Understanding Heart Rate Variability on Your Fitness Tracker—and Its Importance

For smartwatch users, heart rate variability (HRV) is a metric that has gained significant attention online and on social media, with many eager to track it for health insights.

Dr. Vivian Mo notes that the rise in HRV monitoring is fueled by the accessibility of wearable technology and apps like Whoop and Fitbit. She explains, "A quick Google search for 'heart rate variability' not only defines the term but also lists numerous devices capable of measuring it."

As Americans become more health-conscious and proactive in tracking their wellness, HRV has emerged as a valuable tool for assessing stress management and lifestyle improvements, according to Dr. Tamara Horwich.

Whether you actively monitor your HRV or have simply noticed it on your device, understanding its significance is key. Here’s what experts have to say about this trending health metric.

What Is Heart Rate Variability?

Dr. Mo describes heart rate variability as the variation in time intervals between heartbeats. For instance, while resting, your heart rate might average 60 beats per minute. However, upon closer inspection, the intervals between beats aren't perfectly uniform—sometimes they're slightly longer or shorter. This fluctuation is what defines heart rate variability.

Typically, individuals in their teens and 20s have an HRV ranging from 55 to 105 milliseconds, whereas those aged 60 and above usually experience lower variability, averaging between 25 and 45 milliseconds.

What Does Heart Rate Variability Tell You?

According to Dr. Theodore Maglione, Director of Electrophysiology at Robert Wood Johnson University Hospital, HRV provides valuable insights into your overall health. It can indicate how your body handles stress, the adaptability of your heart, your recovery status, and whether you're pushing yourself too hard.

HRV provides insights into your autonomic nervous system, which controls essential functions such as blood pressure and respiration.

The autonomic nervous system consists of two components: the sympathetic nervous system (SNS), responsible for the 'fight or flight' response and increasing heart rate, and the parasympathetic nervous system (PNS), which promotes 'rest and digest' functions and reduces heart rate. These two systems constantly interact to maintain balance in your body, and HRV reflects the dynamic interplay between them.

If your HRV is lower than usual over a 24-hour period, it may indicate prolonged activation of the sympathetic nervous system. Conversely, a higher HRV suggests greater parasympathetic influence, as noted by Dr. Horwich.

How to Compare HRV Results

According to Dr. Horwich, increased parasympathetic activity is beneficial for health. If your HRV over a 24-hour period is higher than your baseline, it generally signifies better health. Dr. Maglione adds that a higher HRV often indicates a relaxed and recovered state, commonly observed in individuals who are physically fit and practice effective stress management.

A low HRV may indicate an imbalance in your nervous system's regulatory mechanisms, according to Dr. Maglione. It often suggests that your body is under stress.

Dr. Horwich emphasizes that HRV is a complex metric. "It involves intricate mechanisms, various feedback loops, and multiple factors influencing heart rate variability," she explains. Due to this complexity, HRV is not commonly used by doctors as a primary health indicator, as more precise and objective measures are available.

What's a Normal HRV Range?

Dr. Carlos Macias, a cardiac electrophysiologist at UCLA Health, notes that HRV norms differ by age. "HRV typically declines with age, and the 'normal' range can vary widely," he states.

Which Lifestyle Factors Impact HRV?

HRV naturally declines with age, but factors like high stress, dehydration, excessive alcohol consumption, poor diet, lack of physical activity, and inadequate sleep can also lower it, according to Dr. Mo.

Conversely, HRV can improve when you adopt healthier habits such as stress management, balanced nutrition, regular exercise, proper hydration, reduced alcohol intake, and consistent sleep of seven to nine hours nightly. Dr. Mo notes that even a 65-year-old who maintains fitness and activity can achieve a higher HRV.

"Research shows that individuals who practice these healthy lifestyle behaviors often experience improved heart rate variability," she explains. "However, the exact physiological reasons behind this remain unclear."

Dr. Mo suggests these behaviors may influence the autonomic nervous system. Dr. Horwich supports this, stating, "Unhealthy eating, for instance, can trigger the sympathetic nervous system, and constant activation of this system is detrimental to overall health."

How Can You Track Your HRV?

Dr. Horwich explains that the most precise method to monitor heart rate variability is through a continuous electrocardiogram (EKG), which measures the electrical activity of your heart. To track heart rhythms over time, a cardiologist may use a Holter monitor or patch, allowing for EKG readings even during daily activities.

Regarding smartwatches, Dr. Horwich notes that their HRV measurements rely on wrist pulse detection, making them less accurate than chest-based EKGs. However, Dr. Maglione adds that fitness trackers can still help identify HRV trends over time. "Focus on overall patterns rather than single readings. A consistent decline in HRV may indicate the need to reduce stress or exertion," he advises.

If you observe significant changes in your HRV, consulting a doctor is advisable. While tracking HRV on your device, avoid overstressing about individual readings, as they may not always be entirely accurate or comprehensive. Dr. Maglione emphasizes that HRV can vary for numerous reasons, so it’s best to monitor trends, discuss concerns with your doctor, but avoid unnecessary worry.

How Much Attention Should You Pay HRV as a Health Metric?

While adopting healthy habits is encouraged, using HRV as a primary health goal may not always be practical or motivating. Dr. Mo points out that numerous factors influence HRV, and "it’s challenging to control all these variables solely to improve heart rate variability."

Focusing on healthy habits and evaluating their effects through other indicators—such as improved endurance during exercise or reduced anxiety and stress levels—can be more fulfilling.

Dr. Mo emphasizes that enhancing a patient’s diabetes, cholesterol, or blood pressure already indicates better overall health, making it unnecessary to prioritize HRV improvement separately.

It’s important to note that HRV isn’t the sole indicator of cardiovascular health. Dr. Maglione advises, "Strive for a healthy lifestyle by limiting excessive alcohol, caffeine, and smoking."

How to Choose the Best Heart Rate Variability Monitors

Dr. Macias recommends selecting HRV monitors that offer continuous heart rate tracking for accuracy. Devices like the Apple Watch, which rely on intermittent readings, may not be as precise as medical-grade monitors or chest-strap models.

For most individuals, wearable devices like the Apple Watch, Oura Ring, WHOOP, Fitbit, and Garmin Forerunner, when used consistently over weeks, provide valuable insights into HRV trends and help identify the need for lifestyle adjustments.

Frequently Asked Questions

• Should I worry if my HRV is low?

  "A low HRV isn’t an immediate cause for alarm but signals areas for improvement, such as better physical conditioning," explains Dr. Macias. "It’s advisable to consult your doctor and consider starting an exercise regimen."

• Who can benefit most from tracking HRV?

  According to Dr. Macias, while no specific group benefits exclusively from HRV tracking, those with low HRV can use it to monitor how lifestyle changes positively impact their variability.