Could the secret to improving your sleep, spotting the early signs of illness and staying slim and happy lie in monitoring your pulse constantly — using just a shop-bought fitness tracker?
That’s the promise being made for an increasingly popular health strategy that focuses on the fact that our pulses can vary from heartbeat to heartbeat by a matter of milliseconds.
This subtle shift in pulse timing is called heart rate variability (HRV). HRV is something that’s long been measured in medical settings with an electrocardiogram — using sensors attached to your chest to check the heart’s electrical activity.
A high (or good) HRV is where your pulse naturally varies between heartbeats when you inhale and exhale — your pulse quickens as you inhale and slows as you exhale.
With a low HRV, there is less variation — the heart beats more steadily, like a clock. This is seen as a sign of stress and, increasingly, potential ill health.
Indeed, HRV is becoming something of a buzz-phrase in the wellbeing world, and HRV-based therapies are now being adopted by complementary therapy centres such as the Body and Mind Clinic, based in London’s swish Kensington and Knightsbridge, and in private clinics such as Nova Recovery in North Ayrshire, Scotland, where it’s being offered to treat alcohol and substance addictions.
Dr Torkil Færø claims that using a wearable fitness tracker to monitor heart rhythm can enable people to turn back their biological clock, live longer and lose weight, among other things
The Body and Mind Clinic, for example, offers a ten-minute test to assess clients’ HRV levels that involves them sitting with their wrists and ankles wired to a machine that records and analyses their pulse.
The clinic’s website says that a low HRV is ‘a proven indicator of early-stage coronary heart disease, diabetes, and high cholesterol’. Conversely, ‘[a] good HRV reading is powerfully associated with healthy longevity, particularly in people who manage internal stress well’.
Depending on a person’s HRV, the clinic says its experts may recommend supplements, exercise, breath training or relaxation to improve HRV and overall health.
Nova Recovery private clinic’s website, meanwhile, says that its clinicians can analyse patients’ HRV to find subconscious yet powerful triggers that may cause someone recovering from addictions to relapse.
The clinic says that by monitoring their HRV, patients can see how their heart rates respond to hidden stress triggers — this can help them review how they respond emotionally and then modify their behaviours so that the stressors don’t overwhelm them.
But does HRV really matter? Or is there sound scientific research to underpin the claims being made for something as simple as constantly monitoring your pulse?
And on the other hand, could constantly monitoring your pulse actually lead to unnecessary anxiety? Many of the answers may be found in a new book, The Pulse Cure, by Dr Torkil Færø, a GP and emergency doctor who lives in Oslo in Norway.
The 53-year-old’s book has been a ‘runaway Scandinavian bestseller’, having occupied the Norwegian bestsellers’ list for 39 weeks, according to its publisher.
In the book, Dr Færø claims that using a wearable fitness tracker to monitor heart rhythm can enable people to ‘turn back their biological clock, live longer, lose weight, fight illness, be generally healthier, have more energy and less stress, boost their willpower, and exercise and eat optimally’. It is a lot to promise, particularly for a phenomenon that was first discovered as long ago as 1733, when a pioneering Cambridge University scientist, Reverend Stephen Hales, noted that pulse varies with respiration.
Proponents of HRV-based therapies say the key is that your pulse enables you to monitor your autonomic nervous system.
This is a biological mechanism that regulates our bodies’ basic functions without our being consciously aware of it.
This includes our stress levels, alertness, sleep patterns, digestion, inflammation levels, immune system, energy balance and blood-sugar levels. It also regulates our heart rate and breathing rate.
Dr Færø calls this system ‘the body’s hidden drivetrain’ (a term used in the automative industry to refer to all the components that get a car — but in this case, the human body — running).
Scientists have long known that the autonomic nervous system has two modes. The first, the parasympathetic nervous system, is a state of rest and relaxation. The second, the sympathetic nervous system, is a state of stress and activity.
When you are in the parasympathetic state, the distance between your heart beats (i.e. your pulse) varies during inhalation or exhalation. Your pulse quickens when you inhale, to exploit the fact that your lungs are filled with oxygen. Then it slows down when you exhale, to save energy.
This process creates a minute variation in the distance between heart beats — i.e. heart rate variability. This variation is measured in milliseconds and is increased by the parasympathetic state.
By contrast, in the sympathetic state, when you are stressed, your body is rushed and you breathe faster. Your lungs draw in less oxygen and your body can’t afford to slow during exhalation.
He recommends a primarily plant-based diet of fresh whole foods, and avoiding such stressors as a lack of sleep, eating late in the evening, exercising too strenuously of drinking alcohol
As a result, there will be less variation in the distance between heartbeats. Thus, when you’re stressed, your HRV is low.
‘The low-HRV sympathetic state increases heart rate, slows digestion and increases alertness,’ writes Dr Færø. ‘It releases glucose to prepare us for fight or flight. Maintenance work in the body is put on hold and our immune defences are lowered.’
He warns: ‘If we are constantly in this mode, we become exhausted. The body, brain and immune system fall prey to inflammation that creates fertile ground for chronic and fatal diseases.’
Chronic inflammation is widely considered a significant risk factor for disease such as cancer, not least because it over-activates the immune system into a state where it damages the body’s cells.
Indeed, according to immunologist Dr Jenna Macciochi, an honorary senior lecturer at the University of Sussex, ‘HRV is an excellent estimator of your overall immune health. This is because HRV is very sensitive to inflammatory pathways.’
We also know from numerous studies that HRV naturally becomes lower as we age.
A 25-year-old male’s normal heart rate variability might be 50-100 milliseconds (though this variation wouldn’t show in his pulse, measured in beats per minute).
Once into middle age and beyond, the number could drop to a range of 35-60 milliseconds, though the reasons for this are yet to be fully established.
(And note: Dr Færø explains that heart rate variability is unique to each individual — with about 30 per cent of the differences in it genetically determined — ‘this is why it is important not to compare the numbers you get with those of others’.)
Dr Færø’s book claims that by using a fitness-tracker to monitor your HRV continuously, you can learn to modify your lifestyle to optimise your restful, high-HRV states so that your body rests and recuperates healthily.
Furthermore, he claims, a properly recuperated body will then be fully energised to use its low-HRV states to mobilise for healthy daily exercise and work.
Thus, ‘we can balance between time spent being in the stress and resting modes,’ says Dr Færø, who warns that ‘an imbalance between these two will result in physical and psychological issues’.
As for ways to maximise restful high HRV, Dr Færø recommends getting ample sleep, taking naps, meditating and spending time on calming activities. We should also practise breathing exercises. ‘Breathing slowly can “trick” the nervous system into interpreting our environment as calm, thereby activating the high-HRV parasympathetic system,’ he says.
We should also eat a primarily plant-based diet of fresh whole foods — and avoid the main drivers that cause stressful low-HRV, and deplete our bodies’ resources, including: Lack of sleep, eating meals late in the evening, exercising too strenuously, drinking alcohol, being overweight, smoking and suffering emotional stresses such as relationship problems.
If this health advice sounds very familiar — it is: it’s the standard kind of advice you’d read in any health book or NHS leaflet.
The difference is the focus on using your pulse to monitor the effects of lifestyle and to tailor it to improve your HRV, and ultimately health, using a wearable fitness tracker — in other words acting as your own health coach.
High-HRV states charge our bodies’ batteries, and low HRV-states drain them, Dr Færø claims, adding that: ‘Until recently it was hard to know whether your battery is high or low. Now, you can see this on heart rate monitors on a smartphone app.’
You may well have such a device already: certainly the market for heartbeat-measuring wearable fitness trackers is booming — 440million are predicted to be sold worldwide next year, according to the market analyst Deloitte. (Dr Færø recommends that while many of these can do the job, he uses Garmin trackers that have a feature called the Body Battery, which claims to record the levels of physical and mental energy that you have at any time. Garmin’s Body Battery concept was developed not by medical doctors but by Firstbeat analytics, a Finnish technology company owned by Garmin.)
Dr Færø says that, using his regime, he adjusted his eating and fitness to lose 20kg in weight
It’s not an idea with firm medical backing, and Dr Færø warns that you should ‘be prepared: initially your doctor may become annoyed and look down his nose’.
Still, he claims, by following an HRV-optimising programme he managed to adjust his eating and fitness regimens so that he lost 20kg in weight. He did this primarily by stopping eating breakfast and instead fasting until lunchtime, to give his digestive system a long daily rest from 7pm until noon the next day, and also to reduce his calorie intake.
He also recruited 198 volunteers in March 2022 to follow their own HRV-led regimen, and reports that many of them say their lives are now significantly healthier and happier, thanks to monitoring their HRV and ‘body battery’ levels, and adjusting their lifestyles accordingly.
Dr Færø’s study was not, however, scientifically validated independently. Nor was it completely unbiased — because the volunteers were given a 20 per cent discount when they bought their Garmin devices to join the study.
The gold standard for medical studies is randomised controlled trials (RCTs), where a treatment is compared with a placebo, without participants or the medics involved knowing who got what.
But Dr Færø told Good Health that while RCTs tend to produce results that are averaged over large populations, ‘what seems more important than an average found in RCTs are the individual positive results that people report from using the devices’.
He adds: ‘After all, we are anecdotes more than we are averages.’
Dr Færø acknowledges that lowering HRV may not in itself do anything to improve health. (It may instead only be a useful indicator of how we might adopt healthier habits.)
‘We do not have a full picture of the relationships between HRV and health yet,’ says Dr Færø.
‘Does a low HRV cause the onset of the disease, or does the disease manifest itself in a low HRV? The answer is most likely an interaction between the two,’ he says.
Mainstream UK experts are not yet convinced.
Dr Malcolm Finlay, a consultant cardiologist and electrophysiologist at the Barts Heart Centre in London told Good Health: ‘HRV may be a good metric for measuring how stressed or relaxed you are. But in frontline clinical world it has little use.’
One reason, he says, is that HRV monitoring offers only generalised pictures. ‘It’s been shown to be a good overall indicator of stress or relaxation levels across sizeable groups of people, but in individuals it does not always correlate reliably with people’s real stress or relaxation,’ says Dr Finlay.
In other words, you might have a low HRV but not actually be stressed at all.
As for the possible curative powers of lowering one’s HRV, Dr Finlay is sceptical.
‘The cart can easily be put before the horse here. It is more that improvements in your health change your HRV, rather than improving your HRV can directly improve your health.’
Dr Manish Saxena, a cardiovascular specialist and deputy director for research for Barts Health NHS Trust, has conducted numerous studies on devices that measure heart rate variability.
‘You have to make a distinction between lifestyle devices such as watches, and fully validated devices that you find in medical clinics,’ he says.
‘You can assume medical-levels of accuracy only with the fully validated ones, which carry approval marks from the UK Medicines and Healthcare products Regulatory Agency, the European Medicines Agency or the US Food and Drug Administration.
‘Devices that don’t carry these approval marks must be considered “lifestyle” ones which cannot be considered medically accurate,’ argues Dr Saxena.
Indeed a spokeswoman for Garmin Europe told Good Health that while there have been more than 700 scientific studies performed on their health gadgets’ features, ‘Garmin watches are not approved medical devices and are not designed to diagnose or treat any disease or condition’.
Amitava Banerjee, a professor in clinical data science at University College London, takes a robust view: ‘Wearable monitors are basically pseudoscience,’ he told Good Health.
‘You won’t find reputably published scientific papers backing their validity and accuracy as medical devices.’
Measuring HRV might have some diagnostic use with seriously ill patients but not as a lifestyle aid, says Professor Banerjee.
‘In populations with heart disease, having low HRV is linked with a higher mortality rate over time,’ he explains.
‘But there is no convincing evidence from studies of large numbers of people that monitoring HRV will result in their doing anything about it or improving their long-term health.’
He adds: ‘The idea of a “body battery” is a confection. It’s not medical science.’
Furthermore, Professor Banerjee is concerned that such self-monitoring may have unintended consequences. ‘The premise that “the more monitored I am, the healthier I am”, is wrong,’ he says.
‘What can result instead is the creation of populations of anxious well people who may unnecessarily seek private or public health treatments for problems they don’t have,’ Professor Banerjee argues.
Nevertheless, he does think that Dr Færø’s suggestions for improving people’s HRV are positive in themselves.
‘I can say that at least they are not doing any harm in the things they recommend you do, which are fairly commonsense,’ he says.
This view is supported by Dr Paul Marsden, a psychology lecturer at the University of the Arts London, who has researched the psychological and physical effects of activity trackers.
‘Gadgets are good for encouraging healthy behaviour change because they enable you to set goals and then track your progress towards them — which are the most effective known ways to nudge people towards change,’ he says.
‘My work on trackers shows that they give people a useful sense of control over their health, which in itself improves mental wellbeing.
‘Once you start tracking and setting goals, the technology can encourage you to do things such as exercise more, improve your sleep, drink less [alcohol] and do breathing exercises.’
And even though HRV’s clinical validity may be arguable, Dr Marsden says, ‘in an increasingly science-oriented society, HRV will catch people’s enthusiasm and give them something to focus on.
‘Whether HRV is a real factor or is just a placebo — at the end of the day that really doesn’t matter if it helps people to improve their health.’
The Pulse Cure, by Dr Torkil Færø, is published by Quercus at £16.99.