and rate varies without our conscious awareness due to changes in the inputs tothe respiratory centers in the brain stem that control respiration.Among these inputs is the afferent neurological information from the heart and cardiovascularsystem. Our breathing rate is affected by and often synchronized to the cardiac cycle, whichmeans that changes in our heart rate and rhythm can affect our breathing rate and patterns.12During sleep or rest, coupling between the cardiac cycle and respiration is the strongest, and attimes of stress, coupling between the heart and respiration becomes disrupted (Langhorst,Schulz, & Lambertz, 1986; Raschke, 1986a, 1986b; Turpin, 1986).It is well established that changes in emotional states also alter breathing rates. Agitated statessuch as anger and frustration increase the breathing rate and reduce tidal volume (the depth of thebreath), while positive emotional states slow the breathing rate and increase tidal volume. Theseemotion-related changes in breathing are likely to result, at least in part, from changes in inputfrom the cardiovascular centers.Because respiration modulates the heart rhythm, it can be intentionally used as a powerfulintervention that can have quick and profound body-wide effects. As we have conscious controlover our breathing rate and depth, we can consciously modulate the heart rhythm and thuschange the afferent neural patterns sent to the brain centers that regulate autonomic outflow,emotion, and cognitive processes. Our experience with breathing exercises is that they areeffective primarily due to the fact that they modulate the hearts rhythmic patterns.However, it is important to emphasize that coherence is associated with positive emotionsindependent of conscious alterations in ones breathing rhythm. In our earlier studies, whichwere focused on the physiological correlates of different emotional states, instructions to subjectspurposely made no mention of altering breathing rates or depths. We found that when sustainedpositive emotional states were maintained, increased heart rhythm coherence and entrainmentThe effects of lung inflation are mediated by sensory neurons in the lungs that respond to stretch. Theseneurons increase their firing rate as the lungs expand upon inspiration. The output from these neuronstravels to the brain stem and inhibits the parasympathetic outflow from the brain to the heart, resulting inan increase in heart rate. During expiration, the stretch is reduced and the inhibition is removed. The heartrate is quickly reduced. This interaction between the lungs and brain stem is only one source of RSA;however, it provides an easy way to conceptualize RSA.12The influence of afferent information from the heart on respiration was studied in great detail in the1940s and 1950s. The cardiovascular afferent systems excite the respiratory centers, and if this input isinhibited, so is respiration. For a review of this earlier research, see Chernigovskiy (1967).INTEGRAL REVIEWDecember 2009Vol. 5, No. 2between the heart rhythm, blood pressure rhythms, and respiratory rhythms emerged independentof any conscious alterations in breathing pattern (McCraty et al., 1995; Tiller et al., 1996).Although breathing techniques may sometimes facilitate a feeling shift, coherence that isdriven through the use of such techniques alone does not necessarily shift ones emotional state.For example, it is possible to breathe at a rate of six breaths per minute (a 10-second rhythm) andstill be feeling anxiety or other feelings of unease.