PhD I.V. Averyanova¹
PhD S.I. Vdovenko^1
1Research Center "Arctic" of the Far Eastern Branch of the Russian Academy of Sciences, Magadan
Keywords: young males, cycle ergometry, metabolism, cardiovascular system.

Background. Physical activity and health status are known to be strongly associated. Thus, the rise of the physical fitness level may have additional health benefits [5]. Physical load tolerance is currently used as a synonym for physical working capacity, which is now rated in the cycle ergometer test and is deemed to be the total physiological capacity of the body [3]. The ability to perform muscle work is among the most significant biological functions; it is determined based on the oxygen consumption rate and reflects the aerobic potential and physical working capacity of the body [1].

Objective of the study was to identify the impact of motor activity of young males on gas exchange, external respiration function, and cardiovascular system during the load testing.

Methods and structure of the study. Sampled for the study were the 17-21 year-old young males, permanent residents of the Magadan Region. All subjects were split into 2 groups based on their fitness level: Group 1 (n=36) – the average level of motor activity – young males engaged in physical training and sports activities under the academic physical education curriculum; Group 2 (n=32) – the high level of motor activity – young males having the sports qualifications of Candidate Masters of Sport and higher. The young males were subjected to a cycle ergometer test to be performed at the load power of 900 kg-m/min (150 W) and a constant pedaling speed of 60 rpm. Our earlier studies [2] showed that the load tolerance level can be determined in the 3rd minute of the cycle ergometer test, based on which we reduced the pedaling time to 3 minutes. The Medgraphics VO2000 metabolimeter (USA) was used to record the subjects’ heart rate, gas exchange and external respiration rates in a state of rest and in the 2nd and 3rd minutes of the cycle ergometer test.

The parametric data processing results are presented as a mean and an error in mean (M±m). The statistical significance of differences was determined using the Student t-test for dependent and independent samples. The research protocol was approved by the Bioethical Commission of the Federal Publicly Funded Institution "Science Institute of Biological Problems of the North of the Far Eastern Branch of the Russian Academy of Science" (No.001/019 of 29.03.2019).

Results and discussion. The analysis of the data obtained revealed that the young males from Group 1 had high values of heart rate, respiration rate, VE/VO₂, and VE/VCO₂ against the low oxygen utilization coefficient (O₂UC). The cycle ergometer test caused significant changes in gas exchange and external respiration function; however, the degree of changes depended on the load tolerance level. In the 2nd minute of testing, the number of significant differences went up: the study group with the moderate motor activity level had lower values of tidal volume, respiratory minute volume, VO₂, VE/VCO₂, which was observed against the higher respiratory quotient (RQ) and heart rate (HR).

Further load-specific changes in the 3rd minute of testing turned out to be even more significant. Thus, the young males from Group 2 were found to have lower values of heart rate, RQ, VCO₂, VE/VO₂, and FETO₂ against significantly higher values of VO₂, VE/VCO₂, and RQ. In the 3rd minute of testing, significantly higher O₂ and CO₂ concentrations in the exhaled air were characteristic of the subjects with the moderate level of motor activity.

At each stage of the cycle ergometer test, the heart rate values were lower in the group of young males with the high level of motor activity. The chronotropic load efficiency was 61.2% in Group 1 and 48% in Group 2. The data obtained showed a 28% increase in the chronotropic response in the study group with the moderate level of motor activity, which is deemed a display of inefficient cardiovascular system response to the workload (see Table 1).

Table 1. External respiration and gas exchange rates in healthy young males with average and high levels of motor activity

The figure illustrates the dynamics of changes in VCO₂ and VO₂ in the baseline and in the 2nd and 3rd minutes of the cycle ergometer test. It is known that the point of intersection of the VCO2 and VO2 curves are commonly referred to as a V-slope, where V-slope is the first point of departure from linearity of carbon dioxide output (VCO₂) plotted against oxygen uptake (VO₂) [6], which, according to the authors, is also associated with the start of the anaerobic metabolism and, hence, achievement of the anaerobic threshold. The figure illustrates that the point of intersection of the VCO₂ and VO₂ curves in the low load tolerance group was observed between the 2nd and 3rd minutes of testing, while in the high load tolerance group the VCO₂ and VO₂ curves did not intersect at all.

Direction of changes in ventilatory equivalent for oxygen and carbon dioxide in young males with different levels of physical load tolerance

Similar information on the achievement of the anaerobic (ventilatory) threshold can be obtained from the analysis of the dynamics of VE/VCO₂ and VE/VCO₂. In the works by foreign authors, an increase in VE/VO₂ without a corresponding increase in VE/VCO₂, which was typical of the young males with the average level of motor activity in the 3rd minute of testing, is considered to be the criterion for reaching the anaerobic threshold [6].

Thus, in the 3rd minute of testing, the young males with the average level of motor activity were characterized by higher values of FETCO₂ and FETO₂ as compared to those with the high level of load tolerance. The detected differences indicated that in Group 1, the changes in the capillary gas exchange were associated, on the one hand, with the decrease in the oxygen consumption, and on the other hand - with an increase in the metabolic carbon dioxide extraction at the ventilatory threshold. The test data showed that O₂UC was significantly lower in the subjects with the average level of motor activity. Given that the respiratory minute volume was virtually the same in both study groups, we may suggest an increase in oxygen diffusion between alveolar air and blood and an improvement in the oxygen transport function in the young males from Group 2, which was consistent with the statistically lower FETO₂ values in the 3rd minute of the cycle ergometer test.

Conclusions. The study data showed that throughout the experiment, the heart rate values were statistically higher in the young males from Group 1. Moreover, the chronotropic load efficiency testified to the increase in the heart rate response by 28%, which indicates uneconomic cardiovascular system functioning in response to the functional test. The young males from Group 2 were characterized by the high tidal volume rate, which provided the optimal level of pulmonary ventilation in the 2nd minute of testing: it exceeded that in the moderate motor activity group by 19%. Proceeding from the analysis of the dynamics of changes in the studied indicators, we may conclude that the moderate motor activity group of young males reached the anaerobic threshold between the 2nd and 3rd minutes of testing, while the high motor activity group never reached the anaerobic threshold.

References

1. Bukov Yu.A., Minina E.N. Comparative characteristics of adaptive reserves of respiratory system of 19-20 year-old females with different physical performance levels. Uchenye zapiski Tavricheskogo natsionalnogo universiteta im. V.I. Vernadskogo, Seriya «Biologiya, khimiya». 2011. v. 24 (63). No. 4. pp. 24-35.
2. Maksimov A.L., Averyanova I.V. Informative value of re-respiration test to assess resistance of young men’s body to combined action of hypoxia and hypercapnia]. Rossiyskiy fiziologicheskiy zhurnal im. I.M. Sechenova. 2017. v. 103, no. 9. pp. 1057-1068.
3. Balady G.J., Arena R., Sietsema K., Milani R. Clinician’s Guide to cardiopulmonary exercise testing in adults: a scientific statement from the American Heart Association. Circulation. 2010. V. 122. pp. 191-225.
4. Solberg G., Robstad B., Skjønsberg O.H. Respiratory gas exchange indices for estimating the anaerobic threshold. J. Sport Sci. Med. 2005. V 4. pp. 29-36.
5. Warburton D.E., Nicol C.W., Bredin S.S. Health benefits of physical activity: the evidence. CMAJ (Can. Med. Assoc. J.). 2006. V. 174. No. 6. pp. 801-809.
6. Wasserman K., Stringer W.W., Casaburi R., Koike A., Coop C.B. Determination of the anaerobic threshold by gas exchange. Biochemical considerations, methodology and physiological effects. Z Kardio. 1994. V. 83. pp. 1-12.

Corresponding author: vdovenko.sergei@yandex.ru

Abstract

Objective of the study was to identify the impact of motor activity of young males on gas exchange, external respiration function, and cardiovascular system during the load testing.

Methods and structure of the study. Sampled for the study were the 17-21 year-old young males, permanent residents of the Magadan Region, with different sports levels: usual (low load tolerance) and high (high load tolerance) motor activity modes. The Medgraphics VO2000 metabolimeter was used to record the subjects’ heart rate, gas exchange and external respiration rates in a state of rest and on the 2nd and 3rd minutes of the cycle ergometer test.

Results and conclusions. The analysis of the dynamics of changes in the respiratory coefficient, comparison of the oxygen consumption and carbon dioxide emission rates, as well as the ventilatory equivalent for oxygen and carbon dioxide in the average motor activity group, revealed that anaerobic (ventilatory) threshold was reached between the 2nd and 3rd minutes of testing, which was not observed in the high motor activity group of subjects during the cycle ergometer test.

It was found that a number of characteristics in the low load tolerance males indicated the inefficient cardiovascular functioning against the background of reduced oxygen consumption with high exhaled oxygen concentration, which was most evident at the peak of cycle ergometer test load. Such changes in the physiological systems of the body can be used as a prognostic criterion for assessing the level of physical fitness and training of young males during the 3-minute cycle ergometer test.