**5. HeartMath Coherence Model**

Theoretically, the HeartMath coherence model includes all the usual meanings of the term coherence, as implied in such terms as relationship, harmony, order, stability, consistency, synchrony, logic, and by the idea of the whole being more than the sum of its parts [8]. In academia, coherence refers to the internal integrity of an argument or thesis. Linguistically, it refers to intelligibility. Physiologically, the concept of coherence includes the synchrony of the circulatory and respiratory rhythms associated with overlapping sine wave patterns. In physics, it implies phase relationships. Auto-coherence, or auto-correlation, indicates stability in a single wave form; cross-coherence, among multiple waveforms, while phase locking and resonance include the concept of harmony in various rhythmic activities. In math and statistics, the term coherence implies correlation. In dynamic systems theory, it means connectedness, alignment, resonance, and optimal energy utilization.

From a psychophysiological perspective, coherence interconnects positive emotions with the cardiovascular, respiratory, immune, and nervous systems [9]. From a human as well as a social perspective, coherence applies to couples, teams, groups, organizations, and communities. Coherent relationships promote communication, synchronized behavior in rowing teams, and groups with similar goals. From a global perspective, communities and countries working cooperatively can cause ecological and planetary peace and harmony. Experientially, HeartMath praxis is accompanied by the sentient, increasing awareness of the synchronization of pulsation, respiration, and the renewing of positive feelings, whereby emotions such as peace and love are cumulatively experienced as radiating throughout the body, and among people and the wider world in harmonious interconnectedness.

Various HRV-related psychophysiological theories resonate with the HeartMath coherence model. Resonance theory is founded on heart rate variability biofeedback (HRVB) studies, which indicate that optimal heart rate oscillations occur via paced respiration at a frequency of about 0.1 Hz. Polyvagal theory, which hypothesizes social evolutionary mechanisms, advocates RSA and enhanced HRV for improved health and well-being. The neurovisceral integration model postulates a central autonomic network (CAN) related to social, cognitive, affective, and physiological regulation [9].
