A good night’s sleep is the foundation of health, fitness and wellbeing. The quantity and quality of the zzz's we get has a huge impact on everything from our stress levels and mental health to body composition and weight. It even affects our emotional intelligence and decision making, and can hamper our efforts to make fitness gains.
It’s no surprise then that in recent years all the major fitness tracker, sports watch and smartwatch makers have ramped up their sleep-tracking credentials in a bid to help us better understand our sleep patterns.
Essential reading: Best Garmin watches to buy now
Among them is Garmin. For a long time its rudimentary sleep tracking was frankly not worth paying much attention to. But in 2018, Garmin launched its Advanced Sleep Monitoring features, and finally made a bid to catch up with the likes of Fitbit. Watches like the Forerunner 245, Fenix 5 and Vivosmart 4 started to deliver detailed insights into our bedtime habits and offer a more holistic view of our fitness.
So how does this latest version of Garmin sleep tracking work? And what’s the best way to get the most out of it? Here’s everything you need to know.
Read this: The best Garmin deals
How does Garmin sleep tracking work?
In the past, Garmin devices used movement – tracked by motion sensing accelerometers – and heart rate, using the built-in optical heart rate sensor, to analyse your sleep.
Read this: Best sleep trackers compared
But Advanced Sleep Monitoring now also factors in heart rate variability — the time between each heartbeat – to better measure your time awake and time spent in each sleep stage.
In order to assess whether you’re awake reading, asleep or up for a 3am toilet break, and which stage of sleep you’re in while you slumber, Garmin uses a combination of analysis of photoplethysmography (PPG) and actigraphy (ACT) data. That takes into account the following:
- Changes in heart rate; your heart rate data is more erratic in REM sleep and lower in non-REM sleep, for example.
- Changes in heart rate variability; a rise in HRV can indicate your body is in a stressful situation even when you’re asleep.
- Movement spotted by the accelerometer.
Your ‘sleep clock’ is triggered to start when you get into bed and your heart rate drops to the levels the watch knows you sleep at. Based on your HRV this becomes more accurate the longer you wear the watch.
Other things that might affect the accuracy include stress, sleepwalking or if you’ve drunk alcohol, where your heart rate is raised and you’re potentially moving a lot.
What’s also interesting here is that Garmin Advance Sleep doesn’t track naps. There’s plenty of research to show the benefits of napping and it’s something elite athletes are encouraged to do, so it’s a very important part of the sleep picture. But the app takes into account the length of sleep so if you doze off on the sofa after a long run or ride on a Sunday afternoon, and you only nap for one hour, it won't pick it up, despite the physiological signs the watch should be spotting. Though your cheeky snoozing will recharge your Body Battery score.
It’s also important to note that while some Garmin devices (Vivosmart 4, Fenix 5 Plus series, Forerunner 245, Forerunner 945) also now measure Pulse Oximetry and can spot changes in blood oxygen – SpO2 – levels, this isn’t used to determine the sleep cycle tracking.
How to get the most accurate sleep data with your Garmin
We won’t delve into the accuracy debate here, but to ensure you’re getting the most accurate sleep data possible from your Garmin, you need to:
- Wear your device at least two hours before bedtime and keep it on while you sleep.
- Make sure your device’s heart rate monitor is on, and the device fits snugly but comfortably.
- Set your watch as your Preferred Activity Tracker.
Digging into your data: What Garmin sleep reveals
Each morning you get a full, nightly readout that reveals how much sleep you got in total, along with a breakdown of the time spent in different sleep stages: Deep, Light and REM and also the duration of any periods where you’re awake.
Sleep stats aren’t shown on the watch itself, but we’re told this is coming in an update. To delve into the detail you need to fire up the Garmin Connect app or web tools.
In the app, you can add a widget to get your most recent sleep time displayed on your My Day screen. You can get the full sleep breakdown by hitting More and then tapping into your Health Stats. This is also the best place to review your sleep data in the web tools.
Your data is presented in a timeline that shows you when you fall asleep and when you wake up rather than when you get into and out of bed. If you know there’s an error here, you can manually edit these times in the Garmin Connect app and on the Garmin Connect web tools.
You also get a Movement timeline that shows your movement while you’re asleep and a Pulse Ox timeline that shows the level of oxygen in your blood or SpO2. An SpO2 that’s outside of the normal 95-100% range, and particularly below 90%, can be a sign of health issues, including sleep apnea.
A seven-day view shows your averages for a given week but there are limitations here. Consistent bed and wake times are an important factor for good sleep hygiene and rather than just seeing the duration of sleep for a seven night period, this view could easily be improved by showing the times you went to sleep and woke alongside each other, making it easy to spot how consistent you are.
Similarly, you can set sleep time goals but going into Settings > User Settings in the Garmin Connect app, and adjusting your Normal Bed Time and Normal Wake Time. However, you don’t get feedback on whether you stuck to your bedtime and wake times. It would be handy to have an optional 30 minute warning to alert you when it’s nearing time for bed too, so you don’t load up that next episode on Netflix.
Garmin uses sleep data for its new Body Battery feature
Another omission here is separating out the time it takes to fall asleep after you get into bed and the time to get out of bed once you’re awake. Hitting snooze is the enemy to good sleep habits, and it’d be useful to see how long you doze in bed after you first wake as you get with some other sleep-tracking devices.
A word of warning – and a slightly worrying nod to accuracy – you will still get a sleep report for the night if you leave your watch on charge and this will skew your weekly averages. The best way to spot this in your stats, is when there’s no Pulse Ox data. Sadly there’s no way to delete these rogue readings or let Garmin know you weren’t wearing your watch.
On newer, top end Garmin watches, alongside stress and activity data, sleep stats now also feed into another metric called Body Battery. Body Battery is basically a score from 0-100 that represents how well recovered and energised you are at any given moment. After a decent night’s sleep you’re aiming for this body battery to be full.
How we test