilled orienteering athletes (heart rate, maximum oxygen consumption), as well as the biochemical indicators of the acid-base balance and ion concentration of the blood (lactate and creatinine rates, concentrations of the hydrogen, chlorine, carbonic acid, sodium, potassium, and calcium ions). The study was conducted with the use of the hardware and software complex for gas analysis of the exhaled air, Epoc reader and Epoc host blood analysis systems, and lactate analyzer. Also, the integral indicators (anionic gaps) were calculated and the Davenport nomogram was constructed.

Results and conclusions. The study found that competitive loads lead to the development of increased-anion gap metabolic acidosis in skilled orienteering athletes, with respiratory alkalosis being the main compensatory mechanism. Moreover, the base excess (BE-ecf, BE-b) and anion gap (Agap, AgapK) rates serve as the informative markers of shifts in the acid-base balance both in the cluster and individual analyses. The pH rates obtained during the cluster analysis had a low informative value.

Keywords: physiological features, compensatory processes, metabolic shifts, acid-base balance, blood ion concentration, competitive loads, skilled orienteering athletes.

Background. Within the unit of biochemical reserves providing for metabolism under the influence of physical loads, the leading role is assigned to the markers of the acid-base balance and cation-anion contents [3], namely, lactate and creatinine rates, partial pressure of carbon dioxide and oxygen in the mixed venous blood, concentrations of the chlorine, carbonic acid, sodium, potassium, calcium, and hydrogen ions, capacity of buffer bases [4, 5]. The study of the above markers in the orienteering athletes under high-intensity competitive loads becomes highly topical and acquires practical importance in terms of the biochemical monitoring and diagnostics of fatigue at the level of the shifts in the acid-base and ionic homeostasis. In turn, the analysis of the metabolic shifts in the orienteering athletes in the field makes it possible to predict compensatory reserves, adjust the volume and intensity of physical loads to improve their functional fitness in the competitive periods of the year-round training [1, 2].

Objective of the study was to identify the physiological features of the mechanisms to compensate for the shifts in the acid-base balance and cation-anion homeostasis in skilled orienteering athletes under competitive loads.

Methods and structure of the study. Sampled for the study were 8 skilled orienteering athletes (Masters of Sport in foot orienteering) who gave their voluntary written informed consent to participate in the experiment. Oxygen consumption (VO₂) rates at the competitive stages were determined on a calculated basis. For this purpose, prior to the field studies, the athletes were subjected to a PWC₁₇₀ cycle ergometer test, in which the maximum oxygen consumption (VO₂max, ml³ min^-1), relative VO₂max (ml·min^-1/kg), and maximum HR (HR_max, bpm^-1) were determined using the Biopack (USA) hardware-software complex for gas analysis of the exhaled air. Further on, actual VO₂ and % VO₂max at the competitive distance were determined based on their percentage ratio of individual VO₂max and HR_max. The economical efficiency of the circulatory system was evaluated b calculating the oxygen pulse rate (OP, ml·beats^-1 =VO₂/HR) [6]. The blood lactate content at the competitive distance was measured in the finger prick test using the lactometer Lactate Plus (USA) and Lactate Plus - Test Strips (USA), and disposable lancets Safety (Austria). The biochemical blood parameters were recorded using Epoc reader and Epoc host (Canada). Mixed venous blood samples were taken from the finger using the specialized capillary tube Epoc (Canada) 3 minutes before the start of the competition and immediately after passing the competitive distance (4.7 km, 16 control points, total ascent - 225 m, average speed of passing the distance (V, m/s) - 9.09 1.02 m/s, average time of passing the distance: group of athletes - 43.02±0.06 min, leader - 38.13 min). The blood biochemical data was registered with the use of the Epoc reader and Epoc host blood analysis systems (Canada). The blood sample was entered into a special test card 30 seconds after the draw. The following blood parameters were measured: creatinine content (Crea, mg/dL), chlorine ion concentration (Cl^-, mmol/L), carbonic acid ion concentration (cHCO₃^-, AB, mmol/L), sodium ion concentration (N⁺, mmol/L), potassium ion concentration (K⁺, mmol/L), calcium ion concentration (Ca⁺⁺, mmol/L), hydrogen ion concentration (pH), buffer base capacity (BE-ecf, BE-b, mmol/L), partial pressure of carbon dioxide and oxygen in the mixed venous blood (pCO₂ and pO₂, mmHg, respectively). The anion gap (mmol/L) was calculated by the formula (Agap=[Na+]-([HCO3-]+[Cl-]), the anion gap with potassium (mmol/L) – (AgapK=([Na+]+[K+]) ([HCO3-]+[Cl-]). The obtained numerical data were processed using the STATISTICA 10.0 software package. We calculated the mean value and error o arithmetic mean. The study was supported by Grant No. AAAA-A20-120012090164-8 from FSAEI HE V.I. Vernadsky Crimean Federal University.

Results and discussion. The study found that under competitive loads, HR, VO₂, VO₂max, La, and OP (p<0.05) in the orienteering athletes increased statistically significantly as early as at the first stage of the distance, and slightly increased at the second and third stages (p<0.05), which indicated a high adaptation level of the body, realization of its functional reserves under high-intensity physical loads, as confirmed by the stable speed of running when passing the distance. The study showed that at the end of the distance, pCO₂ in venous blood decreased from 41.3±0.83 mmHg (baseline) to 37.2±1.81 mmHg, p<0.01, and apO₂ increased from 71.7±2.46 mmHg (baseline) to 82.1±2.16 mmHg, p<0.05.

The analysis of the ion concentrations after the competition revealed that Cl^- and HCO₃^- changed statistically significantly. Thus, the concentration of Cl^- increased from 105.1±0.53 (baseline) to 108.2±0.66 mmol/L (p<0.05) and that of cHCO₃^-  decreased from 25.4±0.42 (baseline) to 21.2±1.53 mmol/L (p<0.05). Besides, after the competition, the N⁺ concentration increased from 141.5±0.68 (baseline) to 143.1±0.5 mmol/L (p<0.05) and that of K⁺ increased even more significantly - from 4.4±0.19 (baseline) to 5.7±0.27 mmol/L (p<0.05). The integrative indicators of the cation-anion ratio are Agap and AgapK (Fig. 1). At the end of the competitive distance, Agap increased from 10.7±0.26 (baseline) to 15.8±1.33 mmol/L (p<0.05) and AgapK increased from 15.1±0.43 (baseline) to 21.4±1.32 mmol/L (p<0.05).

Fig. 1. Changes in base excess (deficiency) and anion gap rates before (base) and after competitive loads

According to the data obtained earlier [6], the normal range for Agap is 7-14 mmol/L, for AgapK - 10-18 mmol/L, hence, there takes place an increase in the anion gap and overrange in both cases. In addition, the most important integrative indicators of the acid-base balance are the standard (BE-ecf) and actual (BE-b) base excess (deficiency). In was found that BE-ecf and BE-b shifted towards the negative value at the end of the competitive distance: BE-ecf shifted from the extreme value – 2.3 – +2.2 to the range – 11.9 – +1.3 mmol/L, p<0.01, and BE-b - from – 2.1–+2.3 to -10,4 – +1,27 mmol/L, p<0.01.

Therefore, the athletes’ pCO₂ and pO₂ were within the normal range of the compensated values at the end of the competitive distance. While the changes in base excess and anion gap indicated the development of increased-anion gap metabolic acidosis.

Taking into account the physiological features of changes in the acid-base balance parameters, the identified acidosis was deemed metabolic and resultant from a buildup of lactic acid, though it manifested itself in 3 examined athletes only. In this view, it should be emphasized that it is precisely these athletes who were found to have the maximum negative shifts in BE-ecf and BE-b and the greatest anion gap; they underperformed at the competitive distance. Therefore, the analysis of the shifts in the acid-base balance and blood ion concentrations before and after the competition using H.W. Davenport nomogram [4], their association with the functional parameters in the field are of high practical importance in determining the vector of the compensatory processes providing for metabolic shifts, forecasting physiological features and competitive performance of skilled orienteering athletes.

Conclusions. The study found that competitive loads lead to the development of increased-anion gap metabolic acidosis in skilled orienteering athletes, with respiratory alkalosis being the main compensatory mechanism. Moreover, the base excess (BE-ecf, BE-b) and anion gap (Agap, AgapK) rates serve as the informative markers of shifts in the acid-base balance both in the cluster and individual analyses. The pH rates obtained during the cluster analysis had a low informative value.

References

1. Biryukova E.A., Pogodina S.V., Jeldubaeva E. R., Aleksanyants G.D. Biocontrol technologies to optimize motor-cognitive capabilities of orienteering athletes. Teoriya i praktika fiz. Kultury. 2020. No. 11. pp. 47-49.
2. Pogodina S.V., Yuferev V.S., Kryukov S.A. et al. Technologies of operative control of physical load and express-assessment of functional fitness of athletes at pre-competition stage. Fizicheskoe vospitanie i sportivnaya trenirovka. 2020. No. 1 (31). pp. 80-92.
3. Titlov A.Yu. Ratio between aerobic and anaerobic thresholds in qualified speedskaters. Teoriya i praktika fiz. kultury. 2021 no. 2. p. 36-40.
4. Davenport H.W. The ABC of Acid-Base Chemistry: The Elements of Physiological Blood-Gas Chemistry for Medical Students and Physicians. Chicago: The University of Chicago Press. 1974. 124 p.
5. Umeda A., Kawasaki K., Abe T., Yamane T., Okada Y. Effects of Hyperventilation on Venous-Arterial Bicarbonate Concentration Difference: A Possible Pitfall in Venous Blood Gas Analysis. International Journal of Clinical Medicine. 2014. No.5. pp. 76-80.