Do you feel sometimes you get “stuck” in fight or flight mode and can’t relax or lower stress levels? Heart Rate Variability (HRV) is the variation in time between consecutive heartbeats and, fascinatingly, is an indicator that can tell us more about the extent this “getting stuck” is happening and provide real-time feedback on how well our body is managing stress and recovery. By tracking it over time we can learn how to take more control of taking ourselves into a “rest & recover” state which has benefits for health, resilience, and overall well-being.
Firstly: How is our nervous system organised?
Our autonomic nervous system controls the automatic functions of your body such as breathing, heart rate, sweating and immune responses. It’s always active, based in a network of nerves outside the brain and spinal cord connecting them to our internal organs, working behind the scenes to keep us balanced and responsive to our environment.
It is divided into two: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). These two systems maintain a dynamic equilibrium and using HRV we can measure the extent to which they are balanced (autonomic balance) or if one is prevailing.
The Sympathetic Nervous System
The sympathetic nervous system is the body’s "fight or flight" system. When you face a stressor; physical, emotional, or psychological, the SNS activates to prepare your body to respond resulting in:
Increased heart rate
Dilated pupils
Elevated blood pressure
Reduced digestive activity
Heightened alertness
These changes are designed to enable you to act quickly and effectively in the face of perceived danger. While this response is essential for survival, prolonged activation of the SNS due to chronic stress can lead to negative health outcomes, such as hypertension, anxiety, and cardiovascular issues.
The Parasympathetic Nervous System
In contrast, the parasympathetic nervous system is often referred to as the "rest and digest" system. It promotes relaxation and recovery by counteracting the effects of the SNS. Activation of the PNS leads to:
Slower heart rate
Increased digestive activity
Constriction of pupils
Lower blood pressure
Enhanced restoration of energy reserves
The PNS helps the body return to a state of calm after a stressor has passed, fostering recovery and long-term health.
Heart Rate Variability: A window Into autonomic balance
Heart rate variability (HRV) is the variation in time between consecutive heartbeats, and it serves as an indicator of the interplay between the SNS and PNS. Unlike a steady metronome, a healthy heart exhibits variability in its rhythm, reflecting the body’s adaptability to internal and external stimuli and the influence of both the SNS and PNS.
High HRV: A high HRV indicates a well-balanced and adaptable autonomic nervous system ie good autonomic balance, with strong parasympathetic activity as well as sympathetic activity. It suggests that the body can efficiently recover from stress and adapt to changing circumstances. Periods of relaxation after stressors lead to parasympathetic activity predominating
Low HRV: During periods of stress or physical exertion, sympathetic activity takes over from parasympathetic activity, reducing HRV. A persistently low HRV therefore often signals dominant sympathetic activity, chronic stress, or reduced adaptability with little parasympathetic activity and recovery and therefore poor autonomic balance. The body is effectively “stuck” in a “fight or flight” state. A long term low HRV is often associated with conditions like anxiety, depression, and cardiovascular disease.
Measuring HRV
HRV can be measured using a variety of devices, ranging from medical-grade equipment to consumer-friendly wearables, like fitness trackers and smartwatches which have made HRV monitoring more accessible recently.
Garmin watches’ "Body Battery" metric, or the WHOOP and Oura Ring use HRV alongside other factors such as stress and activity levels to provide an overall assessment of energy reserves. By monitoring HRV at a point in time, we gain insight into how balanced your autonomic nervous system is more active at that time. By tracking HRV trends over time, you can better understand how your lifestyle and stress levels impact how balanced your sympathetic and parasympathetic systems are, your autonomic balance.
Why HRV matters
HRV is more than just a number; it’s a meaningful measure of physiological resilience and health. Research shows that higher HRV is associated with better cardiovascular health, improved emotional regulation, and greater overall well-being.
How to improve HRV and support autonomic balance
Build and nurture a way to relax: Activities like deep breathing, yoga, massage and mindful/meditative activities stimulate the parasympathetic nervous system, increasing HRV.
Regular exercise: Moderate aerobic exercise enhances overall cardiovascular fitness and HRV.
Prioritise sleep: Quality sleep supports autonomic balance and higher HRV.
Healthy nutrition: A balanced diet reduces inflammation and supports overall health.
Stress management: Techniques to control stress including time spent outside and in nature can lower chronic SNS activation.
Conclusion
The sympathetic (fight or flight) and parasympathetic (rest & digest) nervous systems are two sides of the same coin, each playing a vital role in maintaining our physical and emotional health. Heart rate variability acts as a window into this balance, providing real-time feedback on how well our body is managing stress and recovery. By understanding and optimising HRV, we can take proactive steps toward better health, resilience, and overall well-being.
Comments