*5.1. Psychophysiological Coherence*

Psychophysiological studies indicate that bidirectional heart–brain communication has been recognized for over a century [27]. The heart possesses an intrinsic nervous system, capable of autonomous, functional decisions [9]. The heart communicates more with the brain than with any other organ [9]. Intricate heart rate variability patterns provide vital communicative links within the body, as well as between and among people, the ecology, and the cosmos. The sympathetic and parasympathetic (vagal) branches of the autonomic nervous system (ANS) function similarly to an accelerator and a brake, reflecting dynamic, resonant HRV patterns, signaling adaptation, resilience, and general health for diverse forms of healthcare assessment and intervention. HRV oscillations are typically categorized into very low frequency (VLF) bands between 0.0033 and 0.04 Hz, low frequency (LF) bands between 0.04 and 0.15 Hz, and high frequency (HF) bands from 0.15 to 0.4 Hz [28]. The psychophysiological coherence experience of zoned performance is closely related to Antonovsky's [29] sense of coherence construct of the world as meaningful, manageable, and comprehensible, which also provides healthcare initiatives with a valid, unifying, theoretical, and practical rationale [30].
