The influence of anxiety and academic stress on physiological tremor indicators of the hand in female individuals

Stress is the cause of increased physiological tremor [4]. Educational activity in itself is intense and stressful [6], especially during the period of writing modular test papers or passing exams. Anxiety can increase tremor due to increased excitability of the nervous system, which is manifested by increased reactivity of motor neurons. This increases the tendency to uncontrolled muscle contractions and, accordingly, tremors. The purpose of the work was to investigate the effect of educational stress (modular control work) on indicators of physiological tremor of the upper limbs of female students in general and depending on their level of anxiety in particular, as well as to find out the existence of a relationship between indicators of tremor and heart rate and blood pressure of the subjects. We analyzed the amplitude-frequency indicators of the tremor of the right and left hand, as well as the level of anxiety of 14 female students aged 19–20 years. Subjects provided written consent to participate in the study. All female students had no history of neurological and motor disorders, 93 % (13/14) of them were right-handed. Tremor frequency and amplitude were recorded in two positions - in a free position (the hand hung from the support surface with the palm down) and in a postural position (the hand was placed parallel to the support surface with the palm down) using an MPU6050 accelerometer (InvenSense, China). The author’s program was used to read the results from the accelerometer. Blood pressure was determined by the Korotkov method. Blood pressure and heart rate were measured using an oscillometric tonometer Microlife BP N1 Basic (Switzerland). To determine the level of anxiety, the DASS-21 questionnaire was used, on the basis of which the subjects were divided into three groups according to the level of anxiety: moderate (1–5 points), medium (6–7 points) and strong (8–20 points). The first group included 5 female students (one of them left-handed, the rest right-handed), the second group included 4 female students (all right-handed), and the third group included 5 female students (all right-handed). The probability of the difference between the arithmetic means of two samples was estimated by the Student’s test under the condition that the data were normally distributed. If the distribution deviated from normal, the Mann-Whitney test was used to compare the samples. For the entire group of female students (n=14), indicators of physiological tremor of the right and left limbs both in the free and in the postural position of the hand did not differ before the modular control and on a regular school day. After dividing female students according to the level of anxiety, it was found that in the group with a moderate level of anxiety there was a decrease in the frequency of tremor of the right hand in the free position of the hand by 10.2 % (p≤0.05) before the module control compared to the school day without measuring knowledge. On days without modular control of knowledge in persons with a strong level of anxiety, a direct correlation was established between the level of anxiety and the frequency of physiological tremor of the left hand (r=0.99; p≤0.05), as well as between the level of anxiety and the amplitude of tremor of the right hand hands (r=0.95; p≤0.05) in a free position. The frequency of left hand tremor in this group was lower by 12.87 % (p≤0.05) compared to individuals with an average level of anxiety. In persons with a moderate level of anxiety, a strong correlation was observed between the level of anxiety and the frequency of tremor of the left (r=0.84; p≤0.05) and right (r=0.76; p≤0.05) hands in a free position in the absence of modular control of knowledge. In the entire sample of female students under conditions of academic stress, a strong correlation was established between heart rate and tremor frequency (r=-0.70; n=14; р≤0.05), as well as tremor amplitude (r=0.75; n =14; p≤0.05) of the right hand in the postural position of the hand. Immediately before writing the modular control paper, there was a negative correlation of average strength between the amplitude of tremor of the right hand in the free position of the hand and Amax (r=-0.62; p≤0.05) and Amin (r=-0.63; p≤0, 05). So, the amplitude and frequency of the physiological tremor of the right and left hand of female students in a free position of the hand partially depends on the level of anxiety of the person. In the absence of a control task, individuals with a high level of anxiety had a statistically significantly lower frequency of left hand tremor compared to individuals with an average level of anxiety. In persons with a moderate level of anxiety, a decrease in the frequency of tremor of the right hand in the free position of the hand was observed before the modular control compared to the educational day without measuring knowledge. In the entire sample of female students, under conditions of educational stress, a correlation was established between heart rate and the amplitude and frequency of tremor of the right hand in the postural state of the hand, as well as between ATmax and ATmin and the amplitude of tremor of the right hand in the resting state of the hand.