What is HRV?

With the heart serving as the body’s metronome—and its disrepair and dysfunction the number one cause of death worldwide—it’s all too important to ensure the heart remains healthy. Not only to maintain your physical fitness, but also to support your mental well-being and overall health. 

Gone are the days when a heart’s health was solely measured using a stethoscope. Now, we know that reading between the beats can offer significant insight into the heart’s health, with the changes in this measurement, also known as heart rate variability, providing a way to monitor cardiovascular health, mental well-being, and physical fitness. 

What is HRV and what can it tell you?

Heart rate variability (HRV) refers to the variation in timing between heartbeats. It is a key measure of how well your body is able to respond to stress, recover from physical exertion, and maintain heart health. A higher HRV is typically a sign of better cardiovascular fitness, while a lower HRV may indicate stress or potential health issues.

Knowing the insights offered by HRV, it’s clear that it can highlight concerns that may otherwise go unnoticed, worsening someone’s health while no one is the wiser. However, HRV fluctuations are often imperceptible except with specialized devices, highlighting the importance of these tools for accurately measuring subtle changes in heart function. Having a quick and convenient way to evaluate HRV offers a way to monitor both physical and mental health.

Understanding HRV

Heart rate variability (HRV) is a fascinating and complex physiological phenomenon that measures the variation in the time interval between consecutive heartbeats, typically in milliseconds. Unlike heart rate, which counts the number of beats per minute, HRV focuses on the subtle fluctuations in the timing of each heartbeat. These fluctuations are influenced by a myriad of factors, including respiration, exercise, hormonal reactions, metabolic processes, cognitive activities, stress, and recovery.

HRV serves as a window into the autonomic nervous system, which controls many of the body’s involuntary functions. By analyzing HRV, we can gain insights into how well the autonomic nervous system is functioning and how it responds to various internal and external stimuli. This makes HRV a valuable non-invasive indicator of overall autonomic nervous system activity and health.

The role of the autonomic nervous system

The autonomic nervous system (ANS) is a critical player in regulating HRV. It consists of two main branches: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The SNS is often referred to as the “fight or flight” system because it prepares the body to respond to stress or danger by increasing heart rate, blood pressure, and energy availability. On the other hand, the PNS is known as the “rest and digest” system, promoting relaxation, recovery, and energy conservation.

The balance between these two branches determines the level of HRV. When the parasympathetic nervous system is dominant, HRV tends to be higher, indicating a state of relaxation and recovery. Conversely, when the sympathetic nervous system takes over, HRV decreases, signaling stress or anxiety. Understanding this balance helps us interpret HRV readings and their implications for our health and well-being.

How is heart rate variability measured?

HRV is an important metric because it can indicate cardiovascular health, reflect balance (or imbalance) in the autonomic nervous system, and aid in the early detection of heart disease, hypertension, and other cardiovascular concerns. Still, how is HRV measured?

Traditionally, HRV has been measured through an electrocardiogram (EKG), a test where electrodes are applied to key areas while the time between heartbeats is measured. For these tests, it’s standard to wear a heart rhythm monitor for any time between 5 minutes and 24 hours.

However, this is not the only way to measure HRV, and it is far from the most convenient. Wrist-worn fitness devices, while accessible and commonly used, especially by athletes, may not provide the same level of data quality as medical devices used in clinical settings.

Shen AI uses remote photoplethysmography (rPPG) to measure HRV with just a 1-minute face scan. No electrodes, and no time commitment. With its non-invasive and convenient ability to track HRV, Shen AI is ideal for those in the healthcare, mental wellness, and fitness industries.

What happends inside Shen AI:

1. Face scan: A smartphone camera “sees” the user’s face, with the video capturing small changes in skin color that correlate with blood flow beneath the surface of the skin.
2. Advanced AI: AI algorithms analyze the signal, detecting color fluctuations that correspond to blood oxygen changes in the vessels.
3. Measuring vital signs: Using the rhythm and intensity of these color changes, Shen AI is able to accurately determine heart rate, blood pressure, respiratory rate, and, of course, HRV, among dozens of other health metrics.

AI health monitoring allows you to have insight-dense data at your disposal, improving care for your patients and clients.

Measuring and interpreting HRV

Accurately measuring HRV involves detecting each heartbeat and the time intervals between them. There are several technologies available for this purpose, including electrocardiogram (ECG) and photoplethysmography (PPG). ECG-based methods are considered the gold standard, as they detect the R wave in the QRS complex and calculate the time between R waves (R-R interval). PPG, on the other hand, measures blood flow changes and calculates the inter-beat interval (IBI).

Each method has its advantages and can provide valuable information about HRV. However, interpreting HRV requires an understanding of normal ranges and patterns, as well as the factors that can influence these readings. By considering these factors, we can make more informed decisions about our health and wellness.

Factors that affect HRV

Several factors can influence HRV, including:

• Age: HRV tends to decrease with age.
• Sex: Females generally have higher HRV than males.
• Fitness Level: Athletes often exhibit higher HRV compared to non-athletes.
• Stress: Chronic stress can lead to a decrease in HRV.
• Sleep: Poor sleep quality can negatively impact HRV.
• Diet: A healthy diet rich in fruits, vegetables, and whole grains supports better HRV.
• Physical Activity: Regular exercise can improve HRV.
• Medical Conditions: Conditions such as heart disease and diabetes can affect HRV.

Understanding these factors can help us take proactive steps to maintain or improve our HRV and overall health.

Applications of HRV

HRV is not just a metric to jot down in your patient’s or client’s health record; it offers significant insight into their health and wellness and can also guide preventative action to ensure they remain healthy. Mental health issues such as anxiety and depression can influence HRV levels, highlighting the importance of monitoring HRV for mental health.

Three key applications of HRV include cardiovascular health, mental health, and physical fitness.

Cardiovascular health

HRV, as a direct measurement of the heart’s variability between beats and its ability to adapt, can offer insights into the health of the heart and the risk of various cardiovascular issues.

One study on HRV found that a higher HRV is associated with a lower lifetime risk of cardiovascular risk. Based on this knowledge, a low HRV can indicate that cardiovascular disease may be more likely to develop at some point. Knowing this, practitioners can then help their patients with low HRV take steps to boost their cardiovascular health and prevent this disease from setting in.

As a bonus, continuing to monitor HRV can show the effectiveness of these interventions—are they making a difference in the patient’s life, or is more attention needed?

Another study found that low HRV predicts an increased risk of cardiovascular events such as atrial fibrillation, stroke, and major adverse cardiac events. Again, practitioners can use HRV to identify when there is a need for intervention.

In case of a medical emergency, it is crucial to contact a physician or emergency services immediately to address any significant health issues.

Mental health and the parasympathetic nervous system

HRV, as a measure of the heart’s adaptability, is often an indicator of how the body handles stress. If someone has a high HRV, they can handle stress well, whereas a low HRV exhibits poor maintenance of stress, which leads to chronically high stress levels.

There are both physical and mental implications of stress. High stress levels, resulting from a high amount of the hormone cortisol, can cause heart and breathing rates to increase. Blood pressure, as well, can be high in those with chronic stress.

These reactions are a part of your fight-or-flight response, designed to help you get out of danger. The sympathetic nervous system triggers this fight or flight mode during perceived danger or anxiety, leading to physiological changes such as increased heart rate and adrenaline release. However, when stress is constant, these effects can wear on the cardiovascular system, forcing the heart to work harder than it can feasibly handle, which is why stress increases the risk of cardiovascular health problems. HRV can indicate whether the body is in a state of stress or relaxation, providing valuable insights into the autonomic nervous system’s activity.

Stress can also impact mental health. Stress can make it hard to remain emotionally resilient, which allows the actions of the day and words said by others to have a greater influence on your emotional well-being. For instance, instead of being able to see that a hurtful remark was said out of jealousy, someone who is stressed may instead take the words to be true, even if, when not under stress, they would know that they’re not.

By monitoring HRV, mental health professionals have a quantitative factor that can provide insight into someone’s mental state. In many cases, mental health is hard to monitor because it relies on the patient conveying their emotions and internal struggles—with HRV, practitioners can know to be on alert for mental health struggles solely based on a number.

Physical fitness and wrist-worn fitness devices

HRV can be a valuable tool for monitoring fitness performance and recovery, allowing athletes to reach their maximum potential without injuring themselves.

For instance, HRV can help athletes and fitness enthusiasts understand their training load and whether their bodies are ready for intense training or need more recovery. HRV data can also help athletes fine-tune their training programs, adjusting the intensity of the training based on HRV trends to boost performance.

Monitoring HRV can also help optimize recovery. Specifically, a higher HRV is often indicative of a well-recovered, adaptable body, while a lower HRV suggests fatigue or stress. By monitoring HRV, athletes can ensure they are getting the right amount of recovery to support their body’s needs. This can help prevent overtraining, which lessens the risk of injury.

Specialized devices are crucial in providing accurate HRV data, which can help athletes optimize their training and recovery. With the help of HRV monitoring, athletes can boost their performance by upping the ante when the body is ready or focusing on recovery when the body needs a break. The body knows what it can handle, and HRV monitoring allows you to listen.

HRV: A tool for the healthcare industry 

HRV is a valuable metric that has applications within many fields, including cardiology, psychology/counseling, and physical training. 

Athletic individuals can use HRV to optimize their training and recovery, boosting their performance and reducing the risk of injury. HRV can also predict an individual’s risk of life-threatening physical conditions, such as cardiovascular disease, and quality of life-reducing conditions, such as chronic stress and anxiety. When practitioners utilize HRV data, healthcare becomes proactive rather than a form of damage control. 

Ultimately, HRV offers insights into the inner workings of our bodies, and Shen AI makes it easier to measure HRV with just a camera and one minute of your time. Learn how Shen AI tracks HRV using AI and provides real-time, non-invasive health insights. Get your 1-minute health check with our demo.