Heart Rate Variability
by Allison Deckel
Yoga East Teacher Training 2022
Our respiratory system syncs with our heart
through a process called respiratory sinus arrhythmia (RSA). When we inhale, we
activate our sympathetic nervous system increasing our heart rate. When we
exhale, we activate our parasympathetic nervous system, decreasing out heart
rate. The more robust the system the more variation there is between heart rates.
The higher the HRV is, the more effective we are at managing our reactions to
upsetting events and thinking through our best responses in a calm manner.
(Cleveland Clinic, 2021).
When
the heart is unable to fluctuate in response to breathing, this will have a
negative impact on how the body reacts to stress. Specifically, low heart rate
variability increases the likelihood for
medical illness such as heart disease and cancer, as well as psychological
problems such as depression and Post Traumatic Stress Disorder (PTSD). Low HRV makes it more difficult to manage
emotions and think through how we want to respond in the most effective way to
stressors (Van der Kolk, 2014).
What impacts heart rate variability? There is a
growing body of influence that early childhood trauma changes the brain and
leads to various poor health outcomes, including diminished HRV. The CDC-Kaiser
Permanente adverse childhood experiences (ACE) study is one of the largest
investigations of how early childhood trauma effects physical and mental health
outcomes. The findings indicated that as
the number of ACEs increase, the risk for health problems later in life also increase
(CDC, 2021). In the
book, The Body Keeps the Score, the author, Bessel Van Der Kolk, MD, outlines
how repeated exposure to traumatic events causes an over stimulation of the Autonomic Nervous System (ANS), resulting in poor HRV.
Yoga has been shown to have positive effects on
physical and emotional well-being. Understanding this, Dr. Bessel Van Der Kolk
and his team at the Trauma Center in Boston, MA, decided to study if regular
yoga practice increased heart rate variability specifically. They selected
thirty-seven women with severe trauma histories who had tried traditional
psychotherapy but had not received much improvement. Half of the women took the
yoga class, while the other half participated in dialectical behavior therapy (DBT),
which is a well-established type of therapy that focuses on mindfulness. Their
classes consisted of breath work (pranayama) and classic poses, with an
emphasis on mindfulness, or being aware of the sensations that are happening
during class within the body and in the mind. The results indicated that HRV
improved with the yoga participants and did not change with the other group.
These findings motivated them to incorporate yoga class as a treatment modality
at their trauma center.
There are many ways to help students connect with
their breath in a yoga class. A commonly used technique that is simple and
effective is coherent breathing. In
coherent breathing, the goal is to bring awareness to, as
well as, extend the length of the breath itself. Students take a comfortable seat, keeping a
straight spine, and asked to inhale through the nose for 6 counts and exhale through
the nose for 6 counts. One may have to start with 4 counts and with practice
work up to the full 6 counts. This is usually done at the beginning of class to
bring awareness throughout the practice (Verywell Mind, 2020).
In the journal, Applied Psychophysiology and Biofeedback,
a comprehensive search
of multiple databases was conducted and all studies that reported a measure of
HRV associated with any yoga practice were included. Studies were categorized
by the study design and type of yoga practice. A total of 59 studies were reviewed
involving a total of 2358 participants. Most studies were performed in India on
relatively small numbers of healthy male yoga practitioners during a single
laboratory session. Of the reviewed studies, 15 were randomized controlled
trials. The reviewed studies suggest that yoga can improve HRV. Regular yoga
practitioners were also found to have increased vagal tone at rest compared to
non-yoga practitioners. However, they were unable to draw any firm conclusions
about yoga and HRV as most studies were of poor quality, with small sample
sizes and insufficient reporting of study design and statistical methods. While
there is convincing evidence that yoga does improve HRV, more quality studies
are needed to state this definitively (Posadzki,
Kuzdzal, Lee, & Ernst, 2015).
References:
Heart Rate Variability (HRV). Cleveland Clinic, 2021, retrieved from http://my.clevelandclinic.org/health/symptoms/21773-heart-rate-variability-hrv
Stress effects on the body. American Psychological Association, 2018 retrieved from https://www.apa.org/topics/stress/body
Violence Prevention. Centers for Disease Control and Prevention, 2021 retrieved from
https://www.cdc.gov/violenceprevention/aces/about.html
Bessel Van Der Kolk, MD (2014). The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. Penguin Books.
Posadzki, P., Kuzdzal, A., Lee, MS., Ernst, E., 2015. Yoga for heart rate variability: A systematic review and meta-analysis of randomized controlled trials. Applied Psychophysiological Biofeedback, 40, 239-249.
Health. John Hopkins Medicine, 2022, retrieved from https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/electrocardiogram
An Overview of Coherent Breathing. Verywell Mind, 2020 retrieved from
https://www.verywellmind.com/an-overview-of-coherent-breathing-4178943
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