## 4 Discussion
This change in position could explain such a rise in RMSSD in the first 3 min segment--blood pressure is always higher in the standing position, and it would not require such a level of parasympathetic activation if participants were left in the standing position to recover [9]. Furthermore, the results of the study by [PERSON] et al. support our findings by demonstrating that the recovery rate after submaximal HR exercise is higher in the supine position compared to the sitting position for participants [43]. Afterwards, a more gradual time-dependent recovery of parameters was observed, probably due to the compensation of metabolic changes after the physical activity. This is in accordance with the observed weak negative correlation between BF and RCA. In relation to the relaxed state, HR was significantly higher in recovery in all five 3 min segments (Table 3). BF did not differ from the values in the relaxed state, except in the third and fourth 3 min segments, where we observed a significant increase in BF in relation to the relaxed state (Table 5). This happened in parallel with the lowest level of parasympathetic activity in recovery, although we failed to find any correlation between BF and RMSSD in the recovery period (Table 4). RCA did not differ significantly in the recovery period in comparison to the relaxed state in any time segment (Table 6). In conclusion, the timeframe for recovery in our study was probably not long enough in order to obtain all of the examined parameters at the pre-exercise state levels. In general, the duration of recovery is primarily dependent on the intensity of the physical activity, as well as on its modality and duration [35]. In addition, the recovery duration may also be influenced by the age of the participants and their exercise capacity level. It has been found that athletes require less time to recover compared to non-athletes [43]. Moreover, it has been proven that prepubertal children, as well as trained adults, recover faster and have a quicker parasympathetic reactivation after a maximal HR running test compared to untrained adults [44]. Furthermore, different environmental conditions can impact the speed of recovery after exercise. The results of [PERSON] et al. [15] showed that hypoxia significantly delays parasympathetic reactivation after submaximal HR intensity exercise. This makes a comparison of the results of studies rather difficult, because each includes a different protocol, duration, and intensity of physical activity. By analyzing the entropy values, we observed a significantly higher SampEnRR value in the recovery period in comparison to exercise, but still significantly lower than in the relaxed state (Figure 6). This was expected, as in the recovery period, the parasympathetic response is activated and the sympathetic response withdraws slowly, resulting in a more complex cardiac signal. However, we did not obtain any statistical difference in the SampEnResp values between any state, even though there were marked changes in BF and RCA (Figure 6). Asynchrony between the signals in recovery was not significantly different in comparison to exercise, nor in comparison to the relaxed state (Figure 6). This could be the result of a specific pattern of changes in the autonomic nervous system in the recovery period, in which signals slowly regain the characteristics of those in the relaxed state in terms of asynchrony and complexity. Lastly, we ran a multiple regression analysis model to determine the relationship between the average 3 min HR, RMSSD, and BF segments in recovery and the other examined parameters (Tables 8-10). We found that the average HR rate in the first and second 3 min HR segments in recovery was strongly predicted by the average HR value achieved in the third 3 min segment of exercise. It is possible that the behavior of parasympathetic activity influenced the observed results. Namely, RMSSD was already minimal in the third 3 min segment in exercise and remained minimal until the end of exercise.