“Only when our clever brain and our human heart work together in harmony can we achieve our true potential.”
In Heart Rate Variability: Finding the Pulse on Your Recovery, I discussed some of the physiological processes that contribute to making your heart rate variable. Stated briefly, “heart rate variability is the average measurement of the differences in time between each heart beat.”1 Your heart rate is not static—it naturally speeds up and slows down. Generally speaking, the more variable your heart rate, the better the condition of your autonomic nervous system. This is important to understand as it helps you make better decisions regarding your workout retinue and intensity from day to day, in terms of your recovery.
However, there is far more you can glean from heart rate variability in terms of psychological processes and your behavior. Your mood can affect your physiology, and as discussed in Yoga and Physiology, you can utilize physiological systems to affect your mood, and thus improve your behavior. In Yoga and Physiology, I discussed this in general terms regarding parasympathetic nervous system activation, with an emphasis on the vagus nerve. In this article, I will build on the information given in Yoga and Physiology, as well as expand upon the psychophysiological ramifications of heart rate variability that were only touched upon in the last article.
Let’s start with …
A Model of Neurovisceral Integration
Knowing what systems are in place that modify heart rate in an ongoing basis makes it possible to determine, to some extent, how well particular systems in your body function. I have only touched on respiratory sinus arrhythmia, and autonomic control of the heart. What you want to consider is that your autonomic nervous system connects to other systems as well, modifying those systems or receiving inputs from those systems to modify others. Including the heart.1
Systems governing cardiac autonomic activity, and thus heart rate variability, are linked to and effect other regulatory systems which—according to the neurovisceral integration model—can be described as a functional and structural network:
Functionally, this network includes attentional regulation, classical conditioning, affective information processing, and behavioral and physiological flexibility. Structurally, the network includes central nervous system structures, particularly the cingulate cortex, and peripheral endorgans, particularly the cardiovascular system.2
So, what are some of these other systems that connect to, influence, and are influenced by the autonomic nervous system? There are a number of systems at work, including, but not limited to, the Central Autonomic Network, the Rostral Limbic System, and the “emotion circuit,” three systems with a large overlap of their included parts:
Structurally, the [Central Autonomic Network] includes the anterior cingulate, insular, and ventromedial prefrontal cortices, the central nucleus of the amygdala, the paraventricular and related nuclei of the hypothalamus, the periaquaductal gray matter, the parabrachial nucleus, the nucleus of the tractus solitarius, the nucleus ambiguus, the ventrolateral medulla, the ventromedial medulla, and the medullary tegmental field. The primary output of the [Central Autonomic Network] is mediated through the preganglionic sympathetic and parasympathetic neurons. Importantly, these neurons innervate the heart via the stellate ganglia and vagus nerve.2
The medulla oblongata is essentially a point of origination for the vagus nerve, as briefly discussed in Yoga and Physiology. Other structures associated with the parasympathetic nervous system include the Nucleus of the Tractus Solitarius, the nucleus ambiguus, and the amygdala. Here, we see these engaged with other structures in the Central Autonomic Network. Furthermore, several of these structures are found in the Rostral Limbic System and “emotion circuit.” The Neurovisceral Integration Model posits that these systems “are one and the same functional network identified by different researchers from differing orientations … and serves to modulate psychophysiological resources in attention and emotion.”2
This is a general overview of many of the structures that serve to “modulate psychophysiological resources in attention and emotion.”2 Psycho=thought and behavior, physiology=body and movement. While the details are a bit much to thoroughly comprehend what’s happening in each structure and what role they play, it is important to understand that these structures and systems all interact with each other. Understanding this, you can begin to see how these structures and systems influence your heart rate, and, in turn, how you can utilize physiological systems to influence how you behave and act. But before we get into how heart rate variability is linked with your mood, let’s look at why this is important.
A popular meme in the yoga community is this idea that you “bend so you do not break.” The illustration can come from different flora in nature, but my favorite is that of the willow: “The willow submits to the wind and prospers until one day it is many willows — a wall against the wind.”7 It’s a powerful idea, and one entirely relevant to how you ought to operate in life: to be flexible, to be able to “go with the flow,” to move with changes that occur at any level without being debilitated by them in any way, or for very long.
The systems discussed in the prior section all contribute to a concept referred to as psychological flexibility — a mental and behavioral “bending,” also known as self-regulation — which can include all of the following:
Psychological flexibility spans a wide range of human abilities to: recognize and adapt to various situational demands; shift mindsets or behavioral repertoires when these strategies compromise personal or social functioning; maintain balance among important life domains; and be aware, open, and committed to behaviors that are congruent with deeply held values.6
To be psychologically flexible is to have at your disposal these tools necessary to address challenges that arise in a functional and responsible manner. These tools also include the abilities to adapt to fluctuating situational demands, reconfigure mental resources, shift your perspective, and balance competing desires and needs.6 Without the ability to successfully do any of these things, situations that are not challenging can become challenging, and challenging situations can quickly get out of control. Your ability to successfully navigate the waters of life are dependent on the proper operation of the physiological systems that govern your mental processes and behaviors through which these tools function.
In fact, “an absence of flexibility is linked to certain variants of psychopathology. These pathological processes span cognitive rigidities such as rumination and worry, patterns of behavioral perseveration, as well as a relative inability to rebound following stressful events, and difficulties planning and working for distant goals.”6 Furthermore, Generalized Anxiety Disorder can be added to the list, as it “is characterized by excessive, unrealistic apprehension. This persistent state is supported by attentional mechanisms such as hypervigilance, scanning, and a pre-attentive bias for threat information.”2
“Cognitive rigidities” is an apt moniker to describe these particular disorders of affect. Lacking psychological flexibility, mental processes and behaviors become rigid; you almost become stuck in a particular state:
… disorders of affect, including anxiety disorders, may be viewed as a kind of distorted emotional state space in which an individual is unable to shift into an attractor or emotion that is appropriate for a given set of environmental demands. As such the individual is ‘stuck’ in an attractor or behavioral pattern that is not responsive to the demands placed upon it by the environment. This is manifested in inflexibility at various levels of system organization. Put another way, the individual is unable to select the appropriate response or, more often the case, unable to inhibit the inappropriate response. Thus, the response selection mechanism is somehow corrupted.”2
When all of your system processes function appropriately, the tools available to you are numerous when addressing challenges that arise. Psychological flexibility is, essentially, a naturally occurring state. However, when some of these processes malfunction or are disorganized, cognitive rigidity sets in, making challenges and situational demands difficult to deal with and can become health problems on a much larger scale:
This ‘reading’ of the emotional environment requires the selection of certain information and the disregarding of other information from a complex input that includes internal as well as external cues. When this ability to effectively process affective information is compromised for whatever reason, the individual is unable to maneuver efficiently in its environment. Inefficiency in affective information processing leads to affective dysregulation. When this inefficiency becomes severe, various forms of pathology are said to exist such as alexithmia, depression, panic disorder, generalized anxiety disorder, hostile personality, hypertension, and coronary heart disease to name a few.”2
I highlighted hypertension and coronary heart disease to illustrate the point that the malfunctioning of these behavioral processes are not limited to negatively affecting psychological states, but that they extend into the physiological realm. How can cognitive rigidity lead to coronary heart disease?
The relationship between psychological stress and cardiovascular reactivity has long been suggested as an explanation for the association between psychological stress and [cardiovascular disease]. It is known that chronic psychological stressors can lead to increased risk of arteriosclerosis, hypertension, and other metabolic disorders, while acute stressors result in acute increases in blood pressure, [heart rate], and decreased metabolic efficiency.8
This brings us back to the Model of Neurovisceral Integration and the inherent stipulations that psychological and cardiovascular processes are interconnected. This, then, is the crux of the model:
… the neurovisceral integration model, which suggests that neural networks implicated in autonomic, emotional, and cognitive self-regulation are also involved in the control of cardiac autonomic activity.3
Now that we’ve come back to the heart, it is time to discuss the link between emotional and behavioral processing and heart rate variability.
Heart Rate Variability and Emotion Regulation
So how does heart rate variability factor into our understanding of emotional and behavioral regulation?
[Heart rate variability] not only reflects physiological regulation, but also cognitive and emotional regulation. Several studies have demonstrated that individuals with greater levels of resting [heart rate variability] have greater emotion regulation and responding, as well as executive functioning. Further, greater capacity to respond to environmental challenges (i.e., greater [respiratory sinus arrhythmia] reactivity) is associated with attentional and emotional processes that facilitate adaptive responses to stress. In contrast, individuals with lower levels of resting [heart rate variability] have been found to have poorer emotion regulation abilities and deficits in attentional control and working memory.4
Basically, the more your heart rate varies at rest, the better your capability at regulating your emotions and behavior in terms of responding to environmental challenges, i.e. psychological flexibility. The less your heart rate varies at rest, the poorer your ability to respond appropriately to environmental challenges, i.e. cognitive rigidity. Furthermore, lower resting heart rate variability suggests shorter and ill-controlled attention spans and poorer memory. This can work two ways: your higher-level mental processing centers (prefrontal cortices, etc.) may be operating poorly, and as a result are affecting your heart rate variability. Likewise, your heart may be in poor working order and may be affecting higher-level mental processing centers. In either case, a positive feedback loop is created in which the heart and the mind continuously debilitate each other. “Evidently there is a link between [heart rate variability] and the prefrontal-subcortical circuits critical for cognitive and emotional self-regulation.”3
So, the psychological processes that influence your emotions and behavior are linked with the physiological processes that influence heart rate variability. As stated, heart rate variability reflects cognitive and emotional regulation, inherently suggesting that the systems involving each are interrelated. In discussing the Neurovisceral Integration Model, the Central Autonomic Network was broken down into it’s respective parts. One important detail here is that “the components of the [Central Autonomic Network] are reciprocally interconnected.”2 ‘Reciprocal’ being the key term. These structures are not connected as a one way system; “this allows for continuous positive and negative feedback interactions and integration of autonomic responses.”2
All of this exposition for this main point: if prefrontal and subcortical structures can influence heart rate variability, and these structures are reciprocally interconnected, it follows that by improving your heart rate variability, you should be able to improve the function of these higher-level structures. And, in fact, this is what researchers are finding:
… recent findings suggest that [heart rate variability] itself influences brain and emotional function. In these studies, participants are taught to increase their [heart rate variability] by breathing at around 10s per breath. This .1 Hz frequency is a ‘resonance’ frequency at which paced breathing induces oscillations in heart rate at an especially high amplitude … A recent meta-analysis of 24 studies revealed that [heart rate variability] biofeedback reduced self-reported stress and anxiety with a large effect size … [heart rate variability] biofeedback also has other positive effects on emotions. Coronary artery disease patients randomly assigned to [heart rate variability] biofeedback during resonance breathing instead of a wait-list control showed decreased expressive and suppressive hostility and these effects were maintained a month after the 6-week intervention ended. Likewise, veterans with post-traumatic stress disorder randomly assigned to [heart rate variability] biofeedback during resonance breathing showed improved symptoms after 8 weeks of [heart rate variability] biofeedback whereas those assigned to treatments as usual did not show significant reductions in symptoms. In addition, patients with post-stroke depression randomly assigned to treatment-as-usual in addition to [heart rate variability] biofeedback during resonance breathing showed greater reduction in some indices associated with depression than those not assigned to [heart rate variability] biofeedback.9
Resonance breathing? How does this even begin to work? In Yoga and Physiology I briefly begin to describe the process by saying, “… we voluntarily stimulate our vagus with our breath … As we do breath work … we stimulate our vagus and thus begin to produce the physiological changes that occur in activating the [parasympathetic nervous system].” In understanding the process of respiratory sinus arrhythmia, you can see how managing your breath and taking the time to elongate each exhale would bring a greater rest response to your heart. Furthermore, the team over at the HeartMath Institute have been studying the Heart-Brain connection for some time and propose:
… the heart, as the most powerful generator of rhythmic information patterns in the body, acts effectively as the global conductor in the body’s symphony to bind and synchronize the entire system. The consistent and pervasive influence of the heart’s rhythmic patterns on the brain and body not only affects our physical health, but also significantly influences perceptual processing, emotional experience, and intentional behavior.10
So now, we’re really back at the heart, and getting into the heart of the matter (see what I did there?).
Improving Your Heart Rate Variability
So, you’re now aware that heart rate variability offers a way to measure the health and efficiency of your Central Autonomic Network and Autonomic Nervous System, as well as give insight to additional processes relevant to psychological flexibility. And you are also now aware that you can improve your heart rate variability, and by doing so can bring some of these other systems into better performance. One way that was briefly mentioned in the last section was described as ‘resonant breathing’ and detailed as taking a breath cycle of 10s over the course of several minutes. This works best when done over a 10-minute span daily, over the course of several weeks. You can certainly afford to sit for 10 minutes and just breathe every day, right?
Yeah, right. We are all aware of the value of meditation, and yet how many of us actually sit our asses down and meditate daily? So, you don’t meditate regularly, and you sure as hell don’t want to sit and stare at a timer and just breathe for ten minutes. So, what then?
By now, you should know what I’m going to say. I’m a yoga instructor, personal trainer, and group exercise instructor. What do you think the answer is, when asked how to improve your heart rate variability?
1Castaneda, J. A. (2018). Heart Rate Variability: Finding the Pulse On Your Recovery. Retrieved August 30, 2018, from https://strvtmvmnt.co/hrv
2Thayer, J. F., & Lane, R. D. (2000, December). A model of neurovisceral integration in emotion regulation and dysregulation. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/11163422
3Park, G., & Thayer, J. F. (2014). From the heart to the mind: cardiac vagal tone modulates top-down and bottom-up visual perception and attention to emotional stimuli. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4013470/
4Hamilton, J. L., & Alloy, L. B. (2016, December). Atypical Reactivity of Heart Rate Variability to Stress and Depression: Systematic Review of the Literature and Directions for Future Research. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5233715/
5Thayer, J. F., & Lane, R. D. (2009, February). Claude Bernard and the heart-brain connection: Further elaboration of a model of neurovisceral integration. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/18771686
6Kashdan, T. (2010, March 12). Psychological flexibility as a fundamental aspect of health. Retrieved from https://www.sciencedirect.com/science/article/pii/S0272735810000413?via=ihub
7Herbert, F. (2015). Dune. London: Hodder.
8Huang, C. J., Webb, H. E., Zourdos, M. C., & Acevedo, E. O. (2013, November 07). Cardiovascular reactivity, stress, and physical activity. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24223557
9Mather, M., & Thayer, J. (2018, February). How heart rate variability affects emotion regulation brain networks. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/29333483
10McCraty, R., Atkinson, M., Tomasino, D., & Bradley, R. T. (2009, December). The Coherent Heart: Heart–Brain Interactions, Psychophysiological Coherence, and the Emergence of System-Wide Order. Retrieved from https://www.heartmath.org/research/research-library/basic/coherent-heart-heart-brain-interactions-psychophysiological-coherence-emergence-system-wide-order/
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