The latest devices don’t just count your steps, they can even identify a faulty heartbeat or risky sleep disorder — and tell you when to stop drinking coffee
Every year there seems to be a new advance in the technology we can use to track our own health. Most recently, the latest Apple Watch apparently alerts wearers to their risk of sleep apnoea (where breathing is temporarily interrupted during sleep).
Meanwhile, a number of health and fitness ‘wearables’ detect heart rate and other health metrics from sleep patterns to blood oxygen levels, alongside more familiar functions such as tracking steps and other activity levels.
They are now so hi-tech that some arguably hover on the brink of being medical devices (though experts are keen to stress that while these gadgets are all fairly accurate and constantly improving, they are no match for the sophistication of supervised medical tests).
I tried seven of the leading fitness trackers and rated them based on my experience and on expert Dr Kingsnorth’s comments, says Libby Galvin
How they work varies. With regards to sleep, the devices rely on sensors – for example, an accelerometer and gyroscope that detect movement, plus sensors for heart rate and blood oxygen levels, to detect interruptions in breathing patterns, says Dr Andrew Kingsnorth, a lecturer in digital health technologies at Loughborough University.
Apple is the first to link these breathing disturbances specifically to sleep apnoea warnings. ‘A person is prompted about possible sleep apnoea when they experience consistently elevated breathing disturbances during a 30-day window,’ says Kingsnorth. However, he adds, the ‘watch is more likely to detect severe cases than mild ones’.
For heart rate, fitness trackers use an optical technique (known as photoplethysmography) says Dr James Sanders, a senior research associate in digital health for lifestyle medicine, also at Loughborough University.
‘The device emits green light into the skin and measures the amount of light reflected back.
‘Blood absorbs light differently depending on its volume, which varies with each heartbeat. By analysing these variations, the smartwatch calculates the user’s heart rate.’
They can also calculate your heart rate variability (HRV – the time between each heartbeat). A higher HRV is usually healthier.
But the accuracy of these measurements may be affected by several factors including body movement, circulation and ‘even body cream’, adds Dr Sanders.
Many trackers also work like a pulse oximeter, measuring blood oxygen saturation levels.
The device shines red and infrared light into the skin, which passes through the blood vessels. Oxygenated blood absorbs more infrared light and reflects more red light, Dr Sanders explains, while deoxygenated blood absorbs more red light and reflects more infrared light.
The watch’s algorithms calculate blood oxygen levels by measuring the ratio of reflected light.
This is ‘particularly useful for monitoring respiratory health’, adds Dr Sanders, but warns that their accuracy can be undermined by movement, even ‘skin pigmentation [studies show accuracy is poorer on darker skin] and ambient light’.
You can only use an Apple watch if you also use an iPhone, and half of UK mobile phone users use a different smartphone. Fortunately, there is a multitude of fitness trackers, smart watches and wellness rings available that can be used with any phone.
As well as measuring various health metrics, these devices promise to track your exercise efforts in everything from Pilates to powerlifting.
I tried seven of the leading fitness trackers and rated them based on my experience and on Dr Kingsnorth’s comments. (A note on accuracy – I wore many of these trackers in combination and they delivered similar results, for example, for sleep duration, heart rate and steps.)
Whoop 4.0
From £229, whoop.com
Features: Tracks steps, sleep stages, sleep ‘need’, heart rate, HRV, post-exercise recovery, stress, blood oxygen, skin temperature and more.
My verdict: Worn as a fabric wristband – the gadget is a little black plastic rectangle – you view the data this collects on your phone via a linked app.
I found its sleep insights useful – graphs of ‘sleep consistency’ record the time you fall asleep and wake each day. Consistent sleep patterns are good for you, so this gave me something to aim for.
It also assessed sleep ‘need’, suggesting how many hours you should aim for per night based on your previous night’s sleep and health measurements that day. But rather than paying for the device itself, you pay a monthly or annual subscription to use it and the accompanying app – and, long term, it is costly.
Expert verdict: ‘This tracker can provide you with analyses about your health including strain, recovery, stress and sleep need, which is standard for most fitness devices,’ says Dr Kingsnorth.
‘However, the fact that it doesn’t have a screen may be a bugbear for some. The maker says this is a positive [as it creates no distractions] but it means you have to wear something else to tell the time or receive alerts. It also doesn’t include an estimate of VO2 max [aerobic capacity, a sign of fitness], which fitness enthusiasts may want.’
7/10
Garmin Venu 3s
£449.99, garmin.com
The Garmin Venu, can even track you when you are swimming
Features: Tracks steps, sleep, daytime naps, heart rate, HRV, post-exercise recovery, stress, blood oxygen, VO2 max, skin temperature, respiration rate, intensity of activity and 30 pre-loaded sports and activities, including cycling and boxing. It has GPS for running and more.
My verdict: Whether you run, swim or do yoga, this can track it. The efficient GPS loads quickly, so you can see how far and what route you’ve run (or hiked, or walked) and in the pool (it’s waterproof to a depth of 50metres) it tracks laps effectively. It also tells you how you’ve slept (and factors naps into your sleep need that night), and how you recover from exercise.
I liked the fact that it counted the ‘recovery hours’ my body needed after a workout. It can be easy not to give your body time to recover between sessions, increasing injury risk.
It’s also a smartwatch, so you can use it to take calls and messages in place of your phone.
Expert verdict: ‘This is very inclusive as it offers built-in workouts for wheelchair users and tracks wheelchair pushes,’ says Dr Kingsnorth. (He tracks his swim sessions with a Garmin.) ‘The battery life is decent [a week to ten days] and it charges in less than two hours.’
9/10
ScanWatch Nova
£549.95, withings.com
The ScanWatch Nova looks more like a traditional watch, so could tempt you to wear it more often, says Dr Kingsnorth
Features: Tracks steps, sleep, overnight breathing disturbances, heart rate, ECG for atrial fibrillation (abnormal heartbeat), blood oxygen, VO2 max, skin temperature, menstrual cycles, 40 pre-loaded activities and more.
My verdict: The most expensive device I tried, but it looks and feels it. Unlike other wristbands, this looks just like any other dress watch. This makes it heavier, but it has an alternative silicone sports band when you exercise.
The app allows you to download a detailed PDF of all your health data, which you could share with your doctor or coach.
Expert verdict: This watch can provide ECG and blood oxygen saturation measurements, ‘although these won’t be of particular interest to most people day to day’, says Dr Kingsnorth.
‘The analogue appearance might make you wear it more often – alongside its long, 30-day battery life. And consistent use is one of the most important factors.’
9/10
Oura Ring 4
From £349, johnlewis.com
The Oura ring may suit your lifestyle better than a watch-type device
Features: Tracks steps and activity levels, sleep, sleep stages, heart rate, blood oxygen, illness detection (using shifts in temperature and heart rate), stress, menstrual cycles and more.
My verdict: I wore this gold ring on my little finger and it was fairly unobtrusive. I liked the fact it takes into account the fact I am pregnant – part of its menstrual cycle tracking feature – and that its sleep health metrics even tell you whether you are a natural lark or an owl.
However, you have to pay £5.99 a month to access all but its most basic features after paying for the ring. It also might be uncomfortable if you are doing a manual job.
Expert verdict: ‘I wore an Oura for about a month to test it out – and liked the fact that I wore it more often because I wasn’t worried about it getting wet or damaged compared with a watch with a fragile screen – and the battery lasted longer [eight days],’ says Dr Kingsnorth.
‘However the workout information was not up to the standard of the wrist-worn devices. When I stopped my subscription I lost access to all my data – a real downside.’
6/10
Polar Vantage M3
£349, polar.com
Features: Tracks steps, sleep and recovery, heart rate, calories burned, training load monitoring, 150 pre-loaded activities, maps, GPS and more.
My verdict: One for die-hard fitness fanatics. It offers feedback on how strenuous a training session was, which it works out using the heart rate measurement plus a sport-specific calculation to estimate muscle fatigue. However, it was the least comfortable tracker to wear in bed because, although it’s worn round your wrist, it’s rather bulky.
Expert verdict: ‘Wearers can download maps to use offline on the watch – useful for not getting lost,’ says Dr Kingsnorth, ‘and it claims to be able to measure ‘training strain’ including cardio and muscle loads and running power.
‘It is very much a sportsperson’s watch, while most of the other trackers which are tested here straddle lifestyle and fitness.’
8/10
Ultrahuman Ring AIR
£329, ultrahuman.com
Features: Tracks steps, distance, sleep, calories, heart rate, HRV, stress, VO2 max, skin temperature and has an atrial fibrillation detection feature and more.
My verdict: This ring offered some unexpected insights – including alerting me to my daily ‘caffeine permissible window’. Based on my sleep patterns and wake time, it recommended the optimum time of day when coffee would ‘enhance mental clarity and boost productivity’.
Yesterday, my ‘window’ opened at 10.04am and closed at 2.54pm. The app also suggested the best time of day to get outside in the sunlight to help me sleep better that night. If you’re looking for a ring-style tracker, I’d pick this model over the Oura – looks wise, they’re nearly identical, but there’s a subscription for the Oura. Once this ring is purchased, your data is accessible for life.
Expert verdict: ‘Like many other trackers, it also provides an estimate of calories burned, taking into account heart rate data and movement,’ says Dr Kingsnorth.
‘I like the lack of subscription and it’s lighter than the Oura, which could mean it’s more comfortable to wear for a long time.’
8/10
How does the original Fitbit compare?
Fitbit Charge 6, £99.99, store.google.com
Features: Tracks steps, sleep, heart rate, blood oxygen, VO2 max, skin temperature, stress, GPS, 40-plus pre-loaded activities and more.
My verdict: I first tried a Fitbit over a decade ago and it hasn’t changed much since.
It’s a great basic option and the cheapest of the bands I tested. The silicone band is super light on the wrist, but not especially good-looking.
Expert verdict: ‘This is a more fitness-based, rather than health, wearable,’ says Dr Andrew Kingsnorth, of Loughborough University. ‘You can also use it to pay for things, so you don’t need to take your wallet or phone with you when exercising.’
6/10
