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Publication date: 01.03.2023
DOI: 10.51871/2782-6570_2023_02_01_1
UDC 573.2
FEATURES OF SEASONAL BIORHYTHMS ASSOСIATED WITH THE CARDIOVASCULAR SYSTEM FUNCTION IN FIRST-YEAR STUDENTS
I.S. Kal‘berdin, A.N. Inyushkin
Samara University, Samara, Russia
Annotation. Despite a significant amount of empirical data on the influence of circadian rhythms on the functional systems of the human body, the role of seasonal rhythms has not been studied enough, in our opinion. The purpose of this work was to identify the features of seasonal biorhythms associated with functions of the cardiovascular system of first-year students. The results obtained show significant seasonal fluctuations of the cardiovascular system’s indicators, which indicates a need to consider these indicators in the arrangement of the educational process for the studied group.
Keywords: biorhythms, zeitgebers, adaptive potential.
Introduction. At the current moment, big chronological data has been gathered on the features of the rhythmic organization of the physiological systems of the human and animal body. The physiological systems of mammals (nervous, cardiovascular, respiratory, digestive, excretory, reproductive) are characterized by a presence of a great number of circadian, ultradian and infradian biorhythms interacting with each other [1]. The most studied ones are the circadian (comes from the Latin: circa – approximately, and dies – day), physiological, biochemical and behavioral rhythms. It is known, that the main circadian oscillator that sets biorhythms to organs and functional systems of the body, including structures of the central nervous system, is located in the suprachiasmatic nucleus [2].
A modern man often does not consider many rhythm-based factors of nature, such as sunlight, circadian, seasonal and other zeitgebers, although the endogenic biorhythm program is embedded in the genetic code. Desynchronization of biorhythms and external geophysical and social rhythm-based factors may lead to dysfunctions of regulatory physiological mechanisms of the body, consequently – to disorders and pathological dysfunctions [3].
The purpose of this study: to reveal the features of seasonal biorhythms associated with the cardiovascular system’s function in first-year students.
Methods and organization. The study of seasonal biorhythms has its own complications due to the fact that it is very difficult to organize standard measurements of the functional state and set strict time frames for them.
The studies included 44 male students aged 18-20 years, who studied in the Samara University in 2020-2022. The control testing took place during the first year of study (2020-2021), the experimental testing – during the second year (2021-2022). The authors have chosen the common testing methods: heart rate monitoring and blood pressure measurement (sBP – systolic blood pressure, mm of Hg; dBP – diastolic blood pressure, mm of Hg).
Evaluation of the cardiovascular system’s reducing properties was made with the Rufier Functional Test, which was calculated according to the formula:
where Р1 – heart rate (HR) at rest for 15 s; Р2 – HR for 15 s after physical activity (30 squats for 1 minute); Р3 – HR for 15 s of the first minute of recovery.
Evaluation of the heart reducing properties: RT<0 – excellent work of the heart; 0 to 5.0 – very good work of the heart; 5.1-10.0 – good; 10.1-15.0 – moderate; >15 – poor.
The autonomic tone assessment was carried out with the Kerdo index (KI) according to the formula:
where dBP – diastolic blood pressure, mm of Hg; HR – heart rate, beats/min.
The KI assessment: KI>0 – the sympathetic influence prevails, KI<0 – the parasympathetic influence prevails.
The integral indicator of the adaptive potential (AP) was calculated with the Baevskij’s formula:
AP=0.011×HR+0.012×sBP+0.008×dBP+0.14×age–0.009×mbody–0.009×Hbody–0.27,
where HR – heart rate, beats/min; sBP – systolic blood pressure, mm of Hg; dBP – diastolic blood pressure, mm of Hg; mbody – body mass, kg; Hbody – body height, cm; age, years.
The results are interpreted as follows: AP less than 2 – satisfactory adaptation level; 2.1 to 3.0 – adaptation strain; 4.1 and higher – adaptation failure [4].
The results were statistically processed with the SigmaPlot 12.5 software package. The arithmetic mean indicators of HR, RT and AP are presented as arithmetic means (M) ± standard errors of mean (δ). With the SigmaPlot 12.5 software, we evaluated the distribution law of examined indicators with the Shapiro-Wilk test. Since values of most registered indicators did not correspond with the law, the next statistical data processing used the ANOVA Post-hoc test (Bonferroni t-test). The significance level was identified with the Student's T-test during the winter (1), spring (2), summer (3) seasons of the first year and the autumn (4) season of the second year. Values were deemed as critical if р≤0,05.
Results and discussion. While analyzing dynamics of biorhythmic characteristics in students, we took into the account the fact that the exam period is connected to the season change (winter and spring exams), which is why in order to reduce errors in measurements we registered the indicators during the period between exams in daytime at the specified time intervals (10:00-14:00): winter (January-February), spring (April-May), summer – after summer exams (from mid-June to July), autumn (October-November) seasons [5].
The data obtained is presented in the table below.
Table
Dynamics of the cardiovascular system’s indicators in first-year students during different seasons of the year
|
Seasons |
Winter |
Spring |
Summer |
Autumn |
|||||
|
Parameters |
М |
δ |
М |
δ |
М |
δ |
М |
δ |
|
|
HR, beats/min |
Control |
89.97 |
11.76 |
84.75 |
9.31 |
81.66 |
12.00 |
75.07 |
7.22 |
|
Experim. |
90.31 |
10.3 |
85.3 |
8.24 |
82.56 |
12.00 |
75.44 |
6.07 |
|
|
sBP, mm of Hg |
Control |
132.89 |
8.25 |
129.72 |
8.84 |
127.06 |
9.60 |
123.79 |
5.92 |
|
Experim. |
129.5 |
5.34 |
126.7 |
7.21 |
126.0 |
6.61 |
123.8 |
3.2 |
|
|
dBP, mm of Hg |
Control |
80.56 |
7.01 |
76.30 |
4.41 |
72.10 |
7.59 |
75.26 |
4.96 |
|
Experim. |
78.16 |
6.91 |
74.45 |
4.33 |
71.08 |
5.52 |
74.26 |
4.22 |
|
|
PP, mm of Hg |
Control |
13.93 |
3.78 |
12.25 |
3.69 |
11.65 |
4.06 |
9.62 |
4.03 |
|
Experim. |
12.22 |
3.88 |
11.06 |
3.23 |
10.85 |
3.86 |
8.52 |
3.83 |
|
|
KI, c.u. |
Control |
8.65 |
11.05 |
7.95 |
10.77 |
9.86 |
10.51 |
-1.26 |
8.96 |
|
Experim. |
7.22 |
9.05 |
6.99 |
8.98 |
7.54 |
9.71 |
-1.54 |
3.25 |
|
|
AP, c.u. |
Control |
0.93 |
0.22 |
0.62 |
0.38 |
0.69 |
0.25 |
0.64 |
0.13 |
|
Experim. |
1.47 |
0.30 |
0.55 |
0.19 |
0.50 |
0.17 |
0.44 |
1.00 |
|
Note: HR – heart rate; sBP – systolic blood pressure; dBP – diastolic blood pressure; PP – pulse pressure; KI – Kerdo index; AP – adaptive potential
HR is a very variable indicator that is sensitive to external and internal factors. The revealed tachycardia has become the most common type of functional deviation, especially during our first examination. The decrease in the tachycardia values by the end of the year shows a tendency for normalizing the heart activity, and, in our opinion, it occurred due to internal factors (fig. 1).
Fig. 1. Heart rate dynamics in students during different seasons (p<0.01)
The examined students had higher values of blood pressure during the winter season, which was characterized by the systolic and diastolic hypertension. By the first exam period of the 2nd year, the blood pressure indicators of most students were within the standard values.
The Kerdo index is considered as an important characteristic describing the state of the cardiovascular system. It is also traditionally used as an indicator of the ratio of the sympathetic and parasympathetic nervous system tone. Since the heart work and vascular tone depend on autonomic regulating sympathetic and parasympathetic influences, the Kerdo index was used for a seasonal evaluation of the cardiovascular system. Negative values show a prevalence of the parasympathetic influence on blood circulation, positive values – prevalence of the sympathetic influence [6].
The conducted research revealed that the autonomic balance in all groups during winter-spring and spring-autumn periods shifted towards sympathetic activity (KI increased), and during summer-autumn period – towards parasympathetic activity (p<0.01) (fig. 2).
Fig. 2. Kerdo index and pulse pressure dynamics (М±δ) in students during different seasons
Note: above – control measurement results, below – experimental measurement results
We have also found significant correlations (p<0.01) in sBP and dBP between seasons according to the Student’s T-test, which is shown in the figure 3.
Fig. 3 Correlations between the Kerdo index indicators according to the Student’s T-test in the control and experimental measurements
Note: bold lines – pronounced direct connections (r=0.35–0.69)
Functional strain of the cardiovascular system revealed after the Rufier test is shown in other indicators, the adaptive capabilities of students in particular. The comprehensive criterion reflecting these capabilities (AP) is based on the systemic approach and, in our case, it was calculated as an integrative indicator that includes age and morphofunctional features of the students. These features are shown in the table above and they demonstrate that a student’s body does not experience complications associated with adaptation to the learning process.
Conclusion. The experiment that took 2 years with a fairly homogenous group of students allowed identifying significant seasonal fluctuations of the cardiovascular system indicators, which shows the need to take them into account in the educational process organization for the studied group.
REFERENCES
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- Inyushkin A.N., Petrova A.A. Circadian phase shifting of wheel running and modulation of spike activity in the rat suprachiasmatic nucleus by neuropeptide Y. Circadian Rhythms and Their Importance, p. 161-194.
- Wittmann M., Dinich J., Merrow M., Roenneberg T. Social jetlag: Misalignment of biological and social time. Int, 2006, vol. 23, issue 1-2, pp. 497-509.
- Baevskij R.M., Berseneva A.P. Evaluation of the adaptive capacity of the body and the risk of developing diseases. Moscow: Meditsina, 1997. 236 p. (in Russ.)
- Kal’berdin I.S. Features of the dynamics of physiological indicators characterizing the adaptive capabilities of first-year students depending on infradian (seasonal) biorhythms. Youth and Modern Science: International Interdisciplinary Scientific and Practical Conference, 2021. pp. 30-37. (in Russ.)
- Kerdo I. An index calculated from blood circulation data to assess the vegetative tonus situation. Acta Neurovegetat, 1966, vol. 29, pp. 250-268.
INFORMATION ABOUT THE AUTHORS:
Igor’ Sergeevich Kal’berdin – Post-Graduate Student, Samara University, Samara, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Aleksej Nikolaevich Inyushkin – Doctor of Biological Sciences, Professor, Head of the Department of Human and Animal Physiology, Samara University, Samara, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
For citation: Kal’berdin I.S., Inyushkin A.N. Features of seasonal biorhythms associated with the cardiovascular system function in first-year students. Russian Journal of Sports Science: Medicine, Physiology, Training, 2023, vol. 2, no. 1. DOI: 10.51871/2782-6570_2023_02_01_1