A new beta firmware update for the Fenix 8, Forerunner 970 and Forerunner 570 brings Garmin’s sleep alignment and optimal sleep window feature to more users. The tools first appeared on the Venu 4 and aim to bridge the gap between how much rest you get and how much your body actually needs.
Garmin goes deeper on sleep timing, not just sleep tracking
Garmin already offers a fairly comprehensive set of sleep features. Its watches track sleep stages, score your nightly rest, and suggest how much sleep you need based on your recent activity. The new alignment and optimal window tools build on that foundation by shifting the focus from quantity to timing.
This feature set is built around one central idea. We have an internal clock that governs when we naturally feel alert or sl…
A new beta firmware update for the Fenix 8, Forerunner 970 and Forerunner 570 brings Garmin’s sleep alignment and optimal sleep window feature to more users. The tools first appeared on the Venu 4 and aim to bridge the gap between how much rest you get and how much your body actually needs.
Garmin goes deeper on sleep timing, not just sleep tracking
Garmin already offers a fairly comprehensive set of sleep features. Its watches track sleep stages, score your nightly rest, and suggest how much sleep you need based on your recent activity. The new alignment and optimal window tools build on that foundation by shifting the focus from quantity to timing.
This feature set is built around one central idea. We have an internal clock that governs when we naturally feel alert or sleepy. Garmin now tries to identify this circadian rhythm and compare it to your actual sleep habits. The goal is to uncover whether your lifestyle and biological rhythm are in sync.
Essential reading: How to use Garmin’s new Battery Manager on Fenix 8 and Enduro 3
Most people sleep based on external cues like alarms or work shifts. This often leads to a mismatch between their schedule and what their body prefers. That gap is sometimes called social jet lag. It can leave you feeling drained even after a full night of sleep. Garmin’s sleep alignment feature is designed to detect that misalignment and help you gradually shift toward a better rhythm.
What these two features actually do
Garmin splits this into two related tools. Sleep alignment shows how closely your actual sleep matched your inferred biological preference. The optimal sleep window is the guidance system. It suggests when you should ideally go to bed and wake up.
One tells you how you did. The other tells you what to aim for.
Over time, the watch generates a consistent timing band. This might be something like 22:10 to 06:10. That window becomes your baseline. If your sleep falls within it, alignment is high. If you regularly go to sleep outside of it, your alignment score drops. Garmin does not publish its exact method, but various clues suggest it uses multi-day inputs and resists sudden shifts.
It takes about three weeks to establish a baseline. Once enough data has been collected, the watch starts displaying both your actual sleep window and your inferred optimal window. When the two lines overlap, your alignment is good.
This is not a rigid coaching system. If your body clock wants you asleep at midnight but your life demands 6 a.m. wakeups, the system doesn’t scold you. It simply shows where the difference lies. Garmin encourages users to shift slowly, 15 minutes at a time, if they want to improve alignment.
The system does not respond instantly to travel, late nights or changes in schedule. Instead, it adapts slowly to reflect long-term physiology, not just clock time.
Garmin’s model likely uses your recent sleep, activity and a combination of physiological inputs to arrive at these metrics. Skin temperature typically drops before sleep and rises before waking. HRV fluctuates across the day and can indicate stress or recovery. Activity levels also shift the body’s need for rest. All of this contributes to how the watch identifies your preferred rhythm.
Where to find the data
On the watch, sleep alignment appears in the Sleep glance. The recent Beta 21.12 firmware release adds this to the Fenix 8 series, Enduro 3, Fenix E and Tactix 8. The Beta 16.11 for the Forerunner 970 and 570 also brings this feature.
In addition to the glances, you will see optimal sleep window guidance in the morning report. And, of course you can find some of this info in Garmin Connect.
Some Venu 4 users report that sleeping within the suggested window results in more stable HRV and better Body Battery recharge. Others have noticed no major impact, particularly if they already had good sleep habits. It is likely that the feature offers the most value to those with inconsistent sleep timing or irregular schedules.
There’s nothing particularly novel about these new features. Whoop, Ultrahuman, RingConn and a few other brands have had them for a while. It’s good to see Garmin closing this gap. Hopefully, the company will bring the new sleep tools to other older watches as there is nothing special here needed as far as sensors.
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