What Is HRV? How to Use It to Understand Your Recovery

HRV or Heart Rate Variability has made its way into public consciousness thanks largely to the increase of personal health tracking devices like smart watches and other wearable devices.

So much so that some of the most popular wearables on the market now provide HRV data right alongside your sleep data and recovery metrics. For those of us invested in tracking their health metrics on a daily basis, you probably have a vague sense of what HRV actually means and an even vaguer sense of what you should be doing with it. 

To combat this uncertainty, we’ve put together this simple guide that breaks down what HRV actually measures, how it works, why it matters, and how you can use it to better understand your body and make smarter decisions about training, recovery, and lifestyle.

In simple terms, heart rate variability (HRV) refers to the slight irregularity or fluctuations in times between heartbeats. 

Heart rate variability fluctuations are measured in milliseconds and not something that most of us think about on a daily basis – unless presented with the data from a wearable device. 

Contrary to the metronome analogy that is sometimes used to describe a heartbeat, your heart doesn’t actually beat like a perfect metronome. Even when resting, the gap between your heartbeats (variation) will vary slightly – maybe 0.88 seconds, then 0.94 seconds, then 0.89 seconds. Those tiny changes are your heart rate variability.

When those gaps vary more – a high HRV – it usually means that your nervous system is relaxed and your body is in recovery mode, handling whatever life throws at it without strain. A high HRV means that your body is well rested, relaxed, and ready to handle what comes next. Whether that’s a challenging workout in the gym or stressful day at work – a high HRV means your body is ready for those challenges.  

When those gaps between vary less – a low HRV – it means that your body is under a higher level of stress or alert. Low heart rate variations means that your body is dealing with stress, and you are burning energy to handle that stress. A low HRV is something that generally crops up when we’re run down, stressed at work, getting sick, or training too hard. 

If that explanation was a bit complicated – here’s what you really need to know:

• High HRV = your body is relaxed and recovering well.
• Low HRV = your body is stressed or working hard.

For the average adult, the average normal heart rate variability is ~42 milliseconds. Anywhere between 19 and 75 milliseconds is in the healthy range. Athletes and those who maintain very high fitness will often have an HRV score of 80+. However, there is no ‘normal’ score, heart rate variability will depend on your age, genetics, health history, and heart rate trends.

Low heart rate variability can be caused by a number of lifestyle factors, health conditions, or physical or mental stressors. Maybe you’ve slept for eight hours, but still feel exhausted.  Or you’ve been travelling, eating differently, and not recovering as well as normal. Some are easy to address, whilst others may require a more considered approach to overcome.

Overtraining – pushing too hard too soon can mean that your body does not properly recover or adapt. Stress without adaptation is indicative of overtraining and can cause a low HRV.

Mental stress – mental stress including pressures in your work, home, or social life can keep your nervous system in a perpetual state of fight or flight and cause a low HRV.

Poor sleep – Insufficient or irregular sleep patterns are one of the most common causes of low HRV.  

Alcohol consumption – Alcohol consumption is a common driver behind changes to HRV. Metabolising alcohol places stress on the body’s central nervous system. Even in moderation, alcohol consumption can notably impact HRV.

Illness – Temporary and chronic illness impacts the central nervous system and causes fluctuations to HRV. In lieu of physical symptoms of sickness, HRV can be a useful way of detecting sickness.

Dehydration – Temporary dehydration makes your body work harder to relax and recover. Changes to HRV could be as simple as being dehydrated after a workout or simply not drinking enough water throughout the day.

Poor nutrition – Poor diet and nutrition is a common underlying factor behind a low HRV. Skipping meals, consuming processed foods, or missing essential micronutrients can all impact your body’s ability to recover and regulate the autonomic nervous system.

A 2023 study published in the International Journal of Environmental Research and Public Health examining HRV measurement in smart wearable devices tested most major brands/devices in the wearable space and concluded that these devices were – by and large – reliable enough to track trends but still exhibited inconsistencies across devices.

In simple terms, wearable devices provide a good gauge and are a fairly accurate way to track and measure changes even if they don’t quite match the accuracy of ECG-based HRV monitoring.

The biggest issue with accuracy comes down to the way these devices record. Some popular wearables capture HRV data in one-minute windows which is considered extremely short. The difficulty with this data is that temporary external factors like stress, caffeine consumption, and hydration could all have a meaningful impact on HRV data. In isolation, it can be difficult to make sense of these readings. 

The takeaway is that HRV data is more useful and accurate when recorded as an average, and you can look at HRV trends, rather than an individual reading. Looking at a weekly average of consecutive similar days rather than relying on outliers or random snapshots will naturally improve the value (and importance) of HRV data.

HRV data can provide a meaningful insight into how you are resting and recovering between workouts, after sickness, or simply handling every day stress. With enough data, HRV insights can help to inform how well you are recovering and whether your body is recovering properly. 

It’s important to understand that HRV data in isolation doesn’t mean a whole lot – one weird HRV reading does not mean a whole lot. Measuring and tracking HRV over time helps to establish a baseline that can be used to gauge fluctuations and inform decisions around rest and recovery.

Many of our guests arrive feeling what we call “wired, but tired”; their bodies are running on adrenaline, stress, and are on the precipice of burnout. HRV can often help to explain exactly what’s happening beyond the surface. 

We think about HRV as another clue as to what’s going on in your body, not necessarily as a metric to chase or “optimise”. It’s not necessarily about grading your score, it’s more about understanding what may be contributing to feeling restless, exhausted, or disconnected. We think of HRV as one piece of the puzzle, rather than the whole picture. 

Over the week at Mana, we find that many guests do see an improvement in HRV. Not because we’re specifically focusing on it, but because guests are getting deep restorative rest, are managing stress, practicing and learning how to integrate breathwork, and reconnecting with their bodies. 

We use HRV and a number of other baseline metrics to understand sleep, stress, and recovery within our retreats, including the Longevity & Lifespan retreat, and the Deep Rest sleep retreat at Mana.

• Heart Rate Variability Measurement through a Smart Wearable Device: Another Breakthrough for Personal Health Monitoring?