Physiological coherence in healthy volunteers during laboratory-induced stress and controlled breathing.

Physiological coherence has been related with a general sense of well-being and improvements in health and physical, social, and cognitive performance. The aim of this study was to evaluate the relationship between acute stress, controlled breathing, and physiological coherence, and the degree of body systems synchronization during a coherence-generation exercise. Thirty-four university employees were evaluated during a 20-min test consisting of four stages of 5-min duration each, during which basal measurements were obtained (Stage 1), acute stress was induced using validated mental stressors (Stroop test and mental arithmetic task, during Stage 2 and 3, respectively), and coherence states were generated using a controlled breathing technique (Stage 4). Physiological coherence and cardiorespiratory synchronization were assessed during each stage from heart rate variability, pulse transit time, and respiration. Coherence measurements derived from the three analyzed variables increased during controlled respiration. Moreover, signals synchronized during the controlled breathing stage, implying a cardiorespiratory synchronization was achieved by most participants. Hence, physiological coherence and cardiopulmonary synchronization, which could lead to improvements in health and better life quality, can be achieved using slow, controlled breathing exercises. Meanwhile, coherence measured during basal state and stressful situations did not show relevant differences using heart rate variability and pulse transit time. More studies are needed to evaluate the ability of coherence ratio to reflect acute stress.