When the rhythm of our lives are in sync with our physical rhythms, then the daily stress we encounter can be soothed. Our brains are like machines, recording everything we experienced and learned throughout the day. Similar to formatting a computer, sleep allows us to have a new start. If our brain functions for too long, like a computer, our brains also slow down and cannot be as active as we want it to be. So, if we know how our brains rest during sleep, then we can utilize our sleep to gain more efficiencies for work during the day.

There is a regular pattern in sleep. Our sleep is divided into 4 stages. The 4 stages are divided between REM sleep and non-REM sleep. The first stage, non-REM, prepares us for rest. This is the time before we truly fall asleep. During this stage, we close our eyes and relax our muscles. Our breathing and heartbeat slow down and the temperature of our blood lowers.

The second stage is the stage of shallow sleep. It can last from 1 minute to 10 minutes. During this stage, you can wake up with only a weak stimulus, like someone’s soft touch of your skin.

In the third stage, the brain waves are of higher amplitude. This is usually called slow-wave sleep (SWS), or, more colloquially, deep sleep. The third stage can last from 10-20 minutes, and, during this interval of sleep, one cannot wake up, even from strong stimuli.

Lastly, the fourth stage is a period of shallow sleep, and it continues from 1 to 10 minutes. In this shallow sleep, one can be easily awaken from small stimuli. This REM sleep interval, in which our eyes move very rapidly, lasts for about 20 minutes. Usually, humans repeat this cycle for 4 to 5 times a night.

However, if a person wakes up during the period of REM sleep, even though she sleeps a lot, she will not feel refreshed. And, actually, she will feel more exhausted than when she first slept. So, if our sleep is not interrupted, we can sleep more deeply and more effectively. Even though sleep, like many other things, are different between one individual and the next, one thing is certain—sleeping for the same amount every day, so that our internal clocks have no need to re-adapt to our dynamic sleep schedules. If we are able to continue this pattern of sleep uninterrupted for 4.5 hours, 6 hours, or 7.5 hours, then we can manage our brains very effectively.