FEATURE VIEWPOINTS HARNESSING HRV Heart rate variability (HRV) is gaining the attention of those interested in optimizing health and healing A BY DOUGLAS POOLEY AND KEITH THOMSON foundational com-ponent of our defining philoso-phy has been the recognition that: a) the nervous system controls all living functions, b) there are two com-ponents to the nervous system: sympa-thetic and parasympathetic, and c) that disease emerges when these two con-trolling systems are not in balance. Science is starting to catch up and rec-ognize the principles that we have always known to be true – a proper functioning nervous system is critical to health and well-being. Heart rate variability (HRV) is gaining the attention of health profes-sionals and the general public alike who are interested in optimizing health and healing, predicting long term morbidity, improving recovery and enhancing vitality. A healthy heartbeat still contains ir-regularities. For example, if your heart rate is 60 beats per minute, that does not mean that your heart beats once every second – or at one-second inter-vals like a clock. Rather, there is normal variation among the intervals between heartbeats. This per-beat variation is regulated by the nervous system and can even be felt at times: Place a finger gently on your neck and find your pulse. Normally you will notice that the longest interval takes place when you exhale, and the shortest interval occurs when you inhale. Heart rate variability measures how much variation there is in one’s heartbeat within a specific time frame. If the intervals between heart-beats are rather constant, this indicates that HRV is low. If the interval length varies, then HRV is high. and promote longer inter-beat inter-vals and thus elevate HRV. THE ROLE OF STRESS UNDERSTANDING THE AUTONOMIC NERVOUS SYSTEM To understand HRV we must under-stand the autonomic nervous system (ANS) and its relationship to heart rate. The autonomic nervous system regulates many important systems in the body, including heart rate, respi-ration rate and digestion. The auto-nomic nervous system has both a sym-pathetic (activation) and a parasympathetic (rest) branch. Heart rate variability is an indicator that both branches (the parasympathetic branch, in particular) are functioning. Factors such as stress can lead to overactivation or chronic activation of the sympathetic branch and decreased activation or even loss of the necessary braking activity of the parasympa-thetic branch. This imbalance in ANS activity will lead to elevated heart rate and lowered HRV, as it is the role of the parasympathetic nervous system to keep the nervous system in balance DR. DOUGLAS POOLEY graduated from the CMCC and has practiced in St. Thomas, Ont., for the past 39 years. He has represented the profession on national and provincial boards and has lectured nationally and internationally. DR. KEITH THOMSON is both a chiropractor and a naturopathic doctor. He is a former president of the College of Chiropractors of Ontario. He has been in practice in Peterborough, Ont., for almost 40 years. 20 Canadian Chiropractor December 2018 Stress plays a major role in the imbal-ance that can occur in the central nerv-ous system. When the body and mind experience stress, an emotional sensor will activate the sympathetic nervous system (SNS). This is commonly re-ferred to as the “fight or flight response.” If the parasympathetic nervous system does not engage to return the body to homeostasis and/or a sense of rest/digest then the result will be an unexpected release of adrenalin. Over time (and with chronic stress) this will lead to the breakdown of myocardial cells thus af-fecting blood flow to the heart. To review, HRV is regulated by the nervous system and measuring heart rate variability gives the practitioner valuable information about the nervous system by indicating if the nervous system is functioning in a more sympa-thetic (or “fight or flight” state), or if it is operating in a more balanced state with the help of parasympathetic activa-tion. One of the biggest modern-day causes of HRV and thus nervous system distur-bance is stress. In the February 2018 edition of Psychiatry Investigation, a study by Kim, Cheon, Bai, Lee and Koo entitled: “Stress and Heart Rate Varia-bility: A Meta-analysis and Review of The Literature” concludes: “The cur-rent neurobiological evidence suggests that HRV is impacted by stress and supports its use for the objective assess-ment of psychological health and stress.” www.canadianchiropractor.ca
Chiropractic + Naturopathic Doctor December 2018: Page 20
