There are 4 stages of sleep that your body experiences each night (usually spanning 3-5 sleep cycles): Light sleep, deep sleep (also referred to as slow wave sleep or SWS), REM sleep and awake. For a more in-depth explanation of how this works, check out Understanding Sleep Cycles and the Stages of Sleep.
Below we’ll give a brief overview of the 4 sleep stages, then break down what’s normal for how much time you should be spending in all of them.
Light sleep occurs as you transition to deep sleep. It has minimal restorative impact and you can be easily awakened during it. Your body is more responsive to its environment in this stage.
Deep sleep, known as the “physically restorative” stage of sleep, is when your muscles and tissues repair themselves and cells regenerate. The body produces 95% of human growth hormone during this time. It is often difficult to wake up during deep sleep, and when you do you are likely to feel groggy and disoriented.
REM sleep is the “mentally restorative” stage, during which your brain converts short-term memories made during the day into long-term ones. The brain is also very active during REM sleep (REM stands for “rapid eye movement”), and your heart rate and respiratory rate increase. Additionally, it is when your most vivid dreams occur.
This is included as a stage of sleep because it is normal to be awake for several brief periods of time throughout the night while you are “sleeping.” Referred to as arousals (“disturbances” in the WHOOP app), it is common to experience as many as 10-20 over the course of a night’s sleep. They only last for minutes at a time and you’re generally not conscious of them, but they can add up to significant sleep loss.
Read more about the differences between deep sleep and REM.
Below is a graphic depicting the average amount of time WHOOP members spend in each of the 4 stages of sleep on a nightly basis, as well as the percentage of total time each stage represents.
It’s worth noting that for the most part our members are people who are interested in tracking their physiological data 24/7 and improving their overall performance, so it’s likely they make more of an effort to get quality sleep than the general population as a whole.
Every human body is different, and the amount of sleep we need varies from person to person. The middle 50% of all WHOOP members average the following per night:
Looking at the graphic above, if you subtract the time awake from the total, WHOOP members average 7:02 of sleep each night. The middle 50% range between 6:42 and 7:24.
However, there’s obviously a difference between how much sleep people actually get and how much they should get.
The WHOOP Sleep Coach tells you exactly how much sleep you need each night (based on strain your body accumulates during the day, sleep debt left over from previous nights, and any potential naps), and makes recommendations for exactly when to go to bed and wake up in order to optimize your sleep.