AutoSleep's readiness rating considers your heart rate variability and waking pulse to give insights into your mental & physical state. Your waking pulse is captured automatically. For a HRV measurement you have a couple options, both are explained more in the sections below.
AutoSleep combines these two amazing health metrics and simplifies them to a simple star rating and an easy to read gauge in the Watch app and the Today tab and Clock tab on the iPhone app. The rating will give you a strong indicator of the day's physical and mental performance potential as well as giving insight into whether you have been pushing things too hard.
About Waking Pulse
This is your heart rate in beats per minute upon waking. It's the gold standard way of capturing your resting heart rate as it is done under controlled and consistent conditions. This lets you easily identify trends. The good news is that if you wear your Watch to bed, AutoSleep does this for you automatically.
Generally speaking, if your heart rate is higher than your established baseline average then you are likely to be more stressed. If lower, then less stressed. Stress may come in many forms, it may be due to illness, decreased fitness, lack of recovery, mental stress, overtraining or many other factors.
About Heart Rate Variability (HRV)
It's a common misconception that a healthy heart always beats like a metronome, every beat in perfect time. In reality, this is what happens when we are more physically or mentally stressed. When we are not physically or mentally stressed, the heart tends to have a more significant beat to beat variation. From a rhythm perspective, it's a bit more like Elaine's famous dance rather than the The Temptations.
How to Record Waking HRV
There's a surprisingly easy and pleasant way to capture HRV. Upon waking, do a 1 minute session using the Breathe app on your Apple Watch (note that since WatchOS 8, the breathe app is now found in the Mindfulness app on your Apple Watch). The best way is to set this up as a complication on your sleeping watch face.
When capturing HRV consistency is everything. Especially when using the SDNN method that the Apple Watch uses as this tends to reflect both physical and mental stress. When you wake, don't sit up, don't do any vigorous movement, just start the Breathe app session whilst lying down, close your eyes and relax. Don't move. Not only does this ensure maximal consistency of measurement, but it's also a nice way to start the day.
Secondly, there's another option for folk that just find using the Breathe app a bit too much in the morning. In this case, AutoSleep will use the automatic HRV capture that your Watch performs during sleep, choosing the most appropriate reading depending on whether you usually reach peak HRV in early or late sleep. This varies depending on how you are "wired".
The Breathe session on waking is still the preferred option, but choices are good aren't they. If you do prefer to ignore the automated sleeping HRV readings, you can enable Waking HRV measurements only in your Readiness score by switching this on in the advanced settings.
What's a Good HRV Measurement?
HRV is reported in milliseconds. There is no point in comparing your reading with someone else. There's also no point in comparing the readings to those taken at other times during the day. It means next to nothing. The value comes over time. AutoSleep will start to determine your baseline HRV measurement. The value comes from comparing your day to day changes (acute) against your baseline (chronic). Generally speaking, if your HRV reading is above your baseline it means you are less stressed. If below the baseline it means you are likely more stressed.
Ideally, you should capture HRV every morning. At a minimum 5 morning's a week will give acceptable results.
AutoSleep's sleep bank uses an advanced algorithm over your last 7 night's sleep to determine if you are in sleep credit or sleep debt. Sleep debt is the difference between the amount of sleep that you should be getting and the amount that you actually get. It starts to quietly build if you regularly miss a few extra minutes of sleep for a few nights in a row and can go easily unnoticed.
If you aim to stay in the "green" (credit) you will generally feel healthier and more alert during the day. Remember you need a good weeks worth of sleep data banked for the Sleep Bank to be fully operational.
You can touch and slide your finger on the Sleep Bank graph to see a pop-up with extra information, showing your current sleep balance as well as the exact hours and minutes that you gained or lost on your sleep bank in that sleep session. This is an amazing way to track your sleep bank.
To help stay in credit, the AutoSleep Today view has a "latest bedtime" clock. This considers your current sleep bank balance, your sleep efficiency and your most likely wake time for the next morning and lets you know the latest time you should be in bed, it can even send you one or more reminders prior to this time! Refer to the Today section for more information on 'Latest Bedtime'.
The sleep bank helps you to monitor your sleep debt. Paying back the debt can be done via a few night's of recovery sleep. When the sleep debt is erased, your body will usually arrive at a consistent sleep pattern that works for you. You can then stay on top of this with the sleep bank and sleep hygiene trends.
Research on Banking Sleep
Symptoms of sleep debt include a foggy brain, impaired driving, trouble remembering and lower levels of both mental and physical performance. In the longer term, chronic deprivation leads to health problems such as obesity, insulin resistance and heart disease.
Though certainly not best sleep hygiene practice, sometimes life isn't as consistent as the textbooks dictate. A number of interesting studies have been undertaken on banking sleep prior to planned sleep deprivation.
Sleep SpO2 (Blood Oxygen)
The Apple Watch Series 6 measures oxygen on the outer area of your wrist (or peripherally), so the measurements are given as peripheral oxygen saturation, also known as SpO2. SpO2 represents the percentage of the haemoglobin in your red blood cells that are carrying oxygen from the lungs to the rest of your body.
Research studies have shown that the average SpO2 during sleep in healthy individuals is 95% to 97%. This drops lower with age to between 93-97% for those over 60.
Enable Oxygen Saturation Permission
Oxygen Saturation in the health permissions needs to be on to see SpO2 in AutoSleep. To check:
Go into iPhone Settings, then Privacy, then into Health
Find AutoSleep in the list and make sure that Oxygen Saturation is turned on
Blood Oxygen Setup
Unless the blood oxygen is activated on your Apple Watch, you may find you are not getting any SpO2 measurements overnight, so this is essential for sleep SpO2 monitoring.
For best results, ensure you enable all 3 settings in the Watch settings app (black icon with image of a Watch) in the Blood Oxygen section. Ensure that the 2 switches are enabled under 'Allow Background Measurements', as these may be turned off by default (see image below showing the correct setup). This allows measurements while you sleep.
Note: Apple states that measurements taken with the Blood Oxygen app are not intended for medical use and are only designed for general fitness and wellness purposes. We have tested internally with clinical blood oxygen devices and found the results to be extremely accurate.
Provided you have the above blood oxygen switches all on, the Sleep SpO2 section will show your average SpO2 % for the nights sleep, along with the minimal and maximum SpO2 measurements. We have found that the Apple Watch will collect anywhere between 10-20 SpO2 measurements a night, depending on your sleep duration, activity and Watch positioning. Refer to the Sleep graph to see all your SpO2 recordings during the night.
Tap on the Sleep SpO2 section to see your trends over a period of time, including maximums, minimums and rolling averages. An SpO2 Report will display showing your current average along with a 7 day and 28 day average so you can accurately track your measurements.