Kristin Haraldsdottir, PhD
Exercise & wellness researcher
Heart rate variability (HRV) is one of the best kept secrets to managing your overall health; the variation between your heart beats is a strong indicator of your body’s general readiness, adaptability, and wellbeing. It can reveal the presence of heart conditions, anxiety, and other potential health problems. In fact, regularly tracking HRV is now used by everyone from elite athletes tracking their recovery to doctors assessing patients’ risk profile for certain diseases.1
What Is Heart Rate Variability (HRV)?
HRV measures the amount of time between successive heart beats in milliseconds (ms) and is calculated using the root mean square of successive differences (RMSSD) to determine the degree to which that time fluctuates.2 Your heart doesn’t beat at exactly perfect intervals.
In the example below, this person’s average heart rate is 76 beats per minute, but the first two beats were .84 seconds apart (839 ms) and the next two beats were .79 seconds apart (789 ms).
These tiny fluctuations in time between beats are the result of the autonomic nervous system keeping our bodies at equilibrium. The autonomic nervous system is responsible for anything the body does involuntarily and automatically to survive, from breathing, to digesting food, to urinating. It’s divided into two branches: the parasympathetic nervous system, also known “rest and digest” because it activates when you’re calm, and the sympathetic nervous system, also known as “fight or flight” because it activates in times of stress or perceived danger.
Working behind the scenes, these two systems operate in tandem to keep the body at equilibrium by making necessary changes to heart rate, blood pressure, perspiration, etc. Essentially, they make sure that your body can respond to stress at a moment’s notice and is able to relax when rest is needed.
Why Is a Higher HRV Desirable?
Greater variability between heart beats generally means that the body is ready to quickly adjust and react to stress. It indicates balance between the two branches of the nervous system so the body can respond to a “fight or flight” input from the sympathetic system as well as a “rest and digest” input from the parasympathetic system.
Additionally, research shows that people with higher activity from the parasympathetic nervous system may experience lower stress, more rest, generally better health, and a higher HRV. Conversely, lower heart rate variability can be a sign of current or future health problems because it shows your body is chronically stressed and struggles to handle changing situations.
As is the case with many other biometrics, everyone’s baseline HRV will be different, so it’s more important to understand your own HRV baseline and trends than compare yours to someone else’s.
What Affects HRV in Women?
HRV is affected by many sociological and biological factors including sleep, physical activity, body composition, cholesterol, and diet. In addition, cyclical hormonal changes within women’s bodies – including the menstrual cycle, menopause, and pregnancy – have a significant impact on HRV. Specifically, when progesterone decreases it activates the sympathetic system, so there’s an involuntary increase in resting heart rate and decrease in HRV at that time.
There is much to be learned about hormonal impacts to HRV, but generally we see the following trends:
- Reproductive hormones, particularly estrogen and progesterone, affect cardiovascular function, causing HRV to be higher during the proliferative phase of the menstrual cycle (the first ~14 days).4
- HRV progressively drops throughout pregnancy, then sharply increases during the post-partum period. HRV could be used to detect pregnancy complications or abnormalities, such as gestational hypertension or pre-eclampsia.6
- Pre-menopausal women tend to have higher HRV; therefore, pre-menopausal women have a lower risk of cardiovascular disease than men similarly aged men, despite women having a greater risk of cardiovascular disease more generally. 3
- HRV declines in women during menopause in response to declines in estrogen and progesterone5 resulting in post-menopausal women with low HRV more likely to develop heart disease than those with higher HRV.1
What Are the Benefits of Tracking HRV?
Historically HRV was difficult to measure because it required specialized equipment, so many women weren’t aware of their HRV. Today, wearables and other products that measure HRV at home are much more accessible, so it’s never been easier to understand and track your HRV.
Tracking your HRV helps you understand your natural baseline trends, so when there are deviations from that trend you can act. Small changes, including being more intentional about getting good sleep or exercising, can help you manage HRV.
Consistently low HRV is a potential risk factor for cardiovascular disease among women, because it’s an indicator of higher overall stress and lower wellbeing. Given that heart disease is the leading cause of death among women, regularly tracking HRV can allow women to make changes to increase HRV and help reduce the risk of developing cardiovascular disease.7
How Can You Keep a Healthy HRV?
- Sleep: Getting more and better quality sleep is one of the most impactful things you can do to increase HRV, because with more sleep, your body is more rested and more prepared to respond to stress.
- Physical activity: Increasing fitness, maintaining a healthy weight, and good heart health can increase HRV and prepare the body to respond to stress.
- Hydration: When we don’t drink enough water and become dehydrated, HRV typically declines.8
- Alcohol: Consumption of alcohol has an immediate and direct impact on lowering HRV.9
- Diet: A healthier diet contributes to a healthier cardiovascular system and therefore a higher HRV. HRV can improve in response to healthy levels of blood glucose and cholesterol from a nutritious diet.10
- Time in nature: Spending time outside is associated with increases in HRV.11
- Stress: Low HRV is associated with high mental stress, depression, and anxiety.12
Though HRV is in part the result of your biological makeup, these behavior changes can positively impact HRV and improve overall health. There’s still much to learn about HRV and how it relates to your nervous system but understanding your natural baseline and monitoring for fluctuations can be a very helpful input in managing your overall health.
- Baig https://pubmed.ncbi.nlm.nih.gov/36282885/
- Schaffer https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624990/
- Koenig https://pubmed.ncbi.nlm.nih.gov/26964804/
- Brar https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4625231/
- Ramesh https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9127980/
- Sarhaddi https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9206203/
- CDC https://www.cdc.gov/heartdisease/women.htm
- Young 2019 https://www.nature.com/articles/s41598-019-52775-5
- Karpyak https://pubmed.ncbi.nlm.nih.gov/24117482/
- Young 2018 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882295/
- Scott https://pubmed.ncbi.nlm.nih.gov/33048361/
- Kim https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900369/