Heart Rate Variability (HRV) and Heart Rate (HR) Tracking

What is the key difference between HRV and HR? How and when should we track and improve heart rate variability?

Recent developments in digital health have introduced various wearable devices and apps for acquiring vital biomarkers and obtaining advanced health metrics, ultimately transforming the way we measure data and use it to understand and improve our health. A metric that has recently received a lot of attention is called Heart Rate Variability (HRV), and owes its popularity to the ability to provide valuable, non-invasive insights into our health status and expand the potential of digital biofeedback.

Although often measured alongside the Heart Rate (HR), HRV is a metric that offers more detailed and accurate information than HR alone. To understand how these two vital measurements can be fully and unambiguously interpreted, this article will explain the similarities and differences between HR and HRV, as well as how they can be applied to health tracking and improvement.

What is Heart Rate and how to use it

Measuring HR means obtaining an average beat-per-minute (BPM) value, which tells us how fast the heart is beating. Easy to record and interpret, HR has perhaps been the most widely used metric in medicine for centuries. Most people show an average HR value of somewhere between 60 and 100 BPM in a rested state. Different HR readings can offer insights into the state of our cardiovascular system.

A low HR reading shows measures of < 60 BPM and usually indicates that the body is in a rest-and-digest state. Low HR is also normal in athletes or during sleep. It can also be a sign of a condition called “bradycardia”, which causes fatigue, dizziness etc. A higher HR reading shows measures of >100 BPM and usually means that the body is under physical or psychological strain. High HR is normal in some cases, like during exercise, or it can indicate a condition called “tachycardia”, which is associated with various symptoms and complications.

However, the heart rate is, per definition, a measurement that provides an average value and only shows how many times the heart beats in a minute. An average of 60 BPM could mean that the heart beats once every second, or that it alternates at a 0.6 seconds followed by a 1.4 seconds rate, or at any of the endless range of time intervals between successive beats. In summary, the heart does not beat to a regular pattern, but rather slows or fastens its pace to adapt to several physiological or pathological factors. HR measurements at any given time, therefore, provide limited information about human health or well-being. 

What is HRV and how to use it

HRV represents the variability in the time intervals between successive heart beats. In contrast to the HR, the HRV takes into account what happens in each heartbeat. Such variability in the heart activity has its origins in the Autonomic Nervous System (ANS), which comprises two branches and regulates various automatic processes in the body, including digestion, heart rate, breathing, even sexual arousal. . Given its strong connection with the activity of the ANS, measuring HRV has a wide range of applicability. 

By helping us understand the current state of the autonomic nervous system and how well it is functioning, HRV provides insights into all the processes in the body that are equally controlled by ANS. This means that tracking HRV can help us understand the link between cardiovascular activity and the respiratory system, stress management, fitness and recovery, and other health related processes and functions inside the body.

A high HRV at rest usually indicates that the heart is operating well, and that it adapts to various stressors quickly and efficiently. On the other hand, a low HRV at rest can be an indicator of too much stress, a previous intense workout, or several other impaired processes in the body.

HRV therefore represents a metric that is more insightful, widely applicable, and valuable than simple HR recordings. However, quantifying the variability between successive heartbeats requires the calculation of complex scores from the HRV readings and more sophisticated tools for interpretation than simple HR readings.

Vital biomarkers collecting and interpreting

Recent advancements in technology have enabled smartphone apps and wearable devices to collect and interpret HRV metrics in a non-invasive, affordable, and convenient way. This makes HRV readings within everyone’s reach, easy to interpret and implement in your health management habits. HRV and HR have commonly been associated and are even mistakenly considered equivalents. Understanding the difference between HR and HRV and how they can be used is very important, as it can help you reach health related goals and establish better habits more efficiently.

When to measure HR

The best moment to measure HR at rest is in the morning, ideally in bed, after a good night’s sleep and before the first coffee. HR at rest provides basic insight into how well your heart is functioning, whether you exercised enough etc. Once you know your average HR at rest, it is indicative to track it during strenuous conditions (like during exercise), as it reveals how physical exertion affects your heart rate in real time. This type of tracking is a useful basic tool for training your heart and adjusting your routine to match the state of your cardiovascular system.

When to measure HRV

Interpreting HRV metrics offers insights into the way the ANS is functioning, which can help you understand the state of your overall health, as well as your body’s ability to manage stress and recover from physical exertion. However, that also means that HRV is a very sensitive metric and, therefore, some additional planning and interpretation are required when it comes to its measurement, especially when performed in short intervals.

While valid HR can be measured during an activity, HRV is more easily interpreted before and after a certain task or challenge, in more “controlled” conditions (e.g. without interference). For measuring the effect of meditation on stress recovery, it makes sense to compare HRV before and after that activity in absence of additional stressors or relaxants. 

The most important thing to keep in mind is that although HRV and HR are commonly considered to provide similar vital data, they are in fact very different from one another and should be measured individually. HR is a valuable tool for basic medicine and for interpreting the immediate effect of physical and psychological exertion, while HRV offers deeper insights into the functioning of the ANS and all the biological processes it regulates.

If you are interested in knowing more about HRV and uncovering the full potential it has for helping the body learn how to better manage stress, improve fitness, and even help improve mental health, visit our full collection of HRV related articles.

Read more about HRV and HR:

What is HRV and how can it leverage digital health?

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