Sleepwise™ guide to daytime alertness

Note that you need to have at least five sleep results within the last seven days in order to see your Boost from sleep forecasts. In case you haven't worn your watch or if the sleep tracking was not successful, you can also add sleep times manually in the app to increase your sleep result count.

To see your Boost from sleep forecasts in the Polar Flow app, choose Boost from sleep from the menu or get a glance of the daily Boost from sleep forecast from the card in the Diary. Tapping the card opens the daily Boost from sleep view.

Boost from sleep view opens:

In the morning, you can see a forecast for how your sleep boost is expected to vary throughout the day, and plan alertness boosting activities accordingly (such as naps, coffee, or a walk outside). This provides simple visual and numeric feedback on any changes in your sleep rhythm. This way, you can easily recognize if the changes are for better or for worse. This helps helps you understand how the effects of sleep accumulate in the long run. It makes the impact of sleep debt and irregular sleep-wake rhythm visible.

Boost score summarizes the daily forecast into one number in order to make it easy to compare between days. Your boost score may be excellent, good, fair, or modest. Excellent boost score means that you get all the benefits of good sleep to support your day. Your boost score may be modest if you, for example, have a lot of sleep debt. You might see repeating patterns in the trend, for instance, because of weekends.

The daily Forecast graph shows how your recent sleep is expected to boost you throughout the day.

The lighter the shade and higher the bar, the higher the boost level. It means you're likely to feel sharp and ready to perform. The darker the shade and lower the boost. It means you may feel less alert – even drowsy.

Boost levels

Please notice that our forecast is based on sleep only. It doesn't react to anything else you might or might not do during the day. In other words, the graph won't react to the cups of coffee you might consume or the cold showers or brisk walks you might take. Inner motivation also plays a role in how sharp you feel. No matter how high your sleep-based boost level, you're likely to start feeling drowsy during the course of a very boring lecture. On the other hand, you might feel quite sharp even after a bad night's sleep, if you have a truly interesting task at hand. By following the daily forecast, you'll learn that your boost level tends to dip in the afternoon for some time and then go up again. There's no reason to worry about this afternoon slump though. It's regulated by your internal rhythm and is natural to all human beings. By studying the course of your past forecasts, you can learn how today's boost levels are not only affected by last night's sleep but also your recent sleep history. Staying up late on weekends, for example, can affect several days.

Sleep gate anticipates the time when your body is ready to fall asleep. However, your body's internal rhythm might not always align with your everyday commitments. That's why your sleep gate is not always your ideal bedtime in real life. This could be the case, for example, when you go back to work after a break – be it a longer vacation or just a weekend break.

When your watch detects that you've woken up, it will show your Boost from sleep forecasts on the Boost from sleep view. Navigate to the Boost from sleep view by swiping left or right from the watch face.

You can also stop the sleep tracking manually if you watch has not yet summarized your sleep. Zzz is shown on the Boost from sleep view when your watch has detected a minimum of four hours of sleep. Already awake? appears if you tap the display. Confirm by tapping and the watch summarizes your sleep instantly.

In the Weekly sleep view you can compare and analyze your Sleep details from different nights. Tap the calendar icon to access it.

Boost from sleep graph shows how your sleep has affected your days lately. Based on this, you can consider making changes to your sleep schedule.

Sleep & Internal rhythm graph shows how much your actual sleep rhythm deviates from your body's internal circadian rhythm. Syncing these two rhythms – actual and internal – has many health benefits. Sticking to regular bedtimes and wake-up times can help you sync them. You can see how your behavior affects your internal rhythm. For example, staying up late on weekends or traveling over time zones may upset the sync of your rhythms.

Sleep gate anticipates the time when your body is ready to fall asleep. This may be clearly recognizable from your data or not. Irregular sleep rhythm or unusual sleeping hours can mess your internal rhythm and make sleep gate less prominent.

Sleep gate recognizability

You can expect your sleep gate to be clearly recognizable (3/3), if your sleep rhythm is regular. In case your sleep rhythm changes drastically, your sleep gate is difficult to recognize.

Internal rhythm

Your body's internal rhythm means there are times when your body naturally wants to be asleep or awake. The purple lines in the graph show your sleep window – the time span when your body would've naturally wanted to be asleep. The blue bars show your actual sleep rhythm. Syncing these two rhythms – actual and internal – has many health benefits. Sticking to regular bedtimes and wake-up times can help you sync them.

Many people working office hours tend to stay up late and sleep in on weekends. This is how they end up shifting their sleep gate towards staying up late on Sunday night as well. In this very typical case of social jet lag, trouble falling asleep on Sunday night may result in starting a new working week sleep-deprived. Going by the book, the trick to avoid Sunday insomnia and sleep-deprived Mondays is to go to bed and get up at the same time every day. However, if you've ended up staying up late, you should rather compensate that with a nice early afternoon nap instead of sleeping in.

Polar SleepWise feature utilizes sleep tracking and biomathematical modeling for predicting daytime alertness based on how one has slept recently. To predict how sleep boosts one’s alertness, Polar model evaluates sleep amount, quality, and timing against personal sleep need and one’s body’s internal circadian rhythm. The model predicts one's boost levels hour-by-hour, daily boost score, sleep gate, and sleep window. A sleep gate marks the start of one's sleep window - the time when one's body would naturally want to be asleep. It takes from 1 to 2 weeks for SleepWise to collect enough data to reach full reliability.

Biomathematical modeling is a generally accepted means to predict how different sleep schedules impact on alertness during waking hours. Several biomathematical models have been introduced in the scientific literature. While the details and terminology between the models differ, the models typically consider time awake, sleep-wake history, and the circadian rhythm. The outputs of the models have typically been validated against a psychomotor vigilance task after modest or severe sleep restrictions. The psychomotor vigilance task is a simple task where one presses a button as soon as the light appears on a screen. Results from such a task correlate with maintaining attention, problem solving, and decision making.