Deep sleep, also referred to as slow wave sleep (SWS), is one of 4 stages of sleep (light, deep, REM and wake) that you spend time in each night. It is known as the “physically restorative” stage of sleep, and is of great importance for athletes and anyone looking to perform at their best on a daily basis.
As stated above, deep sleep is when your body restores itself physically. The vast majority of human growth hormone (95%) is actually produced at this time. Something many people don’t realize is that you don’t actually get stronger at the gym or when you’re exercising. Your muscles break down while you’re working out, then they are built back up again during deep sleep. Getting enough deep sleep is essential for maximizing potential gains from your training that day.
Any efforts you can make to improve your overall sleep behavior will tend to benefit your deep sleep as well. The most basic thing to do is simply spend more time in bed. Here are 45 tips for better sleep, as well as some suggestions from the National Sleep Foundation.
In general, deep sleep usually consists of 15-25% of most adults’ total time asleep. So to reiterate the point above, when our members log in the WHOOP Journal that they sleep in their own bed (as opposed to somewhere else), on average they get 15 additional minutes of total sleep, with 3 minutes of that (20%) being deep sleep (labeled SWS in the chart below)–a proportional increase in deep sleep along the lines of what should be expected.
Data from our journal feature also shows that things like proper hydration during the day (+6 minutes total sleep, +1 minute SWS), wearing a sleep mask and using a sound machine (both +5 minutes total sleep and +1 minute SWS) all correlate with a similarly proportional increase in total sleep and deep sleep.
However, we have observed that some sleep-promoting behaviors specifically boost deep sleep at a higher-than-expected ratio when compared to overall sleep time…
The following things logged in the WHOOP journal have a negative correlation with deep sleep:
Additionally, consuming alcohol before bed can be extremely detrimental to deep sleep. When your body is forced to process alcohol during sleep it has trouble getting beyond light sleep and into deep sleep.
A data analysis of sleep consistency (going to bed and getting up at similar times every day) from 25,000 WHOOP members showed a clear rise in nightly deep sleep as the percentage of sleep consistency over a 4-day period went up:
Sleep consistency helps maintain your circadian rhythm, the body’s 24-hour internal clock. When your body is on a predictable schedule it runs more efficiently and can better anticipate the onset of sleep each night, which in turn benefits your deep sleep.
Learn more about WHOOP sleep tracking and how we measure sleep.