“…One widely used measure of autonomic nervous system (ANS) activity is the beat-to-beat variations in cardiac rhythm as indexed by heart rate variability, which is currently one of the most widespread methods for the quick assessment of the functional state of different autonomic regulation elements and hence the whole body (Fagundes et al, 2011, Jarczok et al, 2013, Voltas et al, 2016. HRV has been independently associated with morbidity and mortality, especially in relation to cardiovascular disease (Jarczok et al, 2013, fatigue (Fagundes et al, 2011), work stress (Loerbroks et al, 2010), and psychological status (Fagan et al, 2017, Dzhebrailova & Suleymanova, 2012, Koenig et al, 2018. Psychological stress is thought to be a dominant factor in the lives of many people.…”