“…Complex underlying regulation mechanisms and personal peculiarities are still not fully disclosed by traditional HRV measures, and other than traditional HRV measures are not always more helpful in clinical context though research on new ways to evaluate HR dynamics is still encouraged (Sassi et al, 2015)). Alternative approach would be to use statistical techniques to invert mathematically formulated forward models (Bach et al, 2018), or fitting HR dynamics to a comprehensive Regulation at lower levels are more deterministic, more investigated and numerous heart-regulation models, tried to include this knowledge, for example models of Ursino (1998) and it's extensions (Ursino and Magosso, 2000;Hsing-Hua Fan and Khoo, 2002;Magosso et al, 2002;Cheng et al, 2010;Albanese et al, 2016;Park et al, 2020), Kotani et al (2005) and it's derivations (e.g. Ishbulatov et al, 2020), and other closed loop models (Van Roon et al, 2004;Ortiz-León et al, 2014) and specific purpose open loop models (Randall et al, 2019) for humans.…”