In 335 B.C. in an area of Asia Minor known today as Turkey was born a boy named Herophilos. His intellectual gifts were cause for an earlier than normal expected move to Alexandria to begin his studies. He went on to make great contributions to medicine and came to believe steadfastly in the scientific method.
Among his discoveries were that veins carried blood and veins were different from arteries and arteries pulsed rhythmically. He was also the first known individual to measure the human heart rate using a 4,000 year old device known as a clepsydra or water clock.
Herophilos once noted, “when health is absent, wisdom cannot reveal itself, art cannot become manifest, strength cannot be exerted, wealth is useless, and reason is powerless."
It wasn’t until 2,000 years later through the use of a Physicians Pulse Watch (which included a second hand that could be started and stopped) that Reverend Stephen Hales was able to measure pulse rates accurately.
In the 1840’s Carl Ludwig invented the smoked drum kymograph. This device measured “periodic oscillations in the amplitude and timing of arterial pressure that varied during respiration.”[i] In other words, heart rate increased when breathing in and decreased when breathing out. This was the first documented evidence of respiratory sinus arrhythmia (RSA).
From this point forward beat-to-beat variation measurements made leaps and bounds with advances in technology. The electrocardiogram (EKG) was developed in 1895. According to The Cleveland Clinic[ii] an EKG is used to:
✳ assess heart rhythm ✳ diagnose poor blood flow to the heart muscle ✳ diagnose a heart attack ✳ diagnose abnormalities in the heart, such as heart chamber enlargement and abnormal electrical conduction
With the advent of the microchip computer processors, digital signal processing techniques exploded with potential in the 1960’s and 70’s. Moore’s Law, which states that computer processing speed doubles every two years, has advanced every aspect of our society to the point where today we have incredibly precise instruments as part of our mobile phones in our pockets.
One of the primary systems that can be measured accurately but only indirectly with a mobile app and sensor is the autonomic nervous system (ANS). The ANS aids in the function of the lungs, heart and blood pressure, supplies the blood vessels, stomach, intestine, liver, kidneys, bladder, genitals, lungs, pupils, heart, sweat, salivary, and digestive glands. These autonomous systems function beneath our conscious awareness, which is why they can only be measured and affected indirectly.
The ANS is divided into two components: sympathetic and parasympathetic nervous system. In many ways, but not all, these two systems act as balances for one another like the accelerator and brake in a car. Where one stimulates the body to respond, the other often inhibits that response to calm down.
One of the ways in which these two systems act as counterbalances for one another is through the fight or flight response. When a threat is perceived the sympathetic nervous system (SNS) leaps into action by shunting blood away from extremities like the hands and feet and stores the blood in the vital organs such as the heart, brain and lungs. The adrenal gland is activated which releases stress hormones such as adrenalin and cortisol into the bloodstream. This has several significant effects on the body. It causes a person’s heart rate to increase, bronchial tubes and pupils dilate, muscles to contract just to name a few.
A very serious syndrome called adrenal fatigue can happen if the body is required to transition and remain in the fight or flight state too long too often. In addition to adrenal fatigue many diseases are caused or made worse by chronic stress including heart disease, immune system suppression, anxiety, digestive issues, low energy, respiratory problems and decreased sexual function.
Conversely, the parasympathetic nervous system is called “rest and digest” to indicate its balancing effects on the body. The PNS is the system responsible for homeostasis, which is the constant monitoring of the body to keep it in a state of equilibrium. The PNS, like the SNS, is an autonomous system (running in the background outside of conscious awareness) we cannot directly influence. Yet just as the SNS can be activated by a threat, the PNS can be activated (i.e. exercised for optimal performance) by engaging in activities that calm your body and brain. This can literally be anything that is soothing to the mind like reading a book, taking a hot bath, or hiking your favorite trail in the park. There are also very direct activities that help soothe and heal the emotional body such as massages, cranial sacral work, Tai Chi, meditation or heart rate variability biofeedback (HRV).
The Marine Resiliency Study (aka SDR 09-128) is an examination by the Department of Veterans Affairs to assess the physical and emotional effects of combat on soldiers. Its broad scope covers many topics related to both the risk of soldiers getting Post-Traumatic Stress Disorder (PTSD) and post-war adaptation and the propensity for soldiers to develop PTSD.
One factor analyzed was Low Frequency (LF) heart rate variability and High Frequency (HR) heart rate variability and the relationship between the two. Low Frequency HRV has been proven to be an effective indicator of various other medical problems including sudden cardiac arrest and neuropathy (nerve damage) in diabetic patients. Dr. Arpi Minassian, lead investigator of the study explained, "Thus, when we examine the ratio between the LF and HF components of heart rate, we can derive an estimate of the balance between these two systems. A higher ratio might mean that the parasympathetic nervous system may not be working well enough to adequately 'calm' the sympathetic nervous system".
The heart rate variability of 2,160 Marines were assessed 1-2 months prior to deployment and 4-6 months after deployment using a “fingertip plethysmograph” (an optical sensor on the fingers that detects pulse).
The study concluded that those soldiers tested prior to deployment who had a higher ratio of Low Frequency heart rate variability were more likely to return with PTSD than those with an increased level of High Frequency heart rate variability. The findings support the idea that high heart variability is proving to be a powerful indicator of psychological and physical resiliency.
Heart Rate Variability Biofeedback has yet to catch the attention of pop culture the way yoga and meditation have but that will soon change. Biocom Technology, a provider of HRVB tools, writes on their website[iii], “It is believed that Heart Rate Variability (HRV) will become as common as pulse, blood pressure or temperature in patient (medical) charts in the near future. In the last ten years more than 2,000 published articles have been written about HRV. HRV has been used as a screening tool in many disease processes. Various medical disciplines are looking at HRV. In diabetes and heart disease it has been proven to be predictive of the likelihood of future events. The HRV analysis is powerful, very accurate, reliable, reproducible, yet simple to do.”
Heartmath[iv], another provider of consumer HRV biofeedback technology through a smartphone app and ear sensor, explains:
Most of us have been taught in school that the heart is constantly responding to “orders” sent by the brain in the form of neural signals. However, it is not as commonly known that the heart actually sends more signals to the brain than the brain sends to the heart! Moreover, these heart signals have a significant effect on brain function – influencing emotional processing as well as higher cognitive faculties such as attention, perception, memory, and problem-solving. In other words, not only does the heart respond to the brain, but the brain continuously responds to the heart. The effect of heart activity on brain function has been researched extensively over about the past 40 years. Earlier research mainly examined the effects of heart activity occurring on a very short time scale – over several consecutive heartbeats at maximum. Scientists at the Institute of HeartMath have extended this body of scientific research by looking at how larger-scale patterns of heart activity affect the brain’s functioning. HeartMath research has demonstrated that different patterns of heart activity (which accompany different emotional states) have distinct effects on cognitive and emotional function. During stress and negative emotions, when the heart rhythm pattern is erratic and disordered, the corresponding pattern of neural signals traveling from the heart to the brain inhibits higher cognitive functions. This limits our ability to think clearly, remember, learn, reason, and make effective decisions. (This helps explain why we may often act impulsively and unwisely when we’re under stress.) The heart’s input to the brain during stressful or negative emotions also has a profound effect on the brain’s emotional processes—actually serving to reinforce the emotional experience of stress. In contrast, the more ordered and stable pattern of the heart’s input to the brain during positive emotional states has the opposite effect – it facilitates cognitive function and reinforces positive feelings and emotional stability. This means that learning to generate increased heart rhythm coherence, by sustaining positive emotions, not only benefits the entire body, but also profoundly affects how we perceive, think, feel, and perform. The good news is that you can use HRV biofeedback to train your body to be in a state of coherence. Just as the purpose of meditation is to practice mindfulness and the purpose of yoga is to align our body, breath and controlled movement, the purpose of HRV biofeedback is to train our emotional states to live in greater coherence with our physical body and emotions.
Coherence training is not that much different than putting on headphones and listening to music. There are a variety of sensors and applications available. Some of the sensors attach to the finger or clip on the ear while others are strapped to the chest. The applications range from an app on your smartphone to a more sophisticated and more expensive software that analyzes a variety of metrics onscreen.
The actual practice of HRV is simple. Heartmath has developed something called the “quick coherence” technique expressed in two simple steps:
Step One: Focus your attention in the areas of the heart. Imagine your breath is flowing in and out of your heart or chest area, breathing a little slower and deeper than usual. Suggestion: Inhale 5 seconds. Exhale 5 seconds.
Step Two: Make a sincere effort to experience a regenerative feeling such as appreciation or care for someone or something in your life.
Suggestion: Try to re-experience the feeling you have for someone you love, a pet, a special place, an accomplishment, etc. or focus on a feeling of calm and ease.
These are the simple guidelines for getting started. While implementing these steps a sensor attached to your earlobe or finger is calculating each R-R Interval (beat-to-beat) differences in your heartbeats. One of the profound differences between meditation and HRV biofeedback is that you are getting instantaneous feedback of where you are in the process. Meditation is obviously helpful yet its simplicity often confounds people with feelings of insecurity (Am I doing this right?). That guesswork is eliminated with HRV biofeedback. You know every five seconds where you are on the spectrum of coherence. If you are out of coherence you can adjust your breathing or your emotional focus slightly to bring yourself into coherence. If you are in coherence you begin to learn what your body feels like in these sustained moments of alignment. Once you know how your body responds to coherence training it is easier to move into coherence without the sensor when you feel stressed, angry, or sad.
As the soothing voice on the Inner Balance smartphone app encourages, “Don’t let the simplicity of these two steps fool you.”