Management theorist Peter Drucker is credited with the saying, ‘What gets measured gets improved.’ Which as anyone who wears a smartwatch knows is a falsehood of seismic proportions. Wading through the torrent of information and apps proclaiming to guide you to a new, healthier and happier existence would result in muscle strain (which there is almost certainly a preventative app for). Data is king, but only if that data can be easily interpreted and applied to your cycling and daily life.
Which brings us to HRV or heart rate variability. Glance down at your wrist and, chances are, that life-controlling screen reflects your HRV score. It’s on Garmin, Apple Watch, Polar, Coros, Whoop… It tells you if you’re up, down or possibly middling. But what do the numbers mean? And how can you make them more than a number without losing yourself in a labyrinth of algorithms?
Most importantly, how can the numbers benefit your training? First, let’s start by explaining exactly what HRV is.
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An insight into your nervous system
‘Heart rate variability refers to the variations in time intervals between successive heartbeats,’ says Paul Laursen, acclaimed physiologist, sports scientist and brains behind training software Athletica. These variations between beats sit anywhere between 0.7 and 1.2 seconds.
‘Our heart rate fluctuates almost randomly. However, this randomness provides insights into our body’s response to various life stressors. Not just training load but psychological and emotional stress, and even nutrition and sleep quality,’ he adds.
Think of HRV as a window into your body’s autonomic nervous system, Laursen suggests. This regulates essential functions such as heart rate, digestion and your response to stress.
‘In short, by analysing heart rate variability, athletes can gain a deeper understanding of their physiological state, enabling them to adjust their training approach accordingly,’ he says.
Unlike for heart rate or blood pressure measurement, there’s no determined ideal HRV score. One rider’s normal range could be low in the 50 RMMSD range, while another’s baseline could be in the 100s. (RMSSD is the ‘root mean square of successive differences’ and is a standard statistical measure of HRV. It’s considered the most accurate measure of autonomic nervous system activity.) That said, while HRV values vary per person and by day and circumstance, higher HRV is considered a better health indicator than lower HRV.
The idea is that if your HRV is in fine fettle, carry on as planned and tame that 100km threshold ride packed with 10% climbs; if it’s low, stay at home and watch Loose Women. It’s this customisation that, in theory, helps you to optimise training and reach your peak. And it’s supported by science.
Take a 2020 study in the Journal Of Strength And Conditioning Research by a group of scientists including Dr Dan Plews, once colleague of Laursen, who compared the effects of a training plan directed by HRV versus block periodisation (BP) in well-trained cyclists over an eight-week period (block periodisation segments training into distinct blocks or cycles, each focussing on a specific fitness component or goal, allowing for highly concentrated workloads. It’s particularly beneficial for high-performance athletes seeking to achieve peak performance at specific times throughout the season).
Twenty cyclists were divided into two groups: one followed HRV-guided training, while the other adhered to the block approach. The results? The HRV-guided group significantly improved their maximal oxygen uptake, peak power output and performance over a 40-minute time-trial. The BP group also improved but to a lesser extent. A further 2021 review of HRV literature concluded that ‘HRV monitoring can be beneficial for optimising endurance training adaptations’.
Commercial accuracy
So, evidence from the tight confines of a laboratory suggests HRV could have an important role to play in maximising each and every pedal stroke. But what about in the dynamic, uncontrolled real world? How useful and accurate are commercial wearables when it comes to HRV?
To answer that, we turn to Marco Altini. The Italian founded HRV4Training, an app that is regarded as the commercial gold standard. You place your finger against your smartphone’s camera and the app does the rest. He’s worked with many technology companies to integrate HRV into their products, including a collaboration with Laursen at Athletica. He’s a data science advisor at Oura (the health-tracking ring that you wear on your finger), has a PhD in data science and two masters. In short, Altini knows HRV and his data feedback is trusted.
‘A few of the wearables that are on the market today can provide reasonably accurate HRV data when collected in the absence of movement, for example during the night,’ he says. ‘In my experience this is the case for Oura, Whoop, Garmin and Coros. There are also studies looking at spot checks with Oura and HRV4Training, the app I developed, both using the fingertip and phone camera and paired to a chest strap. The studies show both systems are accurate – and more accurate than other apps or wearables.’
Broadly, your options are phone and app, smartwatch, wristband or ring. Accuracy seems solid enough across all with choice down to personal preference (for this author, it’s a ring because I’m a dodgy sleeper, so wish not to be weighed down by sleep-hampering watches or wristbands).
For Altini, it’s more about interpretation than the HRV monitor itself.
‘Make sure not to confuse HRV with the made-up scores wearables provide you,’ he says. ‘HRV is your actual physiological response. That’s why it’s much more informative about the state of your body than any attempt to capture your “recovery” or “readiness”.’
Trend spotting
That’s key. In an effort to interpret this information in convenient, instant and catchy soundbites, wearable companies can be guilty of creating confusion rather than clarity. It might seem the perfect performance solution to wake up, look down at your wrist and be told whether you’re ready to bury yourself in hill reps or you need to go for a recovery sojourn on the turbo, but that’s fraught with misinformation and is too simplistic.
Instead, maximising HRV’s usefulness requires tracking trends over time. Riders can then identify patterns and deviations from their baseline, allowing for more nuanced adjustments in training instead of knee-jerk reactions.
‘Never look at a single individual value. That’s missing the show,’ says Laursen. ‘You need to look at the bigger picture. That’s why, as an example, with our system we import overnight HRV values from a Garmin device or Strava and highlight a normal value based on the 60-day average. This is represented by an orange line. On the same graph we feature your most recent seven-day average – a blue line. We’ll only make noise when your seven-day average runs higher or lower than normal.'
So, accumulating sufficient HRV readings to forge your own HRV range will help you spot trends. And that’s key because HRV is incredibly sensitive to change.
‘Even swallowing your saliva or drinking water will impact your HRV, even though it’s not a stress response,’ says Altini. ‘It’s because cardiac activity changes in response to even basic activities like those, which we can capture with an HRV measurement.’
It’s why standardising when you take your daily HRV readings each day is essential to see through the HRV fog. And the best time is when you wake.
‘Morning measurements allow us to measure our resting physiology as far as possible from the previous day’s stressors and after the restorative effect of sleep, and as such I consider them the ideal way to capture our stress response,’ says Altini.
‘A late dinner or late exercise results in increased heart rate for several hours during sleep, which is no problem, but would be captured as a negative response by wearables measuring in the night.
‘Also, morning measurements allow us to measure in a body position other than lying down, which is key. Measuring HRV while sitting or standing exploits the orthostatic stressor [meaning that by changing body position, you trigger a physiological response and the body has to re-normalise]. Especially for endurance athletes with low resting heart rates, measuring while sitting [or standing] is a good idea. At times, the body needs to be challenged slightly for us to better understand its response and this isn’t the case during sleep.’
Professional perspective
Who you sleep with also has an impact on HRV. Peter Leo is coach at Jayco-AlUla and head sport scientist at Australian Cycling and has seen HRV readings fluctuate wildly at three-week Grand Tours.
‘In a perfect world, each of the riders would have their own rooms at races like the Tour de France,’ he says. Tour organiser ASO sorts the riders’ hotels, and because of budgetary and availability reasons, that means coupling up.
‘We’ve noticed ourselves, and there are good studies out there showing similar, that HRV drops and sleep quality is not the same when sleeping in the same room as someone else.’
We’ll leave you to broach the subject of separate rooms to your partner, all in the name of completing the Fred Whitton ten minutes quicker. The point is that HRV is impacted by so many variables that even the professionals must devote time to tracking HRV data for any meaningful conclusions. And they are people who ostensibly just ride, eat and sleep. You ride, work, clean, eat, parent, socialise and sleep. In many ways the lives of amateurs are more complex than professionals, with alcohol in particular being an HRV batterer. But there are conclusions to be made with HRV, as long as you commit and rack up the data. Take Leo’s personal experience.
‘For me, it has been an up-and-down, busy year with a packed WorldTour calendar plus the Olympics,’ he says. ‘I’m certainly more attuned to my body with the data from the Oura ring I use and can see that I’m very sensitive around travel. That’s why it’s ideal that I arrive at an event a day earlier to bag additional pre-event sleep, or when travelling home take a half day or day off work to recharge. I’m then more impactful with my work. It doesn’t always happen but that’s the ideal.
‘We care a lot about athlete wellbeing but all of us in this cycling ecosystem – coaches, soigneurs, mechanics, DSes – undertake a high workload and it would be beneficial to monitor their HRV, examine resting physiology and ensure sufficient recovery time is pencilled in.’
Leo won’t be the only one whose HRV readings skew when travelling, so take note if your 2025 goal sportive is an international event such as L’Étape du Tour or Maratona dles Dolomites. And that applies to right up to the event.
‘One of its key uses on the team is tapering into competition,’ Leo says. ‘I tend to use HRV in conjunction with heart rate for an even clearer picture of what’s going on [as you might with power and heart rate] and we often see that around three or four days before a race, a rider’s HRV drops from their baseline despite their resting heart rate remaining the same.
‘That could make some riders panic, but it doesn’t once we’ve explained. You see, it’s a bit of a paradox because when riders freshen up during a taper, they’d expect their HRV values to rise. In fact it’s often the opposite. Their parasympathetic system, represented by HRV, is somewhat confused because the rider never normally feels so rested. They’re adapting and ready to race. It would be different if their resting heart rate rose too – a 5bpm increase in resting heart rate is a sign of illness – because then it’s more about an immune response than adaptation.’
The future equals clarity
It’s clear that HRV has its uses. But that’s the only thing that’s clear when it comes to HRV. As Laursen says, it takes commitment to optimise the results but it is worth it. Collect the data, create your ranges, spot trends and maximise your riding.
‘HRV highlights your capacity to adapt,’ he says. ‘If your figures are low over a set period, simply beasting yourself will harm your immunity as you’re not in a state to adapt. Good, consistent, higher figures, on the other hand, mean you can train consistently and progressively.’
Which will be effortless if Laursen’s baby Athletica has its way. The coaching and training platform utilises artificial intelligence. This, he says, not only helps to smooth out HRV data, but will make understanding the myriad metrics at a cyclist’s disposal much easier.
‘I guess it will be like an enhanced TrainingPeaks, but that’s only my opinion, of course,’ he says. ‘You’ll have a dashboard that features data such as power, heart rate and HRV, so you’ll easily see trends across the board and how they impact each other. It will be like having an assistant coach in your pocket.’
HRV has been simmering for years, because while the experts have seen its merits, trying to unpick the data for meaningful interventions is the fast-track to madness. But that’s changing and potentially set to change apace with machine learning. The future of HRV could soon be clarity over confusion.
Capture your heart
Tech options for measuring heart rate variability
Watch: Garmin Fenix
From £429.99 | garmin.com
Watches such as the Garmin Fenix use a PPG optical sensor, which emits pulses of green light into tissue then measures how much is reflected back by red blood cells. Considered pretty accurate, if slightly hampered by anything that impedes the consistent passage of light through skin.
• Read our Garmin Fenix 6 Pro Solar review
Ring: Oura Ring 4
From £249 | ouraring.com
Favoured by many athletes for being the least obtrusive option, the Oura Ring uses PPG technology similar to most wearables so is prone to the same impediments to accuracy – movement, sweat etc – albeit the position on a finger is a relatively dry and stable one.
Chest strap: Polar H10
£86.50 | polar.com
Arguably the most accurate way to measure HRV, chest straps measure the electrical signal emitted by the heart to determine beats and HRV. Given the elasticated mounting, position and the fact salty sweat is a good electrical conductor, chest straps remain very accurate.
• Read our Polar H10 Heart Rate Monitor review
Phone app: HRV4Training
£9.99 | App Store and Google Play
This app cleverly turns a phone camera into a surrogate PPG sensor, with the flash emitting the light pulses and the camera sensor doing the measuring. From there, HRV4Training provides all manner of metrics and extrapolated data to help you train and recover.
