What is Heart Rate Variability?
Most of the time, our heartbeat seems to be fairly consistent – almost like a clock, ticking along at a regular pace. That said, there are situations when it’s quite obvious that our heartbeat changes, for example in response to physical demands e.g., playing sport or running up the stairs, or if something creates a sense of fear and triggers our stress response. We notice the frequency of our heartbeat speeding up in the presence of physical or emotional demands and then slowing down when those things are no longer present.
However, it might not be obvious or even detectable to us, but there are slight fluctuations in the frequency of our heartbeat all the time – sometimes just fractions of seconds of variation that we couldn’t notice ourselves. For example, if a person has a heart rate of 60 beats per minute, the time intervals between each beat won’t be exactly the same. This fluctuation in heart rate - both the more obvious fluctuations and the indetectable ones - is termed ‘heart rate variability’ (HRV), so, we can say that heart rate variability is the measure of the variation of time intervals between each heartbeat.
This variation is controlled by our autonomic nervous system, the part of our nervous system that regulates many of our body functions in an automatic way, without the requirement of any conscious control on our part, such as changes in blood pressure, heart rate, respiration - including breathing, and the control of processes such as digestion. The autonomic nervous system has two main components:
1) the sympathetic branch that gears us up for action – adrenaline release leads to sympathetic activation which includes an increase in the speed and intensity of our heart rate and an increase in blood pressure to keep our muscles fed with blood and oxygen just in case they’re needed for action. Physically and psychologically, we feel pumped up and energised, ready to act. In situations of perceived threat, this sympathetic response is termed ‘fight or flight’ as it sets us up to fight or flee the potential threat to optimise our survival.
2) the parasympathetic branch that allows us to recoup our energy and resources when there’s no need for action, activating our natural relaxation and calming responses including the slowing of our heart rate, and lowering of our blood pressure. Termed ‘rest and digest’, in parasympathetic activation (i.e. when the parasympathetic state is activated), we feel physically and psychologically calmer as levels of anticipatory energy and arousal are reduced. The main nerve of the parasympathetic system, the vagus nerve acts like a brake, slowing our heart rate down whenever our parasympathetic nervous system activity is dominant.
As we can see, heart rate increases and decreases as we shift between sympathetic and parasympathetic dominance, and the shifts can be in response to the presence (or not) of physical and emotional stresses. This heart rate variability is a good thing as it is a reflection of our body’s capacity to adapt to whatever’s going on - if our heart rate is highly variable, this indicates that our body can adapt in the face of change – ramp up when it needs to and calm down when it’s appropriate. There’s also a routine shift from sympathetic to parasympathetic each time we inhale and exhale. This phenomenon is called respiratory sinus arrythmia - every time we breathe in our heart rate increases as the vagal brake of the parasympathetic nervous system is withdrawn, and every time we breathe out, the application of vagal brake slows our heart rate. So, we can also say that HRV is a measure of our autonomic balance.
Unfortunately, many of us are not in autonomic balance - we remain stuck in sympathetic activation for longer than is required or helpful and this is due to the nature of the kinds of stresses that come with modern day living. Sometimes we do need to act quickly e.g., to move out of the path or an oncoming car, however, most of the stresses we face today don’t require us to fight or flight anyone or anything yet this is the response we get – it’s like our nervous system hasn’t evolved in step with the evolution of the nature of the stresses we face. Many modern stresses are not physical stresses that are there one moment and gone the next like a tiger in our midst, instead, modern stresses tend to be more enduring, such as financial, emotional, relationship, health or education/work related worries.
Being stuck in this state means we experience very little parasympathetic dominance and the lack of variability in heart rate leads to less resiliency – which means our brain and body may struggle to manage changing situations simply because they’re not practiced at coming back to parasympathetic dominance i.e., our baseline, calm state.
Why is Heart Rate Variability important in Mental health? Research indicates a link between HRV and mood and anxiety. Depression, PTSD and a range of anxiety disorders including panic disorder, OCD, generalised anxiety disorder and social anxiety have all been observed to be linked with reduced HRV. This makes sense given a reduction in HRV indicates less adaptability in the face of change – and as outlined above, adaptability can be physical in nature, this is more obvious, but less obvious, adaptability in a psychological sense is also required if we’re to be flexible in response to changing states and situations. If something bothers us or makes us emotionally activated in some way, emotional health is reflected in our capacity to acknowledge those emotions and then come back to ground and return to our emotional baseline.
Reduced psychological flexibility and capacity for emotional regulation are both linked with reduced HRV. Social engagement also appears to be negatively impacted in association with reduced HRV, as well as underactivity of the pre-frontal cortex, the brain region that supports us with more conscious, deliberate, flexible responses. All of these features are commonly seen across depression, anxiety and PTSD related difficulties. For example, with anxiety disorders, we may find it difficult to disengage ourselves from worry and hypervigilance leading to a state of chronic activation of our sympathetic nervous system and reduced activation of our parasympathetic nervous system, and with this a reduction in HRV as our heart rate remains high due to being in this anxiety state. Researchers suggest that improving HRV may be a way to improve symptoms of depression, anxiety and PTSD.
How can we improve Heart Rate Variability? To improve HRV, we need to target the development of different states i.e., to practice activating our parasympathetic state as a way to balance out activation of the sympathetic state, this teaches our body adaptability. This can be done through therapy, in a top-down way i.e. exploring different ways of interpreting and responding to our experiences that calm emotional distress - feeling calmer emotionally can help calm us physically.
However, we can also improve HRV from the bottom up i.e., changing our physical state to influence our emotional state. Slowing our breathing activates the vagal brake of the parasympathetic system and slows the heart rate. Some research studies have explored breathing as a way to improve HRV finding that breathing at a slower pace can improve HRV. The slower rate of breathing allows for more variability in heart rate in comparison to breathing at a faster rate, and the rate that has been found most effective for improving HRV is around 6 breaths per minute. Some studies suggest that breathing with a longer exhale at a ratio of 1:2 inhale to exhale can further improve HRV. Other activities that involve longer exhales such as singing, chanting mantras and humming are all ways to practice breathing with a longer exhale.
Purposefully activating the parasympathetic nervous system is a helpful start, however we can go further than this if we are to improve HRV. Any activity that brings about periods of increased heart rate followed by periods of reduced heart rate supports the development of flexibility in our autonomic nervous system and increased heart rate variability, this could be any exercise that is punctuated with periods of rest. (If you have concerns about your heart, it’s a good idea to discuss exercise with your GP first).
The yoga practice that is taught as part of the Yoga Therapy 8 Week Course places a specific emphasis on improving HRV by sequencing the asana practice to include aspects that are geared toward purposefully raising the heart rate – with particular asana’s and breath practices – followed by periods of rest and practices geared toward purposefully reducing heart rate. This is one way the course supports participants toward improved emotional wellbeing via improved HRV.
So whilst it can be tempting to assume that we should never be in a ramped up state and being in such a state is bad for us, when we are activated in a way that is appropriate to the situation, and we practise calming ourselves, that provides practise for us to come back to our baseline, it helps us to develop resilience in our nervous system and this translates to greater emotional tolerance and psychological flexibility.
If you’re interested to explore this for yourself, feel free to get in touch to discuss how yoga therapy or an integration of some basic yoga therapy skills and psychotherapy may be helpful for you. You can read more about one-to-one work and the 8-week course here.
References
Chalmers, J. A., Quintana, D. S., Abbott, M. J. A., & Kemp, A. H. (2014). Anxiety disorders are associated with reduced heart rate variability: a meta-analysis. Frontiers in psychiatry, 5, 80. https://pubmed.ncbi.nlm.nih.gov/25071612/
Ge, F., Yuan, M., Li, Y., & Zhang, W. (2020). Posttraumatic stress disorder and alterations in resting heart rate variability: A systematic review and meta-analysis. Psychiatry investigation, 17(1), 9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992856/
Russo, M. A., Santarelli, D. M., & O’Rourke, D. (2017). The physiological effects of slow breathing in the healthy human. Breathe, 13(4), 298-309. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5709795/
Sgoifo, A., Carnevali, L., Pico Alfonso, M. D. L. A., & Amore, M. (2015). Autonomic dysfunction and heart rate variability in depression. Stress, 18(3), 343-352. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5709795/
Steffen, P. R., Bartlett, D., Channell, R. M., Jackman, K., Cressman, M., Bills, J., & Pescatello, M. (2021). Integrating breathing techniques into psychotherapy to improve HRV: Which approach is best?. Frontiers in Psychology, 12, 624254. https://www.frontiersin.org/articles/10.3389/fpsyg.2021.624254/full
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