man checking metrics on watch

The One Training Metric You Aren’t Tracking (But Should)

Heart rate variability is considered one of the best objective metrics for physical fitness and determining your body’s ability to perform. Here’s how to improve it.

Fast Facts

  • HRV is an important metric that can help you tune into your overall health and performance. 
  • Low HRV could be a sign you’re sick, stressed, or in need of rest. 
  • Stress, diet, hydration, fitness, and overall health all play a role in your HRV. Improve these areas to see a lift in long-term HRV trends. 

Elite athletes have long turned to heart rate variability as a go-to way to track performance. Heart rate variability (HRV)—the differences in the time interval between heartbeats—helps athletes train smarter, recover better, and perform more consistently.

Advances in technology that were once reserved for pro athletes are now available to all, and the trickle down means you can tune into your body’s readiness to perform.

“It used to require a trip to your doctor’s office to measure HRV,” says Jack Jeng, M.D., Chief Medical Officer at Hone Health. “Thanks to new wearable technology we can now monitor HRV from the comfort of home, providing more insights into our health.”

Here’s everything you need to know about HRV, and how to track it so you can perform better, too.

What Is HRV?

Heart rate variability is the variance in time between successive heartbeats, which fluctuate slightly from beat to beat.

For example, if your heart rate is 60 beats per minute, your heart isn’t actually beating once every second. Within that minute there might be 0.9 seconds between two beats and 1.1 seconds between the next two.

It is believed that the greater the variability is, the more “ready” your body is to execute at a high level at any given moment.

“Low heart rate variability may show your body is less resilient to stress.”

Why Does HRV Matter?

Even though HRV is determined by small fluctuations in time, long-term trends could have big implications for your emotional state, physical health, and athletic performance (1).

Your body handles all kinds of stimuli every day. However, persistent instigators—like chronic stress, poor sleep, unhealthy diet, dysfunctional relationships, isolation, or lack of exercise—can lead to trends of low HRV.

“Low heart rate variability could be a sign of current or future health problems because it may show your body is less resilient to stress and might struggle to respond to changing situations,” says Jeng.

What Controls HRV?

Although your heart rate variability is determined by measuring your heartbeat, it’s actually mediated by your nervous system. Your autonomic nervous system (ANS) controls involuntary physiological functions like heart rate, blood pressure, breathing, and digestion without you giving them a second thought.

The ANS is divided into two components: the sympathetic and parasympathetic. These branches work in tandem to respond to your body’s needs.

Sympathetic vs. Parasympathetic

Your sympathetic nervous system, often called “fight or flight”, increases your heart rate and blood pressure in response to things like stress and exercise.

Your parasympathetic nervous system, also called “rest and digest”, causes a decrease in heart rate and increases your body’s ability to relax.

When your ANS is balanced, these two systems are responsive and work together to send your body signals. Whether you’re awake or asleep, calm or stressed, working out or lounging on the couch, your heart has to be able to react quickly to changes in your environment.

Your sympathetic nervous system tells your heart to beat faster and your parasympathetic nervous system tells your heart to beat slower. This causes fluctuations in your heart rate: HRV.

How to Track HRV

There are many ways to track HRV. The gold standard is to get an electrocardiogram in your doctor’s office. But in recent years, many apps and fitness trackers offer similar features to make tracking HRV trends more convenient and practical.

Popular HRV trackers include:


These trackers might be more functional for everyday wear, but current research suggests chest strap monitors are more accurate when measuring heart rate (2).

Popular manufacturers of chest strap monitors include:


What Can Your HRV Tell You?

“Low heart rate variability could mean your sympathetic nervous system is in overdrive,” says Jeng. “Increased sympathetic activity promotes inflammation and chronic inflammation has been linked to many diseases, from diabetes to heart attacks and strokes.”

Studies have shown that HRV and stress are directly related (3). Low HRV is also associated with an increased risk of developing a heart arrhythmia known as atrial fibrillation (4, 5). Other conditions linked to low HRV include diabetes (6) and depression (7). Low heart rate variability has even been associated with the risk for sudden cardiac death (8) and all-cause mortality (9).

Low HRV can be an indication that your body is working hard (maybe you’re fatigued, dehydrated, stressed, or sick) and needs to recover. Over long periods of time, low HRV may mean you have less resources for exercising, socializing, or performing at work.

Why HRV is a Sign of Fitness

Think about a cornerback before a play: alert, dynamic, and ready to move wherever the ball goes. You want your heart to be similarly adaptable. A high HRV is a sign that your body can respond to a given situation in a moment’s notice.

Studies have shown that high cardiorespiratory fitness is a strong predictor for high HRV (10, 11), which is why elite athletes generally have a higher HRV than the rest of us.

But even athletes experience ebbs and flows in HRV. For example, after high exertion activities like sprints or HIIT training, it’s normal for your HRV to take a dip. With rest your HRV will rise, letting you know your body is ready to push again.

What HRV Training Entails

Many studies have shown heart rate variability can be a valuable tool for improving your fitness and performance (12, 13). HRV-guided training means that rather than sticking to a predetermined workout schedule, you modify the intensity and duration of your physical activity based on your heart rate variability.

When your HRV is high, your body is prepared to take on a greater workload like sprinting. When it’s low, it’s a sign to cut back and give your body much needed rest. By adjusting your exercise based on HRV, you can train smarter and more efficiently.

HRV can be used to monitor how well your body is responding to your workout program (14). One study found that when done properly endurance athletes were able to use HRV to efficiently improve their VO2 max (15).

What Is a Good HRV Rate?

Unfortunately, heart rate variability fluctuates greatly throughout the day, from one day to the next, and from one person to another. So, determining a “good” or “normal” HRV is more complicated than it appears.

In general, HRV decreases with age (16), males tend to have slightly higher HRV than females (although a more gradual reduction occurs in females after their sixties) (17), and elite athletes usually have higher HRV than the general population.

But these are just generalizations and there are plenty of fit people who have low HRV. Which is why what constitutes a healthy HRV differs from person to person.

Rather than comparing your heart rate variability to others, it’s more helpful to follow your own HRV trends. “If you track your HRV trends over time and notice an acute drop, this could be an indicator that you are overtraining or starting to get sick,” says Jeng. “A recent study showed changes in HRV could signal the onset of COVID-19 days before a positive test result.”

“If your HRV suddenly drops, you might be overtraining or getting sick.”

What HRV Trends Matter

Both short-term and long-term HRV trends can be helpful to follow, but if you’re looking to improve your overall health you should be monitoring your long-term trends to see how your lifestyle changes are influencing your HRV.

For example, if you’re making healthy choices like drinking more water, exercising, eating a balanced diet, or getting better sleep, you should see a gradual increase in your average heart rate variability over several months.

Similarly, a downward trend in your HRV over several days is worth paying attention to. It could be a sign you’re stressed, training too hard, not sleeping enough, eating poorly, or not hydrating properly. Acute illnesses, like the flu or COVID, can also lead to a drop in HRV.

What Is a Good HRV While Sleeping?

Nighttime is one of the best opportunities to track your heart rate variability.

By measuring your HRV during the day, you’re capturing your body’s response to fleeting changes (food, social interactions, temperature fluctuations, etc.), which can impact your HRV readings.

At night, your body is in a consistent state, without any confounding variables. To understand your chronic physiological state, the best time to measure HRV is while you sleep.

Like any time of day, your sleeping HRV is individual to you. So, it’s best to focus on your trends rather than comparing yourself to others.

Factors That Affect HRV

Your heart rate variability is influenced by a variety of inputs which fluctuate throughout the day and from day to day. These include physiological factors, diseases, and external factors.

Physiological Factors

A handful of physiological factors that you have little control over (with the exception of your cardiovascular fitness and circadian rhythm to a certain degree) affect your HRV. These factors include:

  • Age (16)
  • Gender (17)
  • Cardiovascular fitness
  • Circadian rhythm (18)


It’s important to note there are outliers. For example, if you’re male, it doesn’t mean you’ll always have a higher HRV, but men do tend to have higher HRV than women.


Many studies have examined the effects of various diseases on HRV, and it was found to be lower in people who were suffering from certain diseases when compared to healthy people. Some of these diseases include:

  • Diabetes (6)
  • Heart disease (19
  • Interstitial lung disease (20)
  • Kidney dysfunction (21)
  • Depression (7, 22)


External Factors

There are a variety of external factors that can lead to changes in HRV due to your autonomic nervous system’s response to your surroundings. If regularly exposed to these elements, it may lead to chronic trends of low HRV. 

  • Extreme temperatures (23)
  • Noise (24)
  • Acute pain (25)
  • Overtraining (26)

When to Worry About Your HRV

In general, an abnormal HRV reading isn’t cause for concern, but it can be a sign of current health problems or issues down the road. It’s important to keep in mind that your heart function is complex and goes beyond rate and rhythm.

“Measuring your HRV can provide valuable information if you’re working on improving your fitness or overall health,” says Jeng. “However, these devices do not replace seeing your doctor, especially if you have concerns about your heart or have an underlying heart condition.”

While wearable devices and apps that track your heart rate variability are becoming increasingly effective at metrics tracking, at-home devices aren’t as accurate or provide as much information as an electrocardiogram performed at your doctor’s office.

More advanced diagnostic tools are often used to evaluate for heart problems, such as echocardiograms or angiograms. A healthcare provider is still the most qualified person to assess your heart and determine if there’s cause for concern.

How to Improve HRV

To improve your heart rate variability, focus on improving your physical and mental health—both are vital to HRV. Here are a few specific factors to narrow in on.

Train Intelligently

Don’t overdo workouts. Give your body the opportunity to recover by taking rest and recovery days, and reduce the intensity of your sessions if your HRV is trending low.

Stay Hydrated

Better hydration means better circulation, helping your blood deliver oxygen and nutrients to your body.

Limit Alcohol

One study found that moderate to heavy alcohol use can negatively impact your HRV, and it can take over 4 months of abstinence for heavy drinkers to improve their resting HRV (27). It’s a good reason to enjoy drinking in moderation.

Follow a Healthy Diet

Poor nutrition has adverse effects on HRV, as well as eating at unexpected times. Eat a healthy diet on a consistent schedule.

Get Quality Sleep

Consistently getting high-quality sleep can improve your HRV. To improve your sleep hygiene, try following a schedule of going to bed and waking up at the same time every day.

Be Consistent

Your HRV improves when your circadian rhythm is aligned with your lifestyle. Get your body on a consistent sleeping and eating schedule—your body is more efficient when it knows what’s coming.

Try Heart Rate Variability Biofeedback Training

By using a method called heart rate variability biofeedback training, you can improve your stress and anxiety—as well as your HRV—by taking slow and controlled breaths (1). One study found that breathing six times per minute for five minutes twice a day while seated in a quiet home environment can have benefits like reducing anxiety (28).

The Bottom Line

HRV can provide invaluable insight into your overall health and fitness, but it’s only useful if you track your trends long-term. There are many ways to improve HRV like eating healthier, getting better sleep, and reducing stress. Focus on a holistic approach to improve your HRV over time. 

1. Lehrer, P. et al (2020). Heart Rate Variability Biofeedback Improves Emotional and Physical Health and Performance: A Systematic Review and Meta Analysis.
2. Cosoli, G. et al (2020). Wrist-worn and chest-strap wearable devices: Systematic review on accuracy and metrological characteristics.
3. Kim, H. et al (2018). Stress and Heart Rate Variability: A Meta-Analysis and Review of the Literature.
4. Habibi, M. et al (2019). Resting Heart Rate, Short-Term Heart Rate Variability and Incident Atrial Fibrillation (from teh Ethnic Study of Arthlersclerosis (MESA)).
5. Agarwal, S, et al (2017). Cardiac Autonomic Dysfunction and Incidence of Atrial Fibrillation: Results From 20 Years Follow-Up.
6. Benichou, T. et al (2018). Heart rate variability in type 2 diabetes mellitus: A systematic review and meta-analysis.
7. Benichou, T. et al (2018). Heart Rate Variability in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis.
8. Maheshwari, A. et al (2016). Low Heart Rate Variaility in a 2-Minute Electrocardiogram Recording is Assoiated with an Inreased Risk of Sudden Cardiac Death in the General Population: The Arthlersclerosis Risk in Communities Study. 
9. Fang, S. et al (2019). Heart Rate Variability and Risk of ALl-Cause Death and Cardiovascular Events in Patients with Cardiovascular Disease: A Meta-Analysis of Cohort Studies.
10. Chen, L. et al (2020). Cardiorespiratory Fitness, Adiposity, and Heart Rate Variability: The CARDIA Study.
11. Kiviniemi, A. et al (2017). Fitness, Fatness, Physical Activity, and Autonomic Function in Midlife.
12. Manresa-Rocamore,A. Et al (2021). Heart Rate Variability-Guided Training for Enhancing Cardiac Vagal Modulation, Aerobic Fitness, and Endurance Performance: A Methodological Systematic Review with Meta-Analysis.
13. Perez-Guido, M. et al (2021). Can HRV Biofeedback Improve Short-Term Effort Recovery? Implications for Intermittent Load Sports.
14. Phoemsapthawee, J. et al (2019). Heart rate variability responses to a combined exercise training program: correlation with adiposity and cardiorespiratory fitness changes in obese young men.
15. Gallegos, A. et al (2020). HRV-based Training for Improving VO2 Max in Endurance Athletes. A Systematic Review and Meta-Analysis.
16. Kumral, D. et al (2019). The age-dependent relationship between resting heart rate variability and functional brain connectivity.
17. Swan, C. (2020). The Influence of Age and Gender on Heart Rate Variability.
18. Riganello, F. et al (2019). Circadian Rhythms and Measure of CNS/Autonomic Interaction.
19. Zhang, L. et al (2020). Sleep heart rate variability assists the autonomic prediction of long-term cardiovascular outcomes.
20. Rigatto, K. et al (2018). Parasympathetic Nervous System withdrawal in patients with Interstitial Lung Disease but not in COPD patients.
21. Chou, Y. et al (2018). Heart rate variability as a predictor of rapid renal function deterioration in chronic kidney disease patients.
22. Dell’Acqua, C. et al (2020). Reduced heart rate variability is associated with vulnerability to depression.
23. Tang, M. et al (2021). The acute effects of temperature variability on heart rate variability: A repeated-measure study.
24. Aarbaoui, T. et al (2019). The short-term association between exposure to noise and heart rate variability in daily locations and mobility contexts.
25. Forte, G. et al (2022). Heart Rate Variability and Pain: A Systematic Review.
26. Singh, N. et al (2018). Heart Rate Variability: An Old Metric with new Meaning in the Era of Using mHealth technologies for Health and Exercise Training Guidance. Part Two: Prognosis and Training.
27. Ralevski, E. et al (2019). Heart rate variability in alcohol use: A review.
28. Deschodt-Arsac, V. et al (2018). Effects of heart rate variability biofeedback training in athletes exposed to stress of university examinations.