Your heart’s beat is not uniform, meaning it doesn’t beat like the tick of a metronome (a heart rate of 60 beats per minute does not beat once every second.) This inconsistency in beats can be measured with what’s called a Heart Rate Variability (HRV.) In layman’s terms, this is the variability in time between heart beats.
Heart Rate Variability is becoming a crucial indicator of overall health and wellness as it reflects the balance between your sympathetic (fight or flight) and parasympathetic (rest and digest) nervous systems. A higher Heart Rate Variability will typically reflect a more dominant parasympathetic response, while a lower HRV, the opposite. Essentially, Heart Rate Variability is an indicator of one’s reactivity to stress, and ability to self-regulate.
There are many factors that have an effect on your Heart Rate Variability, as well as aspects of health that have a direct correlation to HRV.
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have the potential to increase parasympathetic activity and increase HRV.
Improvement to HRV can be achieved through regular aerobic exercise. This is achieved by increasing activity in the parasympathetic nervous system and decreasing activity in the sympathetic nervous system.
A study done on the elderly concluded that physical activity has a positive effect on HRV. Participants of the study who increased walking pace and/ or distance over a five year period had a more favourable HRV versus participants who decreased pace and/ or distance. Overtraining can however have an adverse effect on HRV, something that I experienced during my 10 mile a day for 2 weeks challenge.
Studies on a group of university students during a stressful exam period showed a decreased HRV when exposed to mental stress. Additionally, work stress has been found to be a common precursor to cardiovascular morbidity, and is also associated with a decreased HRV.
Though sleep is an extremely complicated phenomenon, some correlation between sleep quality and HRV has been discovered. A higher HRV is associated with greater sleep quality in healthy individuals, as well as lower incidences of insomnia, sleep apnea.
Unsurprisingly, depression is associated with a low HRV, as is general anxiety. As a side note, there’s evidence to suggest that mindfulness meditation enhances parasympathetic influences on the heart, therefore mitigating some symptoms of anxiety.
A low HRV, and dominant sympathetic response, increases the release of the stress hormone cortisol, which in turn causes heightened anxiety symptoms. This response can also explain how HRV is linked with threat perceptions. Someone with a high HRV may have reduced threat perception.
This pattern extends to more severe psychiatric disorders, such as bipolar disorder, PTSD, and schizophrenia. There’s evidence to suggest that a dysfunctional autonomic nervous system, and low HRV, have influence on these disorders (although it must be noted that other lifestyle factors may play a contributing role.)
Cardiovascular disease is the leading cause of death globally, killing 17.9 million people a year. A high HRV is often associated with greater cardiovascular health (and stress resilience), whereas a low HRV is linked to an increased risk of cardiovascular disease and death.
On a broader scale, autonomic imbalance has been found to be a major link between many disorders and conditions, to death and disease (including cardiovascular), with HRV being a key indicator of this potential imbalances.
HRV plays a role in sexual function as well. A higher HRV has been associated with greater sex drive, increased frequency of sexual engagement, increased frequency of orgasms, and increased rates of arousal in women, as well as a decrease in female sexual dysfunction. This can be attributed to HRV causing increased blood flow to the genitals, as well as improved emotional regulation.
HRV, being as complex as it is, requires a device to read and monitor. There are many consumer devices on the market that will give an HRV reading, though not all with total accuracy. Most popular wearable products will give a close to accurate reading when stationary, but start to decline in accuracy when movement increases. The most accurate way to measure HRV is with a chest strap, but these wrist and finger options offer a decent alternative:
It is important to keep in mind that HRV is a measure that is meant to be unique to the individual, so should not be compared with others, as high and low HRV readings are relative. Rather than focusing on a single reading, HRV trends should be tracked as they better reflect improvements in over health and wellness.
Though often times it’s a dominant sympathetic nervous system (“fight or flight”) that results in serious disease and ailments, a dominant parasympathetic nervous system (“rest and digest”) can have its share of problems. This could include a weakened immune system, deteriorated muscle tissue, slow reaction times, decreased motivation, and lack of basic survival instincts. For this reason, it is important that autonomic balance is achieved to maximize health and wellness.