# Psychophysical State Aspect during UAV Operations
## 3 Results  
The research focused on cardiovascular system work--more specifically, on heart rate variability (HRV). The values of this factor can be an adequate physiological correlate of cognitive functioning. The HRV parameter is considered an indicator of autonomic control [20]. The most commonly used methods of quantitative and qualitative analysis of heart rate variability can be divided into several groups: time-domain methods, frequency-domain methods, time-frequency-domain methods and nonlinear methods. Based on the measurements performed, time-domain and nonlinear analysis were chosen to perform calculations. The measurement data used to determine the parameters that describe the HRV were analysed using dedicated software (Kubios HRV Standard 3.5.0 software). The first stage of the analysis was to remove artifacts from the measurements. After their removal, the record from the measurement did not present the direct length of RR intervals, but rather NN intervals, which are the values of RR intervals obtained after removing noise. Based on prepared samples, the parameters of the HRV were determined. HRV is expressed by differences in the intervals between the peaks of R waves (Figure 2), consecutive QRS complexes of sinus origin which describe the stimulation of the muscles and of the heart ventricles. The samples used in the analysis were 5 min long, which is in line with the principles of conducting short-term variability (STV) analysis. The material was selected, and then, using the STATISTICA software (STATISTICA 13.3 software), the parameters for the time-domain and nonlinear analysis were determined. For a given subject, the parameters were obtained for the reference measurement (at rest) and the comparative measurement (during training). Figure 1: Results obtained on the basis of the personal questionnaire for student operators. The figure shows: (**a**) the rating of reaction speed; (**b**) the rating of cognitive abilities; (**c**) the age of the respondents; and (**d**) motivation to obtain a certificate of qualifications (own elaboration). The following variables were selected as part of the analysis:  
* \(\overline{\pi}\) RR--average length of RR interval (ms),
* \(\overline{\pi}\) HR--average heart rate (bpm),
* HR max.--maximum value of heart rate (bpm),
* HR min.--minimum value of heart rate (bpm),
* SDNN--standard deviation of NN interval (ms),
* RMSSD--root mean square of successive differences between each RR interval,
* HRV--histogram density function for the N interval divided by its height. The parameter is usually used for 24 h measurements,
* SD1 parameter--determined on the basis of the Poincare diagram. This SD parameter is perpendicular to the line of identity. This indicator is characterised by a temporary variability (ms) value. An example of a Poincare diagram for one of the subjects is shown in Figure 3,
* SD2 parameter--determined on the basis of the Poincare diagram. This SD parameter is along the line of identity. This indicator characterises long-term heart rate variability and provides information about general variability,
* SD1/SD2--relationship between SD1 and SD2. After analysis in KUBIOS, each respondent was described by 10 variables in 2 types of measurements (a total of 20 variables per participant). Using the determined variables, statistical analysis was performed. This way, it was possible to perform tests for normality of distribution in individual variables, as well as significance tests. To check the normality of the distributions, the Shapiro-Wilk test was used. The results of the test were analysed with a significance level of 0.05 (Table 1). As can be seen in Table 1, three variables were not normally distributed. Testing was necessary to properly select the type of significance tests. For variables with a normal distribution, a Student's \(t\)-test of significance was used, and for variables that were not characterised by a normal distribution, the Wilcoxon test was used [32]. Table 1 shows the significance test results for each tested variable.