Features of Change of Students 'Heart Rate Variability Indicators under the Influence of Mental and Physical Load
Authors:   Petro Mohyla Black Sea National University, 10, 68 Desantnykiv St., Mykolaiv 54003, Ukraine, M. L. Kochyna , Bila A. A. , Bondarenko I. G. , Bondarenko O. V. 
Published: December 2020

The high level of mental and physical training loads on the body of students requires a good development of adaptive-compensatory mechanisms, stress resistance, psychological endurance. On the other hand, modern research indicates the low level of health of students and their maladaptation to high levels of stress, which determines the relevance of the study of changes in the functioning of the cardiovascular system to develop measures to correct adverse conditions and improve physical and mental health. The purpose of the work was to determine the features of changes in heart rate variability of students under the influence of mental and physical activity, taking into account gender characteristics. Material and methods. The article presents the results of a study of heart rate variability of 128 students (65 male and 63 female) of the Petro Mohyla Black Sea National University aged 17-25 years. All students had indicators of variability of resting heart rate, after mental and physical activity on short recordings of the cardio signal (2 minutes), obtained with the help of rhythm "MPFI rhythmograph-1" and EasyHRV software (LLC "ASTER-IT", Kharkiv). We used the proofreading method by Kryvonosov M. V. et al. (2001), which consisted of finding and selecting a specific letter in test tables for 20-25 minutes. Aerobic exercise consisted of running a distance of 2000 m on a rowing machine Concept-2 for 10 minutes. The research results were processed using descriptive statistics and non-parametric criteria. Results and discussion. The results of research showed that at rest almost all statistical and temporal indicators of heart rate variability of boys and girls were within the age norms. Mental load did not lead to a significant deterioration of the indicators studied, which indicated the stereotype of reaction. Exercises led to a significant deterioration in the cardiovascular system of students, as evidenced by a significant decrease relative to the lower limit of the norm of SDNN and RMSSD (almost four times); increase in the index of autonomic balance (above the upper limit of the norm by 90% for boys and 71% for girls); exceeding the upper limit of the norm twice with the indicators of vegetative rhythm and regulatory processes adequacy; an increase in the stress index of boys by 7 times and more than 5 times for girls, which led to exceeding the upper limit of the norm by more than 4-5 times; reduction of the total power of the cardio signal spectrum in boys by 9 times, and by 8 times in girls; power of the spectrum of very low frequencies twice, low frequencies by 5-8 times, high frequencies by 6-11 times. Conclusion. Low energy spectral parameters, as well as reducing the variability of cardio intervals and increasing the stress index are manifestations of hyperadaptive response to exercise and indicate low adaptive capacity of students, which requires the introduction of rehabilitation activities