During my sports medicine fellowship in the Fall 2007 I was introduced to a heart-mind-body connection that has fascinated me since. The beat-to-beat change in rate of cardiac rhythm known as heart rate variability (HRV) is a measure of the automated response to stress. In no other way has the heart & brain connection, the mind-body, been more evident to me in science.
The autonomic nervous system (ANS) as Carl Sagan described in his book, Cosmos (1980), is the lizard brain. Joe Rogan & others have described this as the monkey mind. In summary this is to say, we are constantly responding to stressors from our environment including physical & emotional signals. Our conscious cognitive awareness is usually unimpressed by the automatic responses. Our ego often takes credit for our thoughts & actions, but the reality is that many ideas & subsequent activities are programmed through the automatic responses inherited in DNA & learned in life experience. Awareness of the monkey mind can allow us to modify our relationship to stress.
THE BASIC SCIENCE of HRV: The heart is controlled by a pacemaker, the sinoatrial node. This bundle of tissue at the top of the heart determines a set-point for the rate at which the pump ejects blood through your body. It is influenced by various factors that either speed it up, or conversely, slow it down. Simply, the fight & flight mechanism – the sympathetic nervous system – senses danger and increases blood flow to muscles, dilates pupils, expands airways, & readies the animal to run or fight. It is fueled by adrenaline & bundles of nerves called ganglia. The opposing force is the rest, digest, & think system – the parasympathetic nervous system. This system is predominantly mitigated by the vagus nerve & acetylcholine. HRV is influenced by the balance of these two opposing forces.
QUICK HISTORY: Scientific studies performed as far back as the 1970s correlate health & wellbeing to HRV. In fact, with further investigation my fascination with this biomarker grew when I found studies performed in the 1990s showing that people with lower HRV after heart attack had a higher rate of death in hospitals. These studies were not new at the time of my discovery, so how had it been that this measurement was not more well known? How did I go through medical school & residency without ever having heard of this parameter of health? The quick answer is that in uncontrolled settings the signal to noise ratio was not favorable due to the fact that many parameters can influence the data. Also, technology had yet to make measurement widely available and easy enough to obtain.
WHY IT MATTERS: New developments have allowed for easier access to collecting this biomarker. Science has elucidated methods by which measurements can be controlled and useful. By monitoring one’s physical response to specific variables such as sleep, hydration, exercise, & emotional stress, controllable factors can be modified and health improved. Previously unconscious stressors & physiological responses can be brought into the light. Lifestyle changes can have major impacts on health that are measurable beyond our current understanding of more basic vital signs. Exercise is medicine. Food is medicine. Stress is a major determinant of health. The HRV biomarker can help to measure the response individuals have to the above factors and more, as well as possibly predict when the system needs rest/recovery before injury & disease occur.
ENHANCING HRV: Beyond improvements seen with proper exercise, sleep, nutrition, stress management, there are other ways of improving HRV. The most interesting influential factor impacting HRV is the increase & decrease in heart rate associated with your breath. As air enters your body the heart’s pace speeds up. With exhalation the heart slows down. Meditative work can strongly influence HRV during practice & may have lasting impact with sustained engagement in paced breathing. Biofeedback is a process of continuously monitoring HRV while pacing breath to amplify the physiological response. This concept resonates with me for may reasons. Most of all because meditation is tied to many religions, cultures, & even agnostic circles understanding its health benefits. But even more so for me personally, because my scientific mind loves that there is a measurable physiological response confirming ancient wisdom in these traditions.
Over the years I have used various products to measure and enhance my own HRV, each with their own merits. I have measured the HRV of my patients. I am engaged in scientific research on this front as well. I routinely teach & monitor my patient’s response to biofeedback. This year I will work with HRV4Training & Marco Altini to track HRV in myself & some of my colleagues at work, describing the experience and insights gained. Stay tuned for more. This should be a fun learning experience for us, and hopefully you as well.